LICE (Phthiraptera)

Lice are a menace to humans, pets, and livestock, not only because of their blood-feeding or chewing habits, but also because of their ability to transmit pathogens. The human body louse has been indirectly responsible for influencing human history through its ability to transmit the causative agent of epidemic typhus. However, most of the 3200 known species of lice are ectoparasites of wild birds or mammals and have no known medical or veterinary importance. The order Phthiraptera is divided into two main taxonomic groups: the Anoplura (sucking lice) and Mallophaga (chewing or biting lice). All members of the Anoplura are obligate, hematophagous ectoparasites of placental mammals, whereas the more diverse.

Mallophaga include species that are obligate associates of birds, marsupials, and placental mammals. Although certain chewing lice imbibe blood, most species ingest host feathers, fur, skin, or skin products. Because of the different feeding strategies of the two groups, the blood-feeding Anoplura are far more important than the Mallophaga in transmitting pathogens to their hosts.

TAXONOMY

Major taxonomic syntheses for the sucldng lice include a series of eight volumes by Ferris (1919-1935) that remains the most comprehensive treatment of this group on a worldwide basis. Ferris (1951) updated much of his earlier work in a shorter overview of the group. Kim et al. (1986) have compiled an authoritative manual and identification guide for the sucking lice of North America. Durden and Musser (1994a) provide a taxonomic checldist for the sucking lice of the world, with host records and geographical distribution for each species. The chewing lice are taxonomically less well known than are the sucking lice, and few authoritative identification guides are available. These include a synopsis of the lice associated with laboratory animals (Kim et al. 1973), guides to the lice of domestic animals (Tuff 1977, Price and Graham 1997), and an identification guide to the lice of sub-Saharan Africa (Ledger 1980). These publications provide information on both sucking lice and chewing lice. Checklists of the Mallophaga of the world (Hopkins and Clay 1952) and of North America (Emerson 1972) are useful taxonomic references for this group.

Because of the relatively high degree of host specificity exhibited by both chewing and sucking lice, several host-parasite checklists have been prepared. These include a detailed list of both anopluran and mallophagan lice associated with mammals (Hopkins 1949), a hostparasite list for North American Mallophaga (Emerson 1972), a world host-parasite list for the chewing lice of mammals (Emerson and Price 1981 ), and a host-parasite checklist for the Anoplura of the world (Durden and Musser 1994b).

About 550 species of sucking lice have been described (Durden and Musser 1994a), all of which parasitize placental mammals; these lice are currently assigned to 50 genera and 15 families. About 2650 valid species of Mallophaga have been described; most of these are associated with birds, but about 400 (ca. 15%) parasitize mammals. The Mallophaga can be divided into 3 suborders (Table I), 11 families, and 205 genera.

The Mallophaga are divided into the following three groups (suborders of most authors): Amblycera (seven families, ca. 76 genera, and ca. 850 species), Ischnocera (three families, ca. 130 genera, and ca. 1800 species), and Rhyncophthirina (one family, 1 genus, and 3 species) (Figs. 4.1 and 4.5). However, there has been disagreement regarding the taxonomic rank of these three groups and their relationships to the Anoplura. Many current classifications treat the Phthiraptera as an order and assign suborder (or superfamily) rank to each of the Anoplura, Amblycera, Ischnocera, and Rhyncophthirina. Other classifications treat the Anoplura and Mallophaga as separate orders. Unfortunately, recent phylogenetic analyses of lice based on cladistic principles have produced contradictory results and have failed to resolve this issue. Regardless of current taxonomic interpretations, it is widely agreed that both sucking and chewing lice originated from a common nonparasitic ancestral group closely related to the order Psocoptera (book lice and bark lice). These two groups diverged in the late Jurassic or early Cretaceous Period, 100-150 million years ago.

Sucking lice of medical importance are assigned to two families, the Pediculidae and Pthiridae, whereas sucking lice of veterinary importance are assigned to five families: the Haematopinidae, Hoplopleuridae, Linognathidae, Pedicinidae, and Polyplacidae (Table II). Only one species of chewing louse, the dog biting louse, in the family Trichodectidae, has public health importance. Mallophaga of veterinary significance are typically placed in five families: the Boopiidae, Gyropidae, Menoponidae, Philopteridae, and Trichodectidae (Table I).

Classification and Hosts of Chewing Lice (Mallophaga) of Medical and Veterinary Importance

MORPHOLOGY

Lice are small (0.4-10 mm in the adult stage), wingless, dorso-ventrally flattened insects. The elongate abdomen possesses sclerotized dorsal, ventral, and/or lateral plates in many lice (Fig. 4.2); these provide some rigidity to the abdomen when it is distended by a blood meal or other food source. In adult lice the abdomen has 11 segments and terminates in genitalia and associated sclerotized plates. In females, the genitalia are accompanied by finger-like gonopods, which serve to guide, manipulate, and glue eggs onto host hair or feathers. The abdomen is adorned with numerous setae in most lice. Immature lice closely resemble adults but are smaller, have fewer setae,

(A) Ishnocera; (B)Anoplura; (C)Amblycera; (D) Rhynchopthirina.
FIGURE 4.1 Head and mouthparts ofrepresentatives of each ofthe four principal groups oflice. (A) Ishnocera; (B)Anoplura; (C)Amblycera; (D) Rhynchopthirina. (A, from Price and Graham, 1997; B and D, from Ferris, 1931; C, from Bedford, 1932)

and lack genitalia. After each nymphal molt, the abdomen is beset with progressively more setae, and the overall size of the louse increases.

The male genitalia in lice (Fig. 4.3) are relatively large and conspicuous, sometimes occupying almost half the length of the abdomen. The terminal, extrusable, sclerotized pseudopenis (aedeagus) is supported anteriorly by a basal apodeme. Laterally, it is bordered by a pair of chitinized parameres. Two or four testes are connected to the vas deferens, which coalesces posteriorly to form the vesicula seminalis. In the female, the vagina leads to a large uterus, to which several ovarioles supporting eggs in various stages of development are connected by the oviducts. Two or more large accessory glands, which secrete materials to coat the eggs, and a single spermatheca, in which sperm is stored, are situated posteriorly in the abdomen. Except for the human body louse, all lice cement their eggs, called nits, onto the hair or feathers of their host. Eggs are usually subcylindrical, with rounded ends and a terminal cap, the operculum (Fig. 4.4). On the top of the operculum is a patch of holes or areas with thin cuticle, called micropyles, through which the developing embryo respires. Most of the egg is heavily chitinized, which helps to protect the embryo from mechanical damage and desiccation. A suture of thin cuticle encircles the base of the operculum. At the time of hatching, the first-instar nymph emerges from the egg by cracldng this suture and pushing off the operculum.

In chewing lice, the head is broader than the thorax (Fig. 4.5). Amblyceran chewing lice have four-segmented antennae and have retained the maxillary palps characteristic of their psocopteran-like ancestor. However, ischnoceran chewing lice have three to five antennal segments and lack maxillary palps. In the Amblycera, the antennae are concealed in lateral grooves, whereas in the Ischnocera and Rhyncophthirina, the antennae are free from the head (Figs. 4.1 and 4.5).

There is a gradation in the specialization of the mouthparts and of the internal skeleton of the head, or tentorium, from the psocopteran-like ancestor of the lice through the Amblycera, Ischnocera, Rhyncophthirina, and Anoplura. Although mallophagan lice all possess chewing mouthparts (Fig. 4.6), the components and mechanics of these mouthparts differ for each group. In the Amblycera, the opposable mandibles move in a vertical plane, or perpendicular to the ventral surface of the head, whereas in the Ischnocera they move more or less horizontally. In contrast, the Rhyncophthirina possess tiny mandibles that are situated at the tip of an elongated rostrum (Figs. 4.1D and 4.5F). Through extreme

Classification and Hosts of Sucking Lice (Anoplura) of Medical and Veterinary Importance

modifications, members of the chewing louse genus Trochilocoetes (parasites of humming birds) have evolved mouthparts that can function as sucking organs.

The thorax in chewing lice usually appears as two, and occasionally three, segments. Chewing lice possess one or two simple claws on each leg; species that parasitize highly mobile hosts, especially birds, typically have two claws.

In sucking lice (Figs. 4.2 and 4.7) the head is slender and narrower than the thorax. Anoplura have three- to five-segmented antennae and lack maxillary palps. Eyes are reduced or absent in most sucking lice but are well developed in the medically important genera Pediculus and Pthirus (Fig. 4.7A, B), and ocular points, or eyeless projections posterior to the antennae, are characteristic of sucking lice in the genus Haematopinus (Fig. 4.7E).

As indicated by their name, anopluran mouthparts function as sucking devices during blood feeding

A generalized sucking louse (Anoplura), showing dorsal (left) and ventral (right) morphology.
FIGURE 4.2 A generalized sucking louse (Anoplura), showing dorsal (left) and ventral (right) morphology. (From Ignoffo, 1959.)

(Fig. 4.8). At rest, the mouthparts are withdrawn into the head and are protected by the snoutlike haustellum, representing the highly modified labrum. The haustellum is armed with tiny recurved teeth which hook into the host skin during feeding. The stylets, consisting of a serrated labium, the hypopharynx, and two maxillae, then puncture a small blood vessel (Fig. 4.8). The hypopharynx is a hollow tube through which saliva (containing anticoagulants and enzymes) is secreted. The maxillae oppose each other and are curved to form a food canal through which host blood is imbibed (Fig. 4.9).

In sucking lice, all three thoracic segments are fused and appear as one segment. In most species, the legs terminate in highly specialized claws for grasping the host

Internal abdominal anatomy of a male human body louse (Pediculus humanus humanus).
HGURE 4.3 Internal abdominal anatomy of a male human body louse (Pediculus humanus humanus). (From Ferris, 1951.)
Eggs (nits) of representative lice. (A) Chicken body louse, Menacanthus stramineus; (B) Oval guineapig louse, Gyropus ovalis; (C) Pigeon louse, Columbicola columbae; (D) Cattle biting louse, Bovicola bovis; (E) Elephant louse, Haematomyzus elephantis; (F) Human head louse, Pediculus humanus capitis. (From Marshall, 1981).
FIGURE 4.4 Eggs (nits) of representative lice. (A) Chicken body louse, Menacanthus stramineus; (B) Oval guineapig louse, Gyropus ovalis; (C) Pigeon louse, Columbicola columbae; (D) Cattle biting louse, Bovicola bovis; (E) Elephant louse, Haematomyzus elephantis; (F) Human head louse, Pediculus humanus capitis. (From Marshall, 1981).

pelage. These tibio-tarsal claws consist of a curved tarsal element which opposes a tibial spur (Fig. 4.10) to enclose a space that typically corresponds to the diameter of the host hair.

The internal anatomy of lice (Fig. 4.3) is best known for the human body louse. As in most hematophagous insects, strong cibarial and esophageal muscles produce a sucking action during blood feeding. The esophagus leads to a spacious midgut composed primarily of the ventriculus. The posterior region of the midgut is narrow and forms a connection between the ventriculus and the hindgut. Ventrally, mycetomes containing symbiotic microorganisms connect to the ventriculus.

LIFE HISTORY

Lice are hemimetabolous insects. Following the egg stage, there are three nymphal instars, the last of which molts to an adult. Although there is wide variation between species, the egg stage typically lasts for 4-15 days and each nymphal instar for 3-8 days; adults live for up to 35 days. Under optimal conditions many species of lice can complete 10-12 generations per year, but this is rarely achieved in nature. Host grooming, resistance, molting and feather loss, hibernation, and hormonal changes, as well as predators (especially insectivorous birds on large ungulates), parasites and parasitoids, and unfavorable weather conditions can reduce the number of louse generations.

Fecundities for fertilized female lice vary from 0.2 to 10 eggs per day. Males are unknown in some parthenogenetic species, whereas they typically constitute less than 5% of the adult population in the cattle biting louse and less than 1% in the horse biting louse.

BEHAVIOR AND ECOLOGY

Blood from the host is essential for the successful development and survival of all sucldng lice. Anoplura are vessel feeders, or solenophages, that imbibe blood through a hollow dorsal stylet derived from the hypopharynx (Fig. 4.9). Contraction of powerful cibarial and pharyngeal muscles create a sucking reaction for imbibing blood.

Chewing lice feed by the biting or scraping action of the mandibles. Bird-infesting chewing lice typically use their mandibles to sever small pieces of feather, which drop onto the labrum and are then forced into the mouth. Chewing lice which infest mammals use their mandibles in a similar manner to feed on host fur. Many chewing lice that infest birds and mammals can also feed on other integumental products, such as skin debris and secretions. Some species of chewing lice are obligate, or more frequently facultative, hematophages. Even those species of chewing lice that imbibe blood scrape the host integument until it bleeds. The rhyncophthirinan Haematomyzus elephantis, which parasitizes both African and Asian elephants, feeds in this manner.

Chewing lice (Mallophaga) of veterinary importance, showing dorsal morphology (left) and ventral morphology (right) in each case. Not drawn to scale. (A) Heterodoxus spiniger, male, from carnivores; (B) Tricholipeurus parallelus, female, from New World deer; (C) Sheepbiting louse (Bovicola bovis), female; (D) Dog-biting louse (Trichodectes canis), female; (E) Catbiting louse (Felicola subrostrata), male; (F) Elephant louse (Haematomyzus elephantis), male. (A-E, from Emerson and Price, 1975; F, from Werneck, 1950)
FIGURE 4.5 Chewing lice (Mallophaga) of veterinary importance, showing dorsal morphology (left) and ventral morphology (right) in each case. Not drawn to scale. (A) Heterodoxus spiniger, male, from carnivores; (B) Tricholipeurus parallelus, female, from New World deer; (C) Sheepbiting louse (Bovicola bovis), female; (D) Dog-biting louse (Trichodectes canis), female; (E) Catbiting louse (Felicola subrostrata), male; (F) Elephant louse (Haematomyzus elephantis), male. (A-E, from Emerson and Price, 1975; F, from Werneck, 1950)
Generalized mouthparts of an amblyceran chewing louse (Mallophaga). (A) Ventral view of head; (B) labium and associated structures; (C) mandibles. (Drawn by Margo Duncan)
FIGURE 4.6 Generalized mouthparts of an amblyceran chewing louse (Mallophaga). (A) Ventral view of head; (B) labium and associated structures; (C) mandibles. (Drawn by Margo Duncan)

Symbionts are thought to be present in all lice that imbibe blood. Symbionts in the mycetomes (Fig. 4.3) aid in blood meal digestion, and lice deprived of them die after a few days; female lice lacking symbionts also become sterile. In female human body lice, some symbionts migrate to the ovary, where they are transferred transovarially to the next generation of lice.

Lice in general exhibit host specificity, some to such a degree that they parasitize only one species of host. The hog louse, slender guineapig louse, large turkey louse, and several additional species listed in Tables I and II all are typical parasites of a single host species.

Host specificity is broader in some lice. Some lice of veterinary importance parasitize two or more closely related hosts. Examples include the three species which parasitize domestic dogs: Linognathus setosus, Trichodectes

Sucking lice (Anoplura) of medical and veterinary importance, showing dorsal morphology (left) and ventral morphology (right) in each case. Not drawn to scale. (A) Human body louse (Pediculus humanus humanus), female; (B) Human crab louse (Phthirus pubis), female; (C) Flying squirrel louse (Neohaematopinus sciuropteri), male; (D) Spirted rat louse (Polyplax spinulosa), male; (E) Hog louse (Haematopinus suis), female; (F) Little blue cattle louse (Solenoptes capillatus), male; (G) Dog sucking louse (Linognathus setosus), male; (H) Longnosed cattle louse (L. vituli), female. (From Ferris, 1923-1935.)
FIGURE 4.7 Sucking lice (Anoplura) of medical and veterinary importance, showing dorsal morphology (left) and ventral morphology (right) in each case. Not drawn to scale. (A) Human body louse (Pediculus humanus humanus), female; (B) Human crab louse (Phthirus pubis), female; (C) Flying squirrel louse (Neohaematopinus sciuropteri), male; (D) Spirted rat louse (Polyplax spinulosa), male; (E) Hog louse (Haematopinus suis), female; (F) Little blue cattle louse (Solenoptes capillatus), male; (G) Dog sucking louse (Linognathus setosus), male; (H) Longnosed cattle louse (L. vituli), female. (From Ferris, 1923-1935.)
Head region of a sucking louse (Anoplura) feeding on a host, showing components of mouthparts and associated internal structures. (Original by Margo Duncan.)
FIGURE 4.8 Head region of a sucking louse (Anoplura) feeding on a host, showing components of mouthparts and associated internal structures. (Original by Margo Duncan.)
Cross-section through the mouthparts of a sucking louse (Anoplura). (Original by Margo Duncan.)
FIGURE 4.9 Cross-section through the mouthparts of a sucking louse (Anoplura). (Original by Margo Duncan.)

canis, and Heterodoxus spiniger. These lice also parasitize foxes, wolves, coyotes, and occasionally other carnivores. Similarly, the horse sucking louse (Haematopinus asini), parasitizes horses, donkeys, asses, mules, and zebras, whereas L. africanus parasitizes both sheep and goats. At least six species of chewing lice are found on domestic fowl, all of them parasitizing chickens, but some also feeding on turkeys, guinea fowl, pea fowl, or pheasants (Table I). Lice found on atypical hosts are termed stragglers.

Some sucking lice, such as the three taxa that parasitize humans, the sheep foot louse, and the sheep face louse, are not only host specific, but also infest specific body areas, from which they can spread in severe infestations. Many chewing lice, particularly species that parasitize birds, also exhibit both host specificity and site specificity; examples include several species that are found on domestic fowl, and species confined to turkeys, geese, and ducks (Table I). Lice inhabiting different body regions on the same host typically have evolved morphological adaptations in response to specific attributes of the host site. These include characteristics such as morphological differences of the pelage, thickness of the skin, availability of blood vessels, and grooming or preening activities of the host. Site specificity in chewing lice is most prevalent in the more sedentary, specialized Ischnocera than in the mostly mobile, morphologically unspecialized Amblycera. For example, on many bird hosts, roundbodied ischnocerans with large heads and mandibles are predominately found on the head and neck. Elongate forms with narrow heads and small mandibles tend to inhabit the wing feathers, whereas morphologically intermediate forms occur on the back and other parts of the body.

Some chewing lice inhabit highly specialized host sites. These include members of the amblyceran genus Piagetiella, which are found inside the oral pouches of pelicans, and members of several amblyceran genera, including Actornithophilus and Colpocephalum, which live inside feather quills. Several bird species are parasitized by 5 or more different species of site-specific chewing lice, and up to 12 species may be found on the neotropical bird Crypturellus soul (a tinamou).

Site specificity is less well documented for sucking lice. However, domestic cattle may be parasitized by as many as five anopluran species, each predominating on particular parts of the body. Similarly, some Old World squirrels and rats can support up to six species of sucking lice.

Because of the importance of maintaining a permanent or close association with the host, lice have evolved specialized host-attachment mechanisms to resist grooming activities of the host. The robust tibio-tarsal claws of sucking lice (Fig. 4.10) are very important in securing them to their hosts. Various arrangements of hooks and spines, especially on the heads of lice that parasitize arboreal or flying hosts, such as squirrels and birds, also aid in host attachment. Mandibles are important attachment appendages in ischnoceran and rhyncophthirinan chewing lice. In some species of Bovicola, a notch in the first antenhal segment encircles a host hair to facilitate attachment.

Tibio-tarsal claws and antenna of Linognathus africanis (Anoplura): scanning electron micrograph.
FIGURE 4.10 Tibio-tarsal claws and antenna of Linognathus africanis (Anoplura): scanning electron micrograph. (From Price and Graham, 1997.)

A few lice even possess ctenidia (“combs”) that are convergently similar in morphology to those characteristic of many fleas. They occur most notably among lice that parasitize coarse-furred, arboreal, or flying hosts. Additionally, chewing lice that parasitize arboreal or flying hosts often have larger, more robust claws than do their counterparts that parasitize terrestrial hosts.

Because of their reliance on host availability, lice are subjected to special problems with respect to their longterm survival. MI sucking lice are obligate blood-feeders; even a few hours away from the host can prove fatal to some species. Some chewing lice also are hematophages and similarly cannot survive prolonged periods off the host. However, many chewing lice, particularly those that subsist on feathers, fur, or other skin products, can survive for several days away from the host. For example, the cattle biting louse can survive for up to 11 days (this species will feed on host skin scrapings), and Menacanthusspp. of poultry can survive for up to 3 days off the host. Off-host survival is generally greater at low temperatures and high humidities. At 26~ and 65% relative humidity (RH), 4% of human body lice die within 24 hr, 20% within 40 hr, and 84% within 48 hr. At 75% RH, a small proportion of sheep foot lice survives for 17 days at 2~ whereas most die within 7 days at 22~ Recently fed lice generally survive longer than unfed lice away from the host. Mthough most lice are morphologically adapted for host attachment and are disadvantaged when dislodged, the generalist nature of some amblyceran chewing lice better equips them for locating another host by crawling across the substrate. Amblycerans are more likely than other lice to be encountered away from the host, accounting for observations of these lice on bird eggs or in unoccupied nests and roosts.

Host grooming is an important cause of louse mortality. Laboratory mice infested by the mouse louse, for example, usually limit their louse populations to 10 or fewer individuals per mouse by regular grooming. Prevention of self-grooming or mutual grooming by impaired preening action of the teeth or limbs of such mice can result in heavy infestations of more than 100 lice. Similarly, impaired preening due to beak injuries in birds can result in tremendous increases of louse populations. Biting, scratching, and licking also reduce louse populations on several domestic animals.

Whereas most species of lice on small and mediumsized mammals exhibit only minor seasonal differences in population levels, some lice associated with larger animals show clear seasonal trends. Some of these population changes have been attributed to host molting, fur density and length, hormone levels in the blood meal, or climatological factors such as intense summer heat, sunlight, or desiccation. On domestic ungulates in temperate regions, louse populations typically peak during the winter or early spring and decline during the summer. An exception to this trend is the cattle tail louse, whose populations peak during the summer.

Another important aspect of louse behavior is the mode of transfer between hosts. Direct host contact appears to be the primary mechanism for louse exchange. Transfer of lice from an infested mother to her offspring during suclding (in mammals) or during nest sharing (in birds and mammals) is an important mode of transfer. Several species of lice that parasitize livestock transfer during suclding, including the sheep face louse and the sheep biting louse, both of which move from infested ewes to their lambs at this time. Lice can also transfer during other forms of physical contact between hosts, such as mating or fighting. Transfer of lice between hosts also can occur between hosts that are not in contact. The sheep foot louse, for example, can survive for several days off the host and reach a new host by crawling across pasture land. Nests of birds and mammals can act as foci for louse transfer, but these are infrequent sites of transfer.

Dispersal of some lice occurs via phoresy, in which they temporarily attach to other arthropods and are carried from one host to another (Fig. 4.11). During phoresy, most lice attach to larger, more mobile bloodfeeding arthropods, usually a fly, such as a hippoboscid or muscoid. Phoresy is particularly common among ischnoceran chewing lice. Movement of the mouthparts in a horizontal plane better facilitates their attachment to a fly than in the amblycerans, in which mouthparts move in a vertical plane. Phoresy is rare among sucking lice. This is

Two ischnoceran chewing lice (Mallophaga) phoretic on a hippoboscid fly, attached by their mandibles to the posterior abdomen.
FIGURE 4.11 Two ischnoceran chewing lice (Mallophaga) phoretic on a hippoboscid fly, attached by their mandibles to the posterior abdomen. (From Rothschild and Clay, 1952).

probably because attachment to the fly is achieved by the less efficient mechanism of grasping with the tarsal claws.

Mating in lice occurs on the host. It is initiated by the male pushing his body beneath that of the female and curling the tip of his abdomen upward. In the human body louse, the male and female assume a vertical orientation along a hair shaft, with the female supporting the weight of the male as he grasps her with his anterior claws. Most lice appear to exhibit similar orientation behavior during mating. Notable exceptions include the crab louse of humans, in which both sexes continue to clasp with their claws a host hair, rather than each other, during mating; and the hog louse, in which the male strokes the head of the female during copulation. Some male ischnoceran chewing lice possess modified hooklike antennal segments, with which they grasp the female during copulation.

Oviposition behavior by female lice involves crawling to the base of a host hair or feather and cementing one egg at a time close to the skin surface. Two pairs of fingerlike gonopods direct the egg into a precise location and orientation as a cement substance is secreted around the egg and hair base. Optimal temperature requirements for developing louse embryos inside eggs are very narrow, usually within a fraction of a degree, such as may occur on a precise area on the host body. For this reason, female lice typically oviposit preferentially on an area of the host that meets these requirements.

LICE OF MEDICAL INTEREST

Three taxa of sucking lice parasitize humans throughout the world: the body louse, head louse, and crab louse (pubic louse). All are specific ectoparasites of humans; rarely, dogs or other companion animals may have temporary, selflimiting infestations.

Human head and body lice are closely related and can interbreed to produce fertile offspring in the laboratory. For this reason, they generally are recognized as separate subspecies of Pediculus humanus, as in this chapter. Nevertheless, they rarely interbreed in nature, which has prompted some epidemiologists to treat them as separate species, P. humanus (body louse) and P. capitis (head louse).

Human body louse (Pediculus humanus humanus)

The human body louse (Figs. 4.7A and 4.12) or cootie was once an almost ubiquitous companion of humans. Today it is less common, especially in developed nations. Body lice persist as a significant problem in less developed nations in parts of Africa, Asia, and Central and South America. This is significant because P.h. humanus is the only louse of humans that is known

FIGURE 4.12 Human body lice (Pediculus humanus humanus) feeding on a human. (Courtesy of Elton J. Hansens.)
FIGURE 4.12 Human body lice (Pediculus humanus humanus) feeding on a human. (Courtesy of Elton J. Hansens.)

to naturally transmit pathogens. The large-scale reduction in body louse infestations worldwide has led to a concomitant decrease in the prevalence of human louse-borne diseases. However, situations that result in human overcrowding and unsanitary conditions (e.g., wars, famines, and natural disasters) can lead to a resurgence of body louse infestations, often accompanied by one or more louse-borne diseases.

Adult human body lice (Figs. 4.7A and 4.12) are 2.3-3.6 mm long. Under optimal conditions their populations can multiply dramatically if unchecked; e.g., if clothes of infested individuals are not changed and washed in hot water at regular intervals. In unusually severe infestations, populations of more than 30,000 body lice on one person have been recorded. Body lice typically infest articles of clothing and crawl onto the body only to feed. Females lay an average of four or five eggs per day, and these typically hatch after 8 days. Unique among lice, females oviposit not on hair, but on clothing (Fig. 4.13), especially along seams

FIGURE 4.13 Eggs of the human body louse (Pediculus humanus humanus) attached to clothing. (Courtesy ofElton J. Hansens.)
FIGURE 4.13 Eggs of the human body louse (Pediculus humanus humanus) attached to clothing. (Courtesy ofElton J. Hansens.)ฃ

and creases. Each nymphal instar lasts for 3-5 days, and adults can live for up to 30 days.

Biting by body lice often causes intense irritation, with each bite site typically developing into a small red papule with a tiny central clot. The bites usually itch for several days but occasionally for a week or more. Persons exposed to numerous bites over long periods often become desensitized and show little or no reaction to subsequent bites. Persons with chronic body louse infestations may develop a generalized skin thickening and discoloration called Vagabond disease or Hobo disease, names depicting a lifestyle that can promote infestation by body lice. Several additional symptoms may accompany chronic infestations. These include lymphadenopathy (swollen lymph nodes), edema, increased body temperature often accompanied by fever, a diffuse rash, headache, joint pain, and muscle stiffness.

Some people develop allergies to body lice. Occasionally, patients experience a generalized dermatitis in response to one bite or small numbers of bites. A form of asthmatic bronchitis has similarly been recorded in response to allergy to louse infestations. Secondary infections such as impetigo or blood poisoning can also result from body louse infestations.

Body lice tend to leave persons with elevated body temperatures and may crawl across the substrate to infest a nearby person. This has epidemiological significance because high body temperatures of lousy persons often result from fever caused by infection with louseborne pathogens.

Human head louse (Pediculus humanus cap#is)

The human head louse is virtually indistinguishable from the human body louse on the basis of morphological characters and its life cycle. Unless a series of specimens is available for analysis it is often impossible to separate the two subspecies. Generally, adult head lice are slightly smaller (2.1-3.3 mm in length) than body lice.

As indicated by their name, human head lice typically infest the scalp and head region, rather than other areas of the body infested by body lice. Females attach their eggs to the base of individual hairs. As the hair grows, the eggs become further displaced from the scalp. An indication of how long a patient has been infested can be gleaned by measuring the farthest distance of eggs from the scalp and comparing this to the growth rate of hair.

Today, head lice are far more frequently encountered than body lice, especially in developed countries. Transmission occurs by person-to-person contact and via shared objects such as combs, brushes, headphones, and caps. School-age children are at high risk because they are often more likely to share such items. Some school districts in the United States and Britain have infestation prevalences approaching 50% in students. It has been estimated that 6-12 million people, principally children, are infested with head lice annually in the United States. Some ethnic groups, such as persons of African origin, have coarser head hairs and are less prone to head louse infestations. The reason for this is simply that the tibio-tarsal claws of these lice cannot efficiently grip the thicker hairs.

Although head lice are not known to transmit pathogens, heavy infestations can cause severe irritation. As is the case with human body lice, the resultant scratching often leads to secondary infections such as impetigo, pyoderma, or blood poisoning. Severe head louse infestations occasionally result in the formation of scabby crusts beneath which the lice tend to aggregate. Enlarged lymph nodes in the neck region may accompany such infestations.

Human crab louse (Pthirus pubis)

The crab louse, or pubic louse, is a medium-sized (1.1- 1.8 mm long), squat louse (Fig. 4.7B), with robust tibio-tarsal claws used for grasping thick hairs, especially those in the pubic region. It also may infest coarse hairs on other parts of the body, such as the eyebrows, eyelashes, chest hairs, beards, moustaches, and armpits. This louse typically transfers between human partners during sexual intercourse and other intimate contact; in France, crab lice are described as “papillons d’amour” (butterflies of love). Transfer via infested bed linen or toilet seats can also occur. This is uncommon, however, because crab lice can survive for only a few hours off the host.

Female crab lice lay an average of three eggs per day. Eggs hatch after 7-8 days; the three nymphal instars together last for 13-17 days. Under optimal conditions the generation time is 20-25 days. The intense itching caused by these lice is often accompanied by purplish lesions at bite sites and by small blood spots from squashed lice or louse feces on underwear. Crab lice are widely distributed and relatively common throughout the world. They are not known to transmit any pathogens. One epidemiological study, however, revealed a positive relationship between infection with hepatitis B virus and crab louse infestation.

LICE OF VETERINARY INTEREST

A wide variety of lice infests domestic, livestock, and laboratory animals (Tables I and II). Many hosts, particularly small rodents, often support few if any lice, whereas large hosts such as livestock animals, including poultry, may be parasitized by very large numbers of lice. For example, fewer than 10 mouse lice (Polyplax serrata) on a house mouse are a typical burden, but more than a million lice may be present on extremely heavily infested sheep, cattle, horses, or other large animals.

LICE OF CATTLE

Lice are a major problem in cattle operations worldwide. Domestic cattle are parasitized by six species of lice: three species of Haematopinus, one of Linognathus, one of Solenopotes, and one of Bovicola. Domestic Asiatic buffalo are typically parasitized by H. tuberculatus (Tables I and II).

Females of the cosmopolitan cattle biting louse (Bovicola bovis) lay an average of 0.7 eggs per day, which hatch 7-10 days later. Each nymphal instar lasts 5-6 days, and adult longevity can be as long as 10 weeks. Preferred host sites for this louse are the base of the tail, the shoulders, and the top line of the back, but lice may also populate the pollard in severe infestations.

The longnosed cattle louse (L. vituli) (Fig. 4.7H) also is a worldwide pest. Females deposit about one egg per day, and the life cycle is completed in about 21 days. This louse is most common on calves and dairy stock; it rarely occurs in large numbers on mature cattle. Preferred infestation sites are the dewlap and shoulders; declining spring populations are often confined to the shoulders.

The little blue cattle louse (Solenopotes capillatus) (Fig. 4.7F) also has a worldwide distribution. Females lay one or two eggs per day; oviposition typically causes the hairs on which eggs are laid to bend. Eggs hatch after about 10 days, and adulthood is reached about 11 days later. Clusters of S. capillatus typically occur on the muzzle, dewlap, and neck of mature cattle. Aggregations of this louse may surround the eyes in severely infested animals, giving a spectacled appearance to the host.

The cosmopolitan shortnosed cattle louse ( H. eurysternus) is the largest louse found on North American cattle; adults measure 3.5-4.7 mm in length. Females lay one to four eggs per day for about 2 weeks, nymphs reach adulthood in about 14 days, and adult longevity is 10-15 days. This louse is more common on mature cattle than on young animals. Preferred infestation sites are the top of the neck, the dewlap, and brisket. However, in severe infestations, the entire region from the base of the horns to the base of the tail can be infested. In North America, H. eurysternus is most prevalent in the Great Plains and Rocky Mountain regions.

The cattle tail louse ( H. quadripertusus) parasitizes cattle in the warmer regions of the world. It was inadvertently introduced into the United States, where it now occurs in the Gulf Coast states. Females of this louse oviposit on the tail hairs, which become matted with eggs in severe infestations. Infested tail heads may be shed under these circumstances. Eggs hatch after 9-25 days, depending on the season. Under optimal conditions, the entire life cycle can be as short as 25 days. Nymphs migrate over the host body surface, but adults are typically confined to the tail head. Unlike other cattle lice, H. quadripertusus is most abundant during the summer.

Except for H. quadripertusus, cattle lice increase in numbers during the winter and early spring in temperate regions. During summer, lice persist on 1-2% of the members of a herd; these chronically infested animals typically reinfest other herd members during the winter. Bulls and older cows often serve as reservoirs of lice. Bulls have longer, thicker hair and massive shoulders and neck that compromise self-grooming. During summer, a small number of lice can survive on the cooler ear tips, where lethal temperatures are rarely reached.

LICE OF OTHER LIVESTOCK ANIMALS

Horses, donkeys, hogs, goats, and sheep are parasitized by one or more species of louse (Tables I and II). Except for hogs, all of these animals are parasitized by both sucking lice and chewing lice. The horse biting louse (B. equi) is the most important louse of equids worldwide. Females of this louse oviposit on fine hairs, avoiding the coarse hairs of the mane and tail. This louse typically infests the side of the neck, the flanks, and tail base but can infest most of the body (except the mane, tail, ears, and lower legs) in severe infestations. Longhaired horse breeds are more prone to infestation by B. equi.

Domestic swine are parasitized by the hog louse (H. suis) (Fig. 4.7E). This is a large species in which adult females measure ca. 5 mm in length. Hog lice usually frequent skin folds of the head (especially the ears), neck, shoulders, and flanks of swine. Female hog lice lay an average of 3.6 eggs per day. These are deposited singly on hairs along the lower parts of the body, in skin folds on the neck, and on and in the ears. Eggs typically hatch 13-15 days later; each nymphal instar lasts 4-6 days. Adult hog louse longevity can be up to 40 days, and 6-15 generations can be completed per year, depending on environmental conditions.

Domestic sheep and goats are parasitized by several species of sucking lice and chewing lice (Tables I and II). One of these, L. africanus, parasitizes both hosts. Lice of sheep and goats, especially chewing lice, are economically important wherever these livestock animals are farmed, but especially in Australia, New Zealand, and the United States. Females of the sheep biting louse (B. ovis) lay one or two eggs per day and can live for up to 30 days; each nymphal instar lasts 5-9 days. B. ovis mainly infests the back and upper parts of the body but may populate the entire body in severe infestations. This louse causes intense irritation, and infested sheep typically rub against fences and trees, tearing the fleece and greatly reducing its value. Sucldng louse infestations of sheep rarely cause major economic problems.

LICE OF CATS AND DOGS

Domestic cats are parasitized by one species of chewing louse, whereas dogs are parasitized by two species of chewing lice and one species of sucking louse. All four species seem to be distributed worldwide, but none is a common associate of healthy cats or dogs in North America.

The cat biting louse (Felicola subrostrata) (Fig. 4.5E) parasitizes both domestic and wild cats. It may occur almost anywhere on the body. Both the dog biting louse ( T. canis) (Fig. 4.5D) and the dog sucking louse (L. setosus) (Fig. 4.7G) parasitize dogs and closely related wild canids. For example, T. canis also parasitizes coyotes, foxes, and wolves. A second species of chewing louse of dogs is Heterodoxus spiniger (Fig. 4.5A), which evolved in Australasia from marsupial-infesting lice and apparently switched to dingo hosts. It now parasitizes various canids and other carnivores throughout the world. T. can# usually infests the head, neck, and tail region of dogs, where it attaches to the base of a hair using its claws or mandibles. L. setosus occurs primarily on the head and neck and may be especially common beneath collars. H. spiniger can typically be found anywhere on its host.

LICE OF LABORATORY ANIMALS

The principal species of lice that parasitize laboratory mammals have been described by Kim et al. (1973). These lice also parasitize feral populations of their respective hosts. The house mouse (Mus musculus) is often parasitized by the mouse louse (P. serrata). Populations of this louse are typically low, with 10 or fewer lice per infested mouse, unless self-grooming or mutual host grooming is compromised. Eggs of this louse typically hatch 7 days after oviposition. Together the three nymphal instars last only 6 days under optimal conditions, which can result in a generation time as short as 13 days. Domestic rats are often parasitized by the spined rat louse (P. spinulosa) (Fig. 4.7D) and the tropical rat louse (Hoplopleura pacifica). Common hosts include the black rat (Rattus rattus) and the Norway rat (R. norvegicus). The spined rat louse parasitizes these hosts throughout the world, whereas the tropical rat louse is confined to tropical, subtropical, or warm temperate regions, including the southern United States.

Laboratory rabbits are parasitized by the rabbit louse (Haemodipsus ventricosis). This louse originated in Europe but has accompanied its host and been introduced throughout the world.

LICE OF POULTRY AND OTHER BIRDS

At least nine species of chewing lice commonly infest poultry (Table I) in various parts of the world. Individual birds can be parasitized by multiple species, each of which often occupies a preferred host site. The chicken body louse (Menacanthus stramineus) (Fig. 4.14) is the most common and destructive louse of domestic chickens. It has a worldwide distribution and often reaches pest proportions. Adults measure 3-3.5 mm in length. Females lay one or two eggs per day, cementing them in clusters at the bases of feathers, especially around the vent. Eggs typically hatch after 4-5 days. Each nymphal instar lasts about 3 days, and the generation time typically is 13-14 days. These lice are most abundant on the sparsely feathered vent, breast, and thigh regions. Several other chewing lice are pests of poultry more or less throughout the world (Table I). Adults of the shaft louse (Menopon gallinae) measure ca. 2 mm in length, and females deposit eggs singly at the base of the shaft on thigh and breast feathers. Eggs of the wing louse (Lipeurus capon#) hatch 4-7 days after the female has cemented them to the base of a feather. Nymphal stages of this species each last 5-18 days; generation time typically is 18-27 days, and females can live up to 36 days. Females of the chicken head louse (Cuclutogaster heterographus) attach their eggs to the bases of downy feathers. Eggs hatch after 5-7 days, each nymphal instar lasts 6-14 days, and average generation time is 35 days.

FIGURE 4.14 Chicken body lice (Menacanthus stramineus) on a chicken. (Courtesy of Nancy C. Hinlde.)
FIGURE 4.14 Chicken body lice (Menacanthus stramineus) on a chicken. (Courtesy of Nancy C. Hinlde.)

Poultry lice typically transfer to new birds by direct host contact. However, because most species can survive for several hours or days off the host, they also can infest new hosts during transportation in inadequately disinfected cages or vehicles.

PUBLIC HEALTH IMPORTANCE

Three important pathogens are transmitted to humans by body lice. These are the agents of epidemic typhus, trench fever, and louse-borne relapsing fever. Today, the prevalence and importance of all three of these louse-borne diseases are low compared to times when human body lice were an integral part of human life. However, trench fever has emerged as an opportunistic disease of immunocompromised individuals, including persons who are positive for human immunodeficiency virus (HIV).

EPIDEMIC TYPHUS

Epidemic typhus is a rickettsial disease caused by infection with Rickettsia prowazekii. It is also known as louseborne fever, jail fever, and exanthematic typhus. The disease persists in several parts of the world, most notably in Burundi, Democratic Republic of Congo, Ethiopia, Nigeria, Rwanda, and areas of northeastern and central Africa, Russia, Central and South America, and northern China. Epidemic typhus is largely a disease of cool climates, including higher elevations in the tropics. It thrives in conditions of widespread body louse infestations, overcrowding, and poor sanitary conditions. Epidemic typhus apparently was absent from the New World until the 1500s, when the Spanish introduced the disease. One resulting epidemic in 1576-1577 killed 2 million Indians in the Mexican highlands alone. The vector of R. prowazekii is the human body louse. Lice become infected when they feed on a person with circulating /L prowazekii in the blood. Infective rickettsiae invade cells that line the louse gut and multiply there, eventually causing the cells to rupture. Liberated rickettsiae either reinvade gut cells or are voided in the louse feces. Other louse tissues typically do not become infected. Because salivary glands and ovaries are not invaded, anterior-station and transovarial transmission do not occur. Infection of susceptible humans occurs via louse feces (posterior-station transmission) when infectious rickettsiae are scratched into the skin in response to louse bites. R. prowazekii can remain viable in dried louse feces for 60 days. Infection by inhalation of dried louse feces or by crushed lice are less frequent means of contracting the disease.

Transmission of R. prowazekii by body lice was first demonstrated by Charles Nicolle, working at the Institut Pasteur in Tunis in 1909. During these studies, Nicolle accidentally became infected with epidemic typhus, from which he fortunately recovered. He was awarded the Nobel prize in 1928 for his groundbreaking work on typhus. Several other typhus workers also were infected with R. prowazekii during laboratory experiments. The American researcher Howard T. Ricketts, working in Mexico, and Czech scientist Stanislaus yon Prowazek, working in Europe, both died from their infections and were recognized posthumously when the etiologic agent was named. Infection with R. prowazekii is ultimately fatal to body lice as progressively more and more infected gut cells are ruptured. Infective rickettsiae are first excreted in louse feces 3-5 days after the infective blood meal. Lice usually succumb to infection 7-14 days after the infectious blood meal, although some may survive to 20 days. The disease caused by infection with R. prowazekii and transmitted by body lice is called classic epidemic typhus because it was the first form of the disease to be recognized. Disease onset occurs relatively soon after infection by a body louse in classic epidemic typhus. Symptoms generally appear after an incubation period of 10-14 days. Abrupt onset of fever, accompanied by malaise, muscle and head aches, cough, and general weakness, usually occurs at this time. A blotchy rash spreads from the abdomen to the chest and then often across most of the body, typically within 4-7 days following the initial symptoms. The rash rarely spreads to the face, palms, and soles, and then only in severe cases. Headache, rash, prostration, and delirium intensify as the infection progresses. Coma and very low blood pressure often signal fatal cases. A case fatality rate of 10-20% is characteristic of most untreated epidemics, although figures approaching 50% have been recorded. Diagnosis of epidemic typhus involves the demonstration of positive serology, usually by microimmunofluorescence. DNA primers specific to R. prowazekii can also be amplified by polymerase chain reaction from infected persons or lice. One-time antibreak biotic treatment, especially with doxycycline, tetracycline, or chloramphenicol, usually results in rapid and complete recovery. Vaccines are available but are not considered to be sufficiently effective for widespread HSC. Persons that recover from epidemic typhus typically harbor R. prowazekii in lymph nodes or other tissues for months or years. This enables the pathogen to again invade other body tissues to cause disease seemingly at any time. This form of the disease is called recrudescent typhus or Brill-Zinsser disease. The latter name recognizes two pioneers in the study of epidemic typhus: Nathan Brill, who first recognized and described recrudescent typhus in 1910, and Hans Zinsser, who demonstrated in 1934 that it is a form of epidemic typhus. Zinsser’s (1935) book Rats, Lice, and History is a pioneering account of the study of epidemic typhus in general.

Recrudescent typhus was widespread during the 19th and early 20th centuries in some of the larger cities along the east coast of the United States (e.g., Boston, New York, and Philadelphia). At that time, immigrants from regions that were rampant with epidemic typhus, such as eastern Europe, presented with Brill-Zinsser disease after being infected initially in their country of origin. Some of these patients experienced relapses more than 30 years after their initial exposure, with no overt signs of infection with R. prowazekii between the two disease episodes. Because infestation with body lice was still a relatively common occurrence during that period, the lice further disseminated the infection to other humans, causing local outbreaks. The last outbreak of epidemic typhus in North America occurred in Philadelphia in 1877. Today, even recrudescent typhus is a rare occurrence in North America. However, this form of typhus is still common in parts of Africa, Asia, South America, and, occasionally, in eastern Europe. The southern flying squirrel ( Glaucomys volans) has been identified as a reservoir of R. prowazekii in the United States, where it has been found to be infected in Virginia during vertebrate serosurveys for Rocky Mountain spotted fever. Since the initial isolations from flying squirrels in 1963, R. prowazekii has been recorded in flying squirrels and their ectoparasites in several states, especially eastern and southern states. Peak seroprevalence (about 90%) in the squirrels occurs during late autumn and winter, when fleas and sucldng lice are also most abundant on these hosts. Although several ectoparasites can imbibe R. prowazekii when feeding on infected flying squirrels, only the sucldng louse Neohaematopinus sciuropteri (Fig. 4.7C) is known to maintain the infection and transmit the pathogen to uninfected squirrels. Several cases of human infection have been documented in which the patients recalled having contact with flying squirrels, especially during the winter months when these rodents commonly occupy attics of houses. To distinguish this form of the disease from classic and recrudescent typhus, it is called sporadic epidemic typhus or sylvatic epidemic typhus. Many details, such as the prevalence and mode of human infection, remain unresolved. Because the louse N. sciuropteri does not feed on humans, it is speculated that human disease occurs when infectious, aerosolized particles of infected louse feces are inhaled from attics or other sites occupied by infected flying squirrels. Except for flying squirrels in North America, humans are the only proven reservoirs of R. prowazekii. Widespread reports published in the 1950s to 1970s that various species of ticks and livestock animals harbored R. prowazekii have since been disproved. Historically, epidemic typhus has been the most widespread and devastating of the louse-borne diseases. Zinsser (1935) and Snyder (1966) have documented the history of this disease and highlighted how major epidemics have influenced human history. For example, the great outbreak of disease at Athens in 430 BC, which significantly influenced the course of Greek history, appears to have been caused by epidemic typhus. Napoleon’s vast army of 1812 was defeated more by epidemic typhus than by opposing Russian forces. Soon thereafter (ca. 1816- 1819), 700,000 cases of epidemic typhus occurred in Ireland. Combined with the potato famine of that period, this encouraged many people to emigrate to North America; some of these people carried infected lice or latent infections with them. During World War II, several military operations in North Africa and the Mediterranean region were hampered by outbreaks of epidemic typhus. One epidemic in Naples in 1943 resuited in over 1400 cases and 200 deaths. This outbreak is particularly noteworthy because it was the first epidemic of the disease to be interrupted by human intervention through widespread application of the insecticide dichlorodiphenyltrichloroethane (DDT) to louseinfested persons. Today, epidemic typhus is much less of a health threat than it once was. This is largely because few people, especially in developed countries, are currently infested by body lice. Higher sanitary standards, less overcrowding, regular laundering and frequent changes of clothes, effective pesticides, and medical advances have contributed to the demise of this disease. Nevertheless, epidemic typhus has the potential to re-emerge. This is evidenced by the largest outbreak of epidemic typhus since World War II that affected about half a million people living in refugee camps in Burundi in 1997-1998. Similarly, more than 5600 cases were recorded in China during 1999. Additional information about epidemic typhus is provided by the Pan American Health Organization/World Health Organization (1973), McDade (1987), and Azad (1988).

LOUSE-BORNE RELAPSING FEVER

Also known as epidemic relapsing fever, this disease is caused by the spirochete bacterium Borrelia recurrentis. This pathogen is transmitted to humans by the human body louse, as first demonstrated by Sergent and Foley in 1910. Clinical symptoms include the sudden onset of fever, headache, muscle ache, anorexia, dizziness, nausea, coughing, and vomiting. Thrombocytopenia (a decrease in blood platelets) also can occur and cause bleeding, which may initially be confused for a symptom of a hemorrhagic fever. Episodes of fever last 2-12 days (average, 4 days), typically followed by periods of 2-8 days (average, 4 days) without fever, with two to five relapses being usual. As the disease progresses, the liver and spleen enlarge rapidly, leading to abdominal discomfort and labored, painful breathing as the lungs and diaphragm are compressed. At this stage, most patients remain quietly prostrate with a glazed expression, often shivering and taking shallow breaths. Mortality rates for untreated outbreaks range from 5 to 40%. Antibiotic treatment is with penicillin or tetracycline. Humans are the sole known reservoir of B. recurrentis. Body lice become infected when they feed on an infected person with circulating spirochetes. Most of the spirochetes perish when they reach the louse gut, but a few survive to penetrate the gut wall, where they multiply to massive populations in the louse hemolymph, nerves, and muscle tissue. Spirochetes do not invade the salivary glands or ovarian tissues and are not voided in louse feces. Therefore, transmission to humans occurs only when infected lice are crushed during scratching, which allows the spirochetes in infectious hemolymph to invade the body through abrasions and other skin lesions. However, B. recurrentisis also capable of penetrating intact skin. As with R. prowazekii infections, body lice are killed as a result of infection with B. recurrentis. An intriguing history of human epidemics of louseborne relapsing fever is provided by Bryceson et al. (1970). Hippocrates described an epidemic of ” caucus,” or “ardent fever,” in Thasos, Greece, which can clearly be identified by its clinical symptoms as this malady. During 1727-1729, an outbreak in England killed all inhabitants of many villages. During the present century, an epidemic that spread from eastern Europe into Russia during 1919-1923 resulted in 13 million cases and 5 million deaths. Millions also were infected during an epidemic that swept across North Africa in the 1920s. Several major epidemics subsequently have occurred in Africa, with up to 100,000 fatalities being recorded for some of them. During and immediately after World War II, more than a million persons were infected in Europe alone. The only current epidemic of louse-borne relapsing fever is in Ethiopia, where 1000-5000 cases are reported annually, accounting for ca. 95% of the world’s recorded infections. Other smaller loci occur intermittently in other regions, such as Burundi, Rwanda, Sudan, Uganda, People’s Republic of China, the Balkans, Central America, and the Peruvian Andes. Resurgence of this disease under conditions of warfare or famine is an ominous possibility. Additional information on louseborne relapsing fever is provided by Bryceson et al. (1970).

TRENCH FEVER

Also known as five-day fever and wolhynia, trench fever is caused by infection with the bacterium Bartonella (formerly Rochalimaea) quintana. Like the two preceding diseases, the agent is transmitted by the human body louse. Human infections range from asymptomatic through mild to severe, although fatal cases are rare. Clinical symptoms are nonspecific and include headache, muscle aches, fever, and nausea. The disease can be cyclic, with several relapses often occurring. Previously infected persons often maintain a cryptic infection which can cause relapses years later, with the potential for spread to other persons if they are infested with body lice. Effective antibiotic treatment of patients involves administering drugs such as doxycycline or tetracycline. Lice become infected with B. quintana after feeding on the blood of an infected person. The pathogen multiplies in the lumen of the louse midgut and in the cuticular margins of the midgut epithelial cells. Viable rickettsiae are voided in louse feces, and transmission to humans occurs by the posterior-station route when louse bites are scratched. B. quintana can remain infective in dried louse feces for several months, contributing to aerosol transmission as an alternative route of transmission. Transovarial transmission does not occur in the louse vector. Infection is not detrimental to lice and does not affect their longevity. Trench fever was first recognized as a clinical entity in 1916 as an infection of European troops engaging in trench warfare during World War I. At that time, more than 200,000 cases were recorded in British troops alone. Between the two world wars, trench fever declined in importance but re-emerged in epidemic proportions in troops stationed in Europe during World War II. Because of the presence of asymptomatic human infections, the current distribution of trench fever is difficult to determine. However, since World War II, infections have been recorded in several European and African nations, Japan, the People’s Republic of China, Mexico, Bolivia, and Canada. Until recently, B. quintana was considered to be transmitted solely by body lice. However, several homeless or immunocompromised people, including HIV-positive individuals, particularly in North America and Europe, have presented with opportunistic B. quintana infections. This is manifested not as trench fever but as vascular tissue lesions, liver pathology, chronically swollen lymph nodes, and inflammation of the lining of the heart. Because some of these patients were not infested by body lice, an alternate mode of pathogen transmission may have been involved.

Pathogens Transmitted by Lice

HUMAN LICE AS INTERMEDIATE HOSTS OF TAPEWORMS

Occasionally humans become infested with the doublepored tapeworm (Dipylidium caninum). Although carnivores are the normal definitive hosts for this parasite, humans can be infested if they accidentally ingest dog biting lice (T. canis), which serve as intermediate hosts. Although this would appear to be an unlikely event, infants, especially babies playing on carpets or other areas frequented by a family dog, may touch an infested louse with sticky fingers which may then be put into their mouth, thus initiating an infestation.

VETERINARY IMPORTANCE

Several chewing lice and sucking lice parasitize domestic animals (Tables I, II). Although louse populations are usually low on these hosts, lice can sometimes multiply to extremely high numbers, particularly on very young, old, or sick animals. Often this is because hosts are unable to effectively groom themselves or they are immunocompromised. Except for the possibility of pathogen transmission, small numbers of lice typically cause little harm to the host. However, large numbers of lice can be debilitating by causing anemia, dermatitis, allergic responses, hair or feather loss, and other disorders. Lice also induce intensive host grooming, which can lead to the formation of hair balls in the stomach, especially in cats and canes. A few pathogens are lmown to be transmitted to domestic animals by lice (Table III). The most important of these are the viral agent of swinepox and the bacterial agents of murine haemobartonellosis and murine eperythrozoonosis, all of which are widely distributed. In addition to those listed in Table III, several pathogens have been detected in various species of lice, but there is no current evidence that lice are vectors of these organisms.

LICE OF LIVESTOCK

Although louse populations of a few hundred individuals commonly occur on healthy livestock, sometimes these numbers can reach into the thousands or, rarely, to more than a million per animal. It is under thc latter conditions that detrimental effects to the host occur. These include restlessness, pruritus, anemia, low weight gain, low milk yield, dermatitis, hide or fleece damagc, skin crusting or scabbing, and lameness. Large louse populations on domestic stock typically develop on juvenile, senile, sick, nutritionally deprived, or immunocompromised hosts.

Sucking louse infestations of cattle, such as those caused by the shortnosed cattle louse (Haematopinus eurysternus), the cattle tail louse (H. quadripertusus), and the longnosed cattle louse ( Linognathus vituli) (Fig. 4.7H), can cause serious damage to the host. This can be manifested as frequent rubbing of infested areas, hair loss, scab formation, slow recovery from disease or trauma, and low weight gain. Younger animals are typically more severely affected than older cattle. Mixed infestations of both chewing and sucking lice on cattle, or of both lice and nematodes, can affect weight gains more severely than single infestations. In single or mixed infestations, weight gains are typically lower in stressed cattle and those on low-nutrition diets. Sometimes, cattle sucking lice cause severe anemia, abortions, or even death. Irritation can be caused by small numbers of lice in sensitive cattle and usually results in frequent rubbing and subsequent hide damage. This rubbing also damages livestock facilities. Severely infested cattle often have patches of bare skin and a greasy appearance which results from crushing lice and their feces during rubbing. Under laboratory or confined conditions, at least three pathogens can be transmitted by cattle sucking lice, i.e., the causative agents of bovine anaplasmosis, dermatomycosis (ringworm) (Table III), and, rarely, theileriosis. The importance of cattie lice in transmitting any of these pathogens in nature is unknown but presumed to be low. Lice of horses and other equids typically do not greatly debilitate their hosts except when they are present in large numbers. Pruritus, hair loss, and coat deterioration may occur in severely infested animals. Horses with severe louse infestations are nervous and irritable; they typically rub against objects, kicking and stamping. Hair can be rubbed from the neck, shoulders, flanks, and tail base, resulting in an unkempt appearance that may affect the value of the horse. No pathogens are known to be transmitted by equid lice. Hog lice can imbibe significant volumes of blood from hogs, especially piglets, which often have larger infestations than adult pigs. Hog-louse feeding sites often cause intense irritation, leading their hosts to rub vigorously against objects, which can result in hair loss and reddened or crusty skin lesions. Haematopinus suis is a vector of the virus that causes swinepox (Table III), a serious and potentially fatal disease characterized by large pockmark lesions, mainly on the belly of infected animals. Some studies have implicated this louse as a vector of Eperythrozoon suis and E. parvum, causative agents of swine eperythrozoonosis, and of African swine fevervirus. However, transmission of these pathogens by lice appears to be rare, if it occurs at all, in nature. All species of lice that parasitize sheep and goats (Tables I and II) can cause debilitation, even when present in relatively small numbers, because of the potential

FIGURE 4.15 Fleece damage (wool slippage) in a sheep, caused by severe infestation with Linognathus africanus (Anoplura). (Courtesy of John E. Lloyd)
FIGURE 4.15 Fleece damage (wool slippage) in a sheep, caused by severe infestation with Linognathus africanus (Anoplura). (Courtesy of John E. Lloyd)

damage which they can cause to fleece and wool (Fig. 4.15). Some sheep develop hypersensitivity to the sheep biting louse (Bovicola ovis) (Fig. 4.16). This louse causes most sheep fleece devaluation worldwide and is the major cause of cockle, an economically disfiguring condition of sheep fleece that is particularly prevalent in New Zealand. Any increase in skin lesions or body rubbing in response to lice generally devalues wool or mohair. Different breeds of sheep and goats exhibit contrasting levels of resistance or tolerance to infestation by lice.

LICE OF CATS AND DOGS

Louse infestations of cats and dogs are most noticeable on sick or senile hosts. Under these conditions, louse populations can increase dramatically. Severe infestations of any of the four species involved usually cause host restlessness, scratching, skin inflammation, a ruffled or matted coat, and hair loss. The dog biting louse ( T. canis) is an intermediate host of the double-pored tapeworm (D. caninum) (Table III). Lice become infected when they ingest viable D. caninum eggs from dried host feces. The tapeworm develops into a cysticercoid stage in the louse, where it remains quiescent unless the louse is ingested by a dog, usually during grooming. In the dog gut, the cysticercoid is liberated and metamorphoses into an adult tapeworm. The dog sucking louse (L. setosus) has been shown to harbor immatures of the filarial nematode Dipetalonema reconditum, which parasitizes dogs, but whether or not these lice are efficient vectors remains unknown.

FIGURE 4.16 Sheep-biting louse (Bovicola ovis), showing prothorax and head with mandibles characteristically grasping a host hair: scanning electron micrograph. (From Price and Graham, 1997)
FIGURE 4.16 Sheep-biting louse (Bovicola ovis), showing prothorax and head with mandibles characteristically grasping a host hair: scanning electron micrograph. (From Price and Graham, 1997)

LICE OF LABORATORY ANIMALS

Some lice that parasitize laboratory animals initiate serious health problems by causing pruritus, skin lesions, scab formation, anemia, and hair loss. Others are vectors of pathogens that can cause severe problems in animal colonies (Table III). The mouse louse (P. serrata) is a vector of the bacterium Eperythrozoon coccoides, which causes murine eperythrozoonosis, a potentially lethal infection of mice that occurs worldwide. Infection of this blood parasite in mice can either be inapparent or result in severe anemia. Transmission of this pathogen in louse-infested mouse colonies is usually rapid. The spined rat louse (P. spinulosa) is a vector of the bacterium Haemobartonella muris, which causes murine haemobartonellosis (Table III), another potentially fatal blood infection that can cause severe anemia in laboratory rats. Laboratory and wild guinea pigs are parasitized by two species of chewing lice, the slender guineapig louse Gliricola porcelli) and the ovalguineapig louse ( Gyropus ovalis). Small numbers of these lice cause no noticeable harm, whereas large populations can cause host unthriftihess, scratching (especially behind the ears), hair loss, and a ruffled coat. Large infestations of the rabbit louse ( Haemodipsus ventricosis) can cause severe itching and scratching, which results in the host rubbing against its cage, often resulting in hair loss. Young rabbits are more adversely affected than are adults and may experience retarded growth as a consequence of infestation by H. ventricosis. The rabbit louse is also a vector of the causative agent of tularemia among wild rabbit populations (Table III).

LICE OF POULTRY AND OTHER BIRDS

Although louse populations may be very large on domestic fowl, including domestic chickens, turkeys, guinea fowl, pea fowl, and pheasants, no pathogens are known to be transmitted by these lice. Large populations often occur on birds with damaged beaks whose grooming ability is significantly impaired. The chicken body louse (Menacanthus stramineus) (Fig. 4.14) often causes significant skin irritation and reddening through its persistent feeding. Occasionally the skin or soft quills bleed from their gnawing and scraping action, with the lice readily imbibing the resultant blood. The shaft louse (Menopon gallinae) also causes significant losses to the poultry industry, including deaths of young birds with heavy infestations. Large infestations of chicken body lice, shaft lice, and other poultry lice may be injurious to the host by causing feather loss, lameness, low weight gains, inferior laying capacity, or even death. The vast majority of chewing lice are parasites of wild or peridomestic birds. Several of these lice are suspected vectors of avian pathogens. Some chewing lice of aquatic birds, including geese and swans, are vectors offilarial nematodes (Table III). Pet parrots, parakeets, budgerigars, and other birds also are subject to infestation by chewing lice, which is usually noticed only by the associated host scratching and by ruffled or lost feathers. Large populations of these lice can debilitate their hosts. Ranch birds, such as ostriches, emus, and rheas, are prone to similar adverse effects caused by their associated chewing lice.

PREVENTION AND CONTROL

Several techniques have been used in attempts to rid humans and animals of lice and louse-borne diseases. Preventing physical contact between lousy persons or animals and the items they contact, as well as various chemical, hormonal, and biological control mechanisms, comprise the current arsenal of techniques. Chemicals used to kill lice are called pediculicides. Clothes of persons with body lice should be changed frequently, preferably daily, and washed in very hot, soapy water to kill lice and nits. Washing associated bed linen in this manner is also advisable. Infested people should also receive a concurrent whole-body treatment with a pediculicide. Overcrowded and unsanitary conditions should be avoided whenever possible during outbreaks of human body lice and louse-borne diseases because it is under these situations that both can thrive. Crab lice can often be avoided by refraining from multiple sexual partners and changing or laundering bed linen slept on by infested persons. Pediculicides should be applied to the pubic area and to any other infested body regions. To reduce the spread of head lice, the sharing of combs, hats, earphones, and blankets, especially by children, should be discouraged. Often, parents of children with head lice are notified to keep youngsters away from school or other gatherings until the infestation has been eliminated. If the parents are also infested, this can further involve ridding the entire family of lice to prevent reinfestations. Various pediculicidal shampoos, lotions, and gels are widely available for controlling head lice. These treatments typically kill all nymphal and adult lice, but only a small proportion of viable louse eggs. Therefore, treatments should be repeated at weekly intervals for 2-4 weeks in order to kill any recently hatched lice. Hatched or dead nits which remain glued to hair may be unsightly or embarrassing, and these can be removed with a fine-toothed louse comb. Louse combs have been used, in various forms, since antiquity to remove head lice (Mumcuoglu 1996). A wide range of pediculicides is commercially available. Although its use is now banned in many developed countries, the organochlorine DDT is widely used, especially in less developed countries, for controlling human and animal lice. Several alternative pediculicides, such as lindane, chlorpyrifos, diazinon, malathion, permethrin, or pyrethrins, are currently used throughout the world. Pediculicides can be used in powders, fogs, or sprays to treat furniture or premises for lice. Several general parasiticides show promise as pediculicides. Avermectins such as abamectin, doramectin, and ivermectin can kill human body lice and livestock lice. Prescribed doses of these compounds can be administered orally, by injection, or as topical applications of powders, dusts, and pour-ons. However, many of these compounds have not yet been approved for use on humans. The development of novel control agents for lice is a constant process because resistance to various pediculicides has developed in lice in many parts of the world (Burgess 1995, Mumcuoglu 1996).

Lice of livestock can be controlled by both husbandry practices and chemical intervention. Providing a high-energy diet, especially to cattle, can be an effective louse control strategy. If possible, it is important to keep animals in uncrowded conditions and to spot-treat or quarantine any infested individuals until they have been successfully deloused. Various formulations and applications of pediculicides are typically used to control lice on livestock. Insecticidal dusts, powders, sprays, dips, ear tags, tail tags, resin strips, gut boluses, collars, pour-ons, lotions, and injections are widely used products. Infested animals should be treated twice weekly for 2-4 weeks. Insecticidal dust bags or back rubbers can be used as selfdosing rubbing stations for cattle and other livestock. Because louse populations on livestock are typically greater during the winter months, pediculicides are usually best applied to them in the late fall. Fall systemic treatments of cattle for both lice and bots are often administered. Shearing wool from sheep removes up to 80% of the lice present on infested animals. Pets, laboratory animals, and poultry can be treated for lice in several ways. Pets such as dogs and cats can be dipped or bathed with a pediculicidal lotion or shampoo. Various oral or topically applied insecticides used for controlling fleas on pets also are efficacious against lice. Similarly, flea combs also remove lice from pets. Poultry and laboratory animals can be treated with pediculicidal dusts or sprays. Although host treatment is most efficacious, bedding materials and cages can also be treated. Insecticidal feed additives are also available. Insecticideimpregnated resin strips can be added to cages of poultry or laboratory animals to control lice. The bacterium Bacillus thuringiensis and the nematodes Steinernema carpocapsae and S. glaseri, which are effective biological control agents against numerous arthropods, can also be used to kill livestock lice. Some juvenile hormone analogs and insect growth regulators such as diflubenzuron have similarly shown promise as pediculicides. With respect to louse-borne diseases, vaccines have been developed only against epidemic typhus, and none is completely safe or currently approved for widespread use. The live attenuated E-strain vaccine has been administered to humans, particularly in certain African nations, in attempts to quell epidemic typhus outbreaks. However, this vaccine actually caused disease in some patients and did not always prevent subsequent infection.

Cockroaches (Blattaria)

Cockroaches are among the oldest and most primitive of insects. They evolved about 350 million years ago during the Silurian Period, diverging together with the manrids from an ancestral stock that also gave rise to termites (Boudreaux 1979). Cockroaches are recognized as the order Blattaria. Although the majority of species are feral and not directly associated with people, a few species have evolved in proximity to human habitations, where they have adapted to indoor environments. Their omnivorous feeding behavior, facilitated by their unspecialized chewing mouthparts, has contributed to a close physical relationship between cockroach populations and humans, with resultant chronic exposure of humans to these pests. The presence of some species in the home (e.g., German and brownbanded cockroaches) often is an indicator of poor sanitation or substandard housekeeping.

Although they are primarily nuisance pests, their presence can have important health implications. Cockroaches are generalists that feed on virtually any organic substance grown, manufactured, stored, excreted, or discarded by humans. Consequently, food supplies are at risk of contamination by pathogens associated with cockroaches. Because species that infest structures typically have high reproductive rates, humans commonly are exposed to high levels of potentially allergenic proteins associated with cockroaches, which can lead to significant respiratory ailments. Cockroaches also can serve as intermediate hosts of parasites that debilitate domestic animals.

TAXONOMY

There are about 4000 species of cockroaches worldwide. About 70 species occur in the United States, 24 of which have been introduced from other parts of the world. According to Atldnson et al. (1991), 17 of these species are pests of varying degrees. There are five cockroach families, three of which include most of the pest species: Blattidae, Blattellidae, and Blaberidae. Species in the Cryptocercidae are unusual in that they have gut symbionts similar to those found in termites, and they live in family groups in decaying logs. Members of the Polyphagidae include those dwelling in arid regions, where they are capable of moving rapidly through sand. Species in these two families are rarely pests. The family Blatfidae includes relatively large cockroaches that are the most common peridomestic pests throughout much of the world. Blattellid cockroaches range in length from less than 25 mm (e.g., Supella and Blattella) to 35-40 mm (e.g., Periplaneta and Parcoblatta spp.). Parcoblatta species are feral, occasionally invading homes but seldom reproducing indoors. Blaberid cockroaches range greatly in size and include some of the more unusual species, such as the Cuban cockroach, which is green as an adult, and the Surinam cockroach, which is parthenogenetic in North America. Nearly all of the blaberids that occur in the United States are restricted to subtropical regions and have minor medical or veterinary significance. Taxonomic keys for adults are provided by McKittrick (1964), Cornwell (1968), Roth (1985), and Heifer (1987). A pictorial key for identifying the egg cases of common cockroaches is provided by Scott and Borom (1964).

MORPHOLOGY

Cockroaches have retained their basic ancestral form. The Blattaria are distinguished from other insect orders by morphological characters associated with wing size and venation, biting/chewing mouthparts, and prominent cerci. They differ from other orthopteroid insects by having hind femora which are not enlarged, cerci typically with eight or more segments, a body that is dorsoventrally flattened and generally ovoid, and a head that is largely concealed from above by a relatively large pronotum.

A common indicator of cockroach infestations is their egg cases, or oothecae (singular ootheca), purse-shaped capsules that typically contain 5-40 embryos (Fig. 3.1). Coloration ranges from light brown to chestnut brown, depending on the degree of sclerotization. A keel that runs the anterior length of the ootheca permits transport of water and air to the developing embryos. Each embryo is contained in a separate compartment that may or may not be obvious externally. In some species (e.g., German and brownbanded cockroaches) lateral, anterior-to-posterior indentations denote the individual developing embryos. Others have only weak lateral indentations (e.g., brown and smokybrown cockroaches), and still others have no lateral indentations but differ in their symmetry (e.g., Oriental, American, and Australian cockroaches).

The mouthparts of cockroach nymphs and adults are characterized by strongly toothed mandibles for biting and chewing. Maxillary and labial palps are well developed, with five and three segments, respectively. Antennae are long and whiplike, originate directly below the middle of the compound eyes, and consist of numerous small segments. The arrangement of three ocelli near the

Cockroach oothecae (egg cases). A, Australian cockroach (Periplaneta australasiae); B, Brown cockroach (P. brunnea); C, Smokybrown cockroach (P. fuliginosa); D, Oriental cockroach (Blatta orientalis); E, American cockroach (P. americana); F, Brownbanded cockroach (Supella longipalpa); G, German cockroach (Blattella germanica). (Courtesy of the US Public Health Service)
FIGURE 3.1 Cockroach oothecae (egg cases). A, Australian cockroach (Periplaneta australasiae); B, Brown cockroach (P. brunnea); C, Smokybrown cockroach (P. fuliginosa); D, Oriental cockroach (Blatta orientalis); E, American cockroach (P. americana); F, Brownbanded cockroach (Supella longipalpa); G, German cockroach (Blattella germanica). (Courtesy of the US Public Health Service)

antennal sockets is variable: they are well developed in winged species (macropterous) but rudimentary or lacking in species with reduced wings (brachypter0us) or those lacking wings altogether (apterous).

Adults generally have two pairs of wings that are folded fanwise at rest. The front wings, called tegmina (singular tegmen), are typically hardened and translucent, with well-defined veins. The hind wings are membranous and larger. In some species, such as the wood cockroaches (e.g., Parcoblatta species), females are brachypterous and incapable of flight, whereas males are macropterous. Other species, such as the Florida woods cockroach (Eurycot# floridana), have only vestigial wing buds as adult males and females. In cockroaches, all three pairs of legs are well developed, with large coxae and slender, long segments that aid in the rapid running that is characteristic of these insects. Each femur has two longitudinal keels that typically are armed with spines. The tibiae are often heavily spined and are used for defense against predators. Each tarsus consists of five segments with a pair of claws and may bear a padlike arolium that aids in walking on smooth surfaces. Ventral pads, or pulvilli, are present on tarsomeres 1-4. A pair of caudal cerci have small ventral hairs that are sensitive to vibrations caused by lowfrequency sound and air movement; their stimulation initiates an escape response.

The posterior end of the abdomen of some nymphs and all males bears a pair of styli (singular stylus) between the cerci, arising from the sternum of the ninth abdominal segment. In winged species, the styli may be apparent only when viewed ventrally. The structure of the styli serves to distinguish males from females. Generally the males also can be recognized by their more slender bodies, with laterally tapered and dorsally flattened external genitalia (terminalia). The terminalia of the more robust females are notably broader than in males and bear a conspicuous subgenital plate that is rounded or keel-like when viewed ventrally. Associated with this plate is a relatively large genital chamber (genital pouch) in which the ootheca develops. For a more detailed description of cockroach genitalia, see McI~ttrick (1964) or Cornwell (1968). Nymphal stages are similar in appearance to adults, but they lack wings, have incompletely developed genitalia, and may vary markedly in color from the adult.

LIFE HISTORY

Cockroaches are paurometabolous insects. The immature cockroaches generally are similar in appearance to the adults except for their undeveloped sexual organs and lack of fully developed wings (Fig. 3.2). Reproduction in cockroaches is typically sexual, although parthenogenesis is reported in a few species. Comparative life history data for some of the more common cockroach pests are provided in Table I.

In cockroaches, embryogenesis and oviposition occur in one of three ways. Most species are oviparous, including

Developmental stages of cockroaches, represented by Periplaneta brunnea. Left to right: first, second, third, and fourth nymphal instars; adult female, adult male. (Courtesy of Daniel R. Suiter)
FIGURE 3.2 Developmental stages of cockroaches, represented by Periplaneta brunnea. Left to right: first, second, third, and fourth nymphal instars; adult female, adult male. (Courtesy of Daniel R. Suiter)

all Periplaneta species and the Oriental and brownbanded cockroaches. Eggs of oviparous species are protected inside a thick-walled, impermeable ootheca which is deposited soon after it is formed. Embryonic development occurs external to the female. The German cockroach is oviparous, but the female carries the ootheca protruding from the genital chamber until just hours before hatching occurs. The ootheca is softer than in Periplaneta species, allowing uptake of water and nutrients from the genital pouch. A few cockroaches, such as Blaberus species and the Surinam cockroach, are pseudo-ovoviviparous, in that females produce an ootheca which is extruded, rotated, and then retracted into the genital pouch. The eggs are incubated internally until hatching. The only known pseudo-viviparous species is Diploptera punctata, a pest species in Hawaii; the embryos hatch while still in the genital pouch. Embryogenesis takes 1-8 weeks, depending on the species.

The number of nymphal instars varies from 5 to 13, depending on the species, nutritional sources, and microclimate. Development of pestiferous species through the nymphal stadia requires from 6-7 weeks for German cockroaches to well over a year for Periplaneta species and other larger cockroaches. Typically, the nymphs exhibit strong aggregation tendencies, governed largely by aggregation pheromones. These pheromones act as locomotory inhibitors; when cockroaches perceive the pheromone they become relatively stationary. Studies of various species have shown that development to the adult stage is quicker when nymphs are reared in groups rather

I Life Histories of Selected Common Species of Cockroaches, Showing the High Degree of Variability Within Species Due to Environmental Temperatures and Nutritional Availability

 

than in isolation. However, aggregation does have a biological cost; those reared in groups typically are smaller in size, and cannibalism may occur. Longevity of cockroaches varies from several weeks to over a year.

BEHAVIOR AND ECOLOGY

Mating in cockroaches generally is preceded by courtship behavior facilitated by sex pheromones. In some species a blend of volatile compounds is produced by virgin females to attract and orient males (e.g., Periplaneta species and the brownbanded cockroach). In the German cockroach, the sex pheromone is a blend of nonvolatile and volatile cuticular components that elicits courtship by males following palpation of the female’s integument by the male’s antennae. Once courtship is initiated in the male, he turns away from the female and raises his wings to expose dorsal tergalglands; the female feeds on pheromones from these glands as the male grasps her genitalia with his pair of caudal claspers. Most species copulate in an end-to-end position. During the hour or so that follows, a spermatophore is formed and passed from the male into the genital chamber of the female. Only about 20% of females mate again after the first gonotrophic cycle.

Cockroaches can be categorized ecologically as domestic, peridomestic, or feral. Domestic species live almost exclusively indoors and are largely dependent on humans for resources (food, water, and harborage) for survival. They rarely are able to maintain themselves outdoors. Although this group contains the smallest number of species, it presents the greatest concern to human health. Domestic species include the German and brownbanded cockroaches. Peridomestic species are those which survive in or around human habitation. Although they do not require humans for their survival, they are adept at exploiting the amenities of civilization. This group is represented by American, Australian, brown, and smokybrown cockroaches (all Periplaneta species), the oriental cockroach, and the Florida woods cockroach. Feral species are those in which survival is independent of humans. This group includes more than 95% of all species in the world. Only a few occur indoors as occasional and inadvertent invaders that typically do not survive in a domestic environment. They are of little or no medical importance.

Cockroach behavior and survival are strongly influenced by their need for food, water, and safe harborage from potential predators and detrimental microclimates. They are omnivorous and will consume virtually any organic matter, including fresh and processed foods, stored products, and even book bindings and pastes on stamps and wallpaper when more typical foodstuffs are not available. Cockroaches have the same general problems with water balance as do other terrestrial arthropods. Their relatively small size results in a high surface area to volume ratio and a high risk of losing water through respiration, oral and anal routes, or the cuticle. Temperature, air flow, relative humidity, and availability of liquid water greatly affect water regulation.

As a result of these physiological considerations, physical constraints of the environment usually determine habitat preferences of cockroaches in and around structures. Oriental and American cockroaches, for example, require high moisture and occur in damp terrestrial environments such as septic tanks and municipal sewer systems. Brown, smokybrown, and Florida woods cockroaches occur in a wider range of habitats associated with trees, wood and leaf piles, wall voids, and foundation blocks of buildings. Brownbanded cockroaches are more tolerant of drier conditions and commonly occur in kitchens, pantries, and bedrooms. German cockroaches occupy harborages near food and water. Consequently, they are found primarily in kitchens and pantries, and secondarily in bathrooms, when their populations are high. In mixed populations of German and brownbanded cockroaches, the German cockroach tends to outcompete the brownbanded cockroach within 9 months.

Cockroaches are adept crawlers and are capable of rapid movement even across windows and ceilings. Flight ability varies with species. Some are incapable of flight except for crude, downward gliding used as an escape behavior. Others are weak fliers, occasionally seen flying indoors when disturbed. Still others are relatively strong fliers that are particularly active at sunset, when they may be attracted indoors by lights and brightly lit surfaces. Attraction to light is especially common in the Asian, Surinam, and Cuban cockroaches and in many of the wood cockroaches (Parc0blatta species).

Pestiferous cockroaches that occur indoors are typically nocturnal and tend to avoid lighted areas. This enables them to increase their numbers and become established in structures before human occupants even become aware of their presence.

COMMON COCKROACH SPECIES

The following 11 species of cockroaches are commonly encountered by homeowners in the United States and are the ones most frequently brought to the attention of medical entomologists.

Oriental cockroach (Blatta orientalis)

This peridomestic cockroach (Fig. 3.3) is believed to have originated in northern Africa and from there spread to Europe and western Asia, South America, and North America. It is a relatively lethargic species that prefers cooler temperatures than does the German cockroach and is primarily a concern in temperate regions of the world. Adults are black and 25-33 mm long. Males are winged but do not fly, and females are

Oriental cockroach (Blattella orientalis), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.3 Oriental cockroach (Blattella orientalis), female. (Courtesy of the University of Florida/IFAS)
American cockroach (Periplaneta americana), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.4 American cockroach (Periplaneta americana), female. (Courtesy of the University of Florida/IFAS)

brachypterous. Their tarsi lack aroliar pads, precluding this cockroach from climbing on smooth vertical surfaces. Oothecae are 8-10mm long, each typically containing 16 eggs. Also commonly lmown as waterbug, this species is usually associated with damp or wet conditions, such as those found in decaying wood, heavy ground cover (e.g., ivy) , water meter boxes, and the lower levels of structures. It infests garbage chutes of apartment complexes, sometimes reaching upper floors. Development is slow compared to that of most other species, requiring about a year depending on temperature conditions. Adults may live for many months. Mobility is fairly restricted, malting control easier than for most other species. This species is rarely seen during the daytime.

American cockroach (Periplaneta americana)

The American cockroach (Fig. 3.4) is a large species with adults 34-53 mm in length. It is reddish brown, with substantial variation in light and dark patterns on the pronotum. Adults are winged and capable of flight. Nymphs typically complete development in 13- 14months while undergoing 13molts. Adults live an average of 15 months, but longevity may exceed 2 years. Females drop or glue their oothecae (8 mm long) to substrates within a few hours or days of formation. Each ootheca has 12-16 embryos. A female generally produces 6-14 egg cases during her life (mean of 9).

The American cockroach is perhaps the most cosmopolitan peridomestic pest species. Together with other closely related Periplaneta species, P. americana is believed to have spread from tropical Africa to North America and the Caribbean on ships engaged in slave trading. Today this species infests most of the lower latitudes of both hemispheres and extends significantly into the more temperate regions of the world.

The habitats of this species are quite variable. American cockroaches infest landfills, municipal sewage systems, storm drainage systems, septic tanks, crawl spaces beneath buildings, attics, tree holes, canopies of palm trees, voids in walls, ships, electronic equipment, caves, and mines. Studies conducted in Arizona indicated movement by a number of individuals several hundred meters through sewer systems and into neighboring homes. This species often can be seen at night on roofs and in air stacks or vents of sewage systems, through which they enter homes and commercial buildings. Entrance also is gained to homes through laundry vent pipes and unscreened or unfiltered attic ventilation systems. This cockroach is known to move from crawl spaces of hospitals via pipe chases into operating theaters, patients’ rooms, storage facilities, and food preparation areas. Consequently, the potential of this cockroach for disseminating pathogenic microorganisms can be a significant concern for health care personnel.

Australian cockroach (Periplaneta australasiae)

Adult body coloration is similar to that of the American cockroach, but with paler lateral markings on the upper edges of the tegmina (Fig. 3.5). The pronotum is tinged with similar coloration. Adults are slightly smaller than American cockroaches, measuring 32- 35 mm in length. Females mature in about 1 year and typically live for another 4-6 months. A female can produce 20-30 oothecae during her lifetime; the ootheca is about 11 mm long and contains about 24embryos. Embryonic development requires about 40 days. Nymphs are strikingly mottled, distinguishing them from nymphs of other Periplaneta species.

This peridomestic species requires somewhat warmer temperatures than the American cockroach and does not occur in temperate areas other than in greenhouses and

Australian cockroach (Periplaneta australasiae), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.5 Australian cockroach (Periplaneta australasiae), female. (Courtesy of the University of Florida/IFAS)
Brown cockroach (Periplaneta brunnea), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.6 Brown cockroach (Periplaneta brunnea), female. (Courtesy of the University of Florida/IFAS)

other pseudotropical environs. In the United States, outdoor populations are well established in Florida and along the coastal areas of Louisiana, Mississippi, Alabama, and Georgia. It commonly is found in environments similar to those inhabited by the smokybrown cockroach. In situations where both species occur (e.g., tree holes, attics), the Australian cockroach tends to displace the smokybrown. It can be a serious pest in greenhouses and other tropical environments in more temperate latitudes, where it can cause feeding damage to plants, notably seedlings.

Brown cockroach (Periplaneta brunnea)

The brown cockroach (Fig. 3.6) is smaller than the American cockroach (33-38 mm), and its pronotal markings are more muted. The most apparent diagnostic characteristic for separating these two species is the shape of the last segment of the cercus; in the brown cockroach, the length is about equal to the width, whereas in the American cockroach the length is about 3 times the width. The ootheca of the brown cockroach usually is larger (7-13 vs 8 ram) and contains more embryos (24 vs 16). The brown cockroach affixes its oothecae to substrates using salivary secretions. They give the ootheca a grayish hue not typical of other Periplaneta species that attach their oothecae with salivary secretions. This species is more subtropical than the American cockroach, occurring throughout the southeastern United States, where it infests homes and outbuildings. It is less frequently associated with sewage than is the American cockroach. Because of its similar appearance to the American cockroach, it is often misidentified and may be more widely distributed than is commonly recognized. In Florida, P. brunnea is commonly found in canopies of palm trees and attics. It also readily infests various natural cavities and those in human-associated structures. The oothecae can be useful in differentiating species infesting buildings. Most

Smokybrown cockroach (Periplaneta fuliginosa), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.7 Smokybrown cockroach (Periplaneta fuliginosa), female. (Courtesy of the University of Florida/IFAS)

cockroach oothecae persist in the environment after the nymphs have emerged and provide a history of infestation.

Smokybrown cockroach (Periplanetafuliginosa)

The smokybrown cockroach (Fig. 3.7) has become a major peridomestic pest throughout the southern United States, including southern California, and extends as far north as the Midwestern states. It can be differentiated from the American cockroach by its slightly smaller size (25-33 ram) and uniform dark coloration. Mthough developmental times are quite variable, individuals mature in about 10 months. Adults may live for more than a year. Females produce several oothecae, which are 10-11 mm in length with 20 embryos, at 11-day intervals.

Primary loci for this peridomestic species in the southeastern United States are tree holes, canopies of palm trees, loose mulches such as pine straw or pine bark, and firewood piles. Within structures, P. futiginosa seeks the ecological equivalent of tree holes–areas characterized as dark, warm, protective, and moist, with little air flow and near food resources. These include the soffits (eves) of underventilated attics, behind wall panels, the interstices of block walls, false ceilings, pantries, and storage areas. From these harborages, individuals forage for food and water, generally returning to the same refugia. Mark-release-recapture studies using baited live traps have shown that the median distance traveled between successive recaptures is less than I m but that some adults may forage at distances of more than 30 m.

Florida woods cockroach (Eurycotisfloridana)

This cockroach is restricted to a relatively small area of the United States along the Gulf of Mexico from

Florida woods cockroach (Eurycotisfloridana), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.8 Florida woods cockroach (Eurycotisfloridana), female. (Courtesy of the University of Florida/IFAS)

eastern Louisiana to southeastern Georgia. It is mentioned here only because of its defensive capabilities. It is a large, dark-reddish brown to black cockroach (Fig. 3.8), 30-40 mm long. Although small wing pads are evident, adults are apterous and are relatively slow moving. Oothecae are 13-16 mm long and contain about 22 embryos. E. floridana occurs in firewood piles, mulches, tree holes, attics, wall voids, and outbuildings. Last-instar nymphs and adults, if alarmed, can spray a noxious mix of aliphatic compounds that are both odoriferous and caustic. If this is sprayed into the eyes or onto soft tissues, a temporary burning sensation is experienced. Domestic dogs and cats quicldy learn to avoid this species. Among its common names are the Florida cockroach, the Florida woods roach, the Florida stinkroach, and palmettobug. The last term also is commonly used for other Pcriplaneta species.

Brownbanded cockroach (Supella longipalpa)

Like the German cockroach, this domestic species probably originated in tropical Africa, where it occurs both indoors and outdoors. In North America and Europe it is confined almost exclusively to indoor environments of heated structures. In warm climates, infestations occur particularly in apartments without air conditioning and in business establishments with relatively high ambient temperatures, such as pet stores and animal-care facilities. Adults are similar in size to the those of the German cockroach (13-14.5 mm long) but lack pronotal stripes. Adults have two dark bands of horizontal stripes on the wings (Fig. 3.9), whereas nymphs have two prominent bands running across the mesonotum and first abdominal segment. The brownbanded cockroach derives its name from these bands.

Brownbanded cockroach (Supella longipalpa), female. (Courtesy of the University of Florida/IFAS)
FIGURE 3.9 Brownbanded cockroach (Supella longipalpa), female. (Courtesy of the University of Florida/IFAS)

Populations tend to occur in the nonfood areas of homes, such as bedrooms, living rooms, and closets. Male brownbanded cockroaches occasionally fly and are attracted to lights. Members of this species seek harborage higher within rooms than do German cockroaches. The ootheca is small, only 5 mm long, with an average of 18 embryos and an incubation time of 35-80 days. Females deposit their oothecae by affixing them to furniture, in closets, on or behind picture frames, and in bedding. Transporting S. longipalpa with furniture to new locales is common. Although this species occurs with other cockroaches in homes, the German cockroach often outcompetes it within a few months.

German cockroach (Blattellagermanica)

This cockroach also is known as the steamily in Great Britain. It is believed to have originated in northern or eastern Africa, or Asia, and has spread from there via commerce. The German cockroach is considered to be the most important domestic pest species throughout the developed world. Adults are about 16 mm long, with two dark, longitudinal bands on the pronotum (Fig. 3.10). It requires warm (optimally 30-33°C), moist conditions near adequate food resources. It primarily inhabits kitchens and pantries, with secondary foci in bathrooms, bedrooms, and other living spaces in heavily infested structures. Although this species is nocturnal, like most other cockroaches, some individuals may be seen moving about on walls and in cupboards during the daylight hours where infestations are heavy. Their wing musculature is vestigial, making them unable to fly except for short, gliding, downward movements. B. germanica does not readily move between buildings; however, it does occur in garbage collection containers and outbuildings near heavily infested structures.

German cockroach (Blattella german#a), female. (Courtesy of the University of Florida/IFAS)
HGURE 3.10 German cockroach (Blattella german#a), female. (Courtesy of the University of Florida/IFAS)

The German cockroach has a high reproductive potential. Females produce an ootheca (6-9 ram) containing about 30 embryos within 7-10 days after molting to the adult, or about 2-3 days after mating. The female carries the egg case until a few hours before hatching of the nymphs, preventing access of any oothecal parasitoids or predators. Oothecae are produced at intervals of 20- 25 days, with a female producing 4-8 oothecae during her lifetime. Nymphs complete their development in 7- 12 weeks.

This species is the main cockroach pest in most households and apartment complexes. Control is difficult, in part because of their movement between apartments through plumbing chases in shared or adjacent walls. Researchers studying over 1,000 apartments in Florida concluded that the median number of cockroaches per apartment was >13,000. This high biotic potential makes this species a major nuisance, as well as a pest with implications for human health.

Asian cockroach (Blattella asahinai)

The Asian cockroach is closely related to the German cockroach, from which it is difficult to distinguish morphologically. In fact, Asian and German cockroaches are capable of hybridizing and producing fertile off’- spring, which further complicates their identifications. Techniques have been developed to differentiate these two species and their hybrids based on cuticular hydrocarbons in the waxy layer of the integument.

Despite their morphological similarity, B. asahinai differs from B. germanica in several aspects of its behavior and ecology. It is both a feral and a peridomestic species. Nymphs of the Asian cockroach commonly occur, sometimes in large numbers, in leaf litter and in areas of rich ground cover or well-maintained lawns. Unlike the German cockroach, the adults fly readily and are most active beginning at sunset, when they fly to light-colored walls or brightly lit areas. This behavior can make invasion a nightly occurrence in homes near heavily infested areas. Flight does not occur when temperatures at sunset are below 21°C.

Like those of the German cockroach, Asian cockroach females carry their oothecae until shortly before they are ready to hatch. The ootheca is similar in size and contains the same number of embryos as does that of the German cockroach (38-44). Nymphs are smaller than their B. germanica counterparts and are somewhat paler in appearance. Development from egg to adult requires about 65 days, with females producing up to six oothecae during their life span. Adults also are slightly smaller than those of B. germanica (average of 13 vs 16mm).

The Asian cockroach was first described in 1981 from specimens collected in sugar-cane fields on the Japanese island of Okinawa. When it was first discovered in the United States in 1986, the Asian cockroach was found only locally in three counties in Florida, from Tampa to Lakeland; populations already had become established, with densities as high as 250,000 per hectare. By 1993, this species had spread to at least 30 Florida counties and had infested citrus groves throughout the central part of the state. It feeds on succulent early growth of citrus nursery stock, tassels of sweet corn, strawberries, cabbage, tomatoes, and other agricultural products, although there has been no evidence of significant economic damage.

Infestations of apartments by B. asahinai have become common in central Florida. This cockroach also has become an increasing problem in warehouses, department stores, hotels, fast-food establishments, automobile dealerships, and other businesses with hours of operation that extend beyond dusk.

Surinam cockroach (Pycnoscelus surinamensis)

This species is believed to have originated in the Indo- Malayan region. It commonly occurs in the southeastern United States from North Carolina to Texas. The adults are fairly stout, 18-25 mm in length, with shiny brown wings and a black body (Fig. 3.11). Nymphs characteristically have shiny black anterior abdominal segments, whereas the posterior segments are dull black and roughened. In North America this species is unusual in that it is parthenogenetic, producing only female offspring; elsewhere both males and females are found. The ootheca is 12-15 mm long, is poorly sclerotized, and contains about 26 embryos. Oothecae are retained inside the genital chamber, from which the nymphs emerge in about 35 days. Females produce an average of three oothecae and live about 10 months in the laboratory. This cockroach commonly burrows into compost piles and the thatch of lawns. Transfer

Surinam cockroach (Pycnoscelussurinamensis). (Courtesy of the University of Florida/IFAS)
FIGURE 3.11 Surinam cockroach (Pycnoscelussurinamensis). (Courtesy of the University of Florida/IFAS)

of fresh mulch into the home for potting plants can result in household infestations. Adult females fly and are attracted to light. They are most likely to be noticed by homeowners at night when they fly into brightly lit television screens. This species commonly is transported in commercial mulch to more temperate areas of the United States, where it has been known to infest greenhouses, indoor plantings in shopping malls, and ZOOS.

Cuban cockroach (Panchlora nivea)

This medium-sized cockroach (22-24 mm in length) is unusual in that the adults are pale green. The nymphs are dark brown and are found in leaf litter and decaying wood piles. Adults are strong fliers and are attracted to lights. Panchlora nivea is believed to be native to the Caribbean basin, Mexico, Central America, and northern South America. In the United States it occurs commonly in Florida and coastal Louisiana and Texas. This cockroach often is seen in the evening, resting on windows and glass patio doors, apparently drawn to the brightness of indoor lighting.

PUBLIC HEALTH IMPORTANCE

Cockroaches infesting human dwellings and workplaces represent a more intimate and chronic association than do most other pests of medical/veterinary importance. High populations of any cockroach species may adversely affect human health in several ways. These include contamination of food with their excrement, dissemination of pathogens, induced allergies, psychological stress, and bites. Mthough documentation of bites is limited, there are reports of cockroaches feeding on fingernails, eyelashes, skin calluses of hands and feet, and food residues about the faces of sleeping humans, causing blisters and small wounds (Roth and Willis 1957, 1960). There are other accounts of bites around the mouths of infants in heavily infested homes and even in hospitals. American and Australian cockroaches are the most often implicated species. Bites by the Oriental cockroach have resulted in inflammation of the skin, degeneration of epithelial cells, and subsequent necrosis of the involved tissues.

While many individuals develop a tolerance for cockroach infestations, others may experience psychological stress. The level of stress tends to be proportional to the size of the cockroaches and the magnitude of the infestation. An aversion to cockroaches may be so strong that some people become irrational in their behavior, imagining a severe infestation even when there is none. This illusion of abundant cockroaches has caused some families to move out of their homes. High cockroach populations also produce a characteristic odor that can be unpleasant or even nauseating to some people. Foodstuffs may become contaminated with the excrement of cockroaches, which, on subsequent ingestion, may cause vomiting and diarrhea.

The presence of cockroaches in homes does not necessarily imply poor housekeeping. Peridomestic species such as the American and the Oriental cockroach commonly infest municipal sewage systems or septic tanks and may move into homes through sewage lines. Any of the Periplaneta species may develop high outdoor populations, inducing individuals to seek less crowded environments. At such times, they often enter homes through attic vents, breaches in construction joints, or through crawl spaces. This tends to occur in early fall. While they are active at night the smokybrown cockroach, Asian cockroach, and feral wood roaches (Parcoblatta species) often find their way into even the best-kept homes. Adults frequently alight on doors illuminated by entrance lights, or on window screens of lighted rooms. Entrance is gained once the door is opened or by squeezing past window-screen frames.

Poor housekeeping and unsanitary conditions contribute significantly to cockroach infestations. The German cockroach and, to a lesser degree, the brownbanded cockroach are the principal bane of apartment dwellers. Their survival is enhanced by crowded living quarters, associated clutter, and the accumulated organic debris associated with food preparation. Construction practices used to build apartment complexes (e.g., common wiring ducts, sewage lines, and refuse areas) can contribute to the spread of cockroaches in multiunit dwellings.

Bacteria adhering to tarsus of German cockroach (Blattellagermanica). (From Gazivoda and Fish 1985)
FIGURE 3.12 Bacteria adhering to tarsus of German cockroach (Blattellagermanica). (From Gazivoda and Fish 1985)

PATHOGENIC AGENTS

The significance of cockroaches in public health remains controversial despite the logical assumption that they play a role in transmitting pathogenic agents. Given that cockroaches are so closely associated with humans and poor sanitation, the potential for acquiring and mechanically transmitting disease agents is very real. They are capable of transmitting microorganisms (Fig. 3.12) and other disease agents indirectly by contaminating foods or food preparation surfaces.

Table II lists pathogenic organisms that have been isolated from cockroaches in domestic or peridomestic environments. At least 32 species of bacteria in 16 genera are represented. These include such pathogens as Bacillus subtilis, a causative agent of conjunctivitis; Escherichia coli and 9 strains of Salmonella, causative agents of diarrhea, gastroenteritis, and food poisoning; Salmonella typhi, the causative agent of typhoid; and 4 Proteus species, which commonly infect wounds. These isolations primarily have involved American, German, and Oriental cockroaches. Cockroaches also have been found harboring the eggs of 7 helminth species, at least 17 fungal species, 3 protozoan species, and 2 strains ofpoliomyelitic virus (Brenner et al,. 1987; Koehler et al., 1990, Brenner 1995). Researchers in Costa Rica have shown that Australian, American, and Madeira cockroaches become infected with the protozoan Toxoplasmagondii after eating feces of infected cats. This suggests the possibility of cockroach involvement in the maintenance and dissemination of this parasite, which causes toxoplasmosis in humans, cats, and other animals.

Mthough many pathogens have been recovered from natural populations of cockroaches, this does not necessarily mean that cockroaches serve as their vectors. Isolation of pathogens from cockroaches simply may be

Bacteria Pathogenic to Humans That Have Been Isolated from Field-Collected Cockroaches

indicative of the natural microbial fauna and flora in our domestic environment. Under certain circumstances, however, cockroaches have the potential for serving as secondary vectors of agents that normally are transmitted by other means. Anecdotal accounts associating diseases in humans with the occurrence of cockroaches and microbes lend some credence to the hypothesis that these pests can serve as vectors. Burgess (1982) reported the isolation from German cockroaches of a serotype of S. dysenteriae that was responsible for an outbreak of dysentery in Northern Ireland. Mackerras and Mackerras (1948) isolated S. bovis-morbificans and S. typhimurium from cockroaches captured in a hospital ward where gastroenteritis, attributed to the former organism, was common. In subsequent experimental studies, Salmonella organisms remained viable in the feces of cockroaches for as long as 40 days postinfection (Mackerras and Mackerras 1949). Some of the most compelling circumstantial evidence suggesting that cockroaches may be vectors was noted in a correlation between cases of infectious hepatitis and cockroach control at a housing project during 1956- 1962 in southern California (Tarshis 1962). The study area involved more than 580 apartments and 2800 persons; 95% of the apartments had German cockroaches and a lesser infestation of brownbanded and Oriental cockroaches. After pest control measures were initiated, the incidence of endemic infectious hepatitis decreased for i year. When treatments were discontinued during the following year because the insecticide was offensive to apartment dwellers, the cockroach population increased, accompanied by a corresponding increase in the incidence of hepatitis. Effective control measures were applied for the following 2 years, and cockroach populations and cases of infectious hepatitis dropped dramatically while hepatitis rates remained high in nearby housing projects where no pest control measures were conducted.

INTERMEDIATE HOSTS

Cockroaches can serve as intermediate hosts for animal parasites (Table III). Roth and Willis (1960) published an extensive list of biotic associations between cockroaches and parasitic organisms that potentially infest humans. The eggs of seven species of helminths have been found naturally associated with cockroaches. These include hookworms (Ancylostoma duodenale and Necator americanus), giant human roundworm (Ascaris lumbricoides), other Ascaris species, pinworm (Enterobius vermicularis), tapeworms ( Hymenolepis species), and the whipworm Trichuris trichuria. Development of these helminths in cockroaches has not been observed. These relationships probably represent incidental associations with the omnivorous feeding behavior of cockroaches.

However, cockroaches may serve as potential reservoirs and possible vectors through mechanical transfer in areas where a high incidence of these pathogens in humans is accompanied by substantial cockroach infestations. Human infestations by spirurid nematodes associated with cockroaches are known only for the cattle gullet worm (Gongylonema pulchrum) in the United States, Europe, Asia, and Africa and for the stomach worm Abbreviata caucasia in Africa, Israel, Colombia, and Chile. Human cases involving these parasites are rare and cause no pathology.

COCKROACH ALLERGIES

It is only in recent years that the importance of cockroach allergies has been recognized. Allergic reactions result after initial sensitization to antigens following inhalation, ingestion, dermal abrasion, or injection. Allergens produced by cockroaches are rapidly being recognized as one of the more significant indoor allergens of modernized societies. Among asthmatics, about half are allergic to cockroaches. This rate is exceeded only by allergies to house-dust mites. Sensitivity to cockroaches also affects about 10% of nonallergic individuals, suggesting a subclinical level of allergy.

Symptoms exhibited by persons allergic to cockroaches are similar to those described by Wirtz (1980), who reported on occupational allergies in entomologists. They include sneezing and a runny nose, skin reactions, and eye irritation in about two-thirds of the cases. In the more severe cases, individuals may experience difficulty breathing or, even more alarming, anaphylactic shock following exposure to cockroaches. Such allergic reactions can be life-threatening (Brenner et al., 1991).

In recent years, research has focused on determining the specific components of cockroaches that cause allergy. Laboratory technicians exhibit strong allergies to cast skins and excrement of German cockroaches, whereas most patients seen at allergy clinics react primarily to cast skins and whole-body extracts of German cockroaches. Once an individual has become hypersensitized, he or she may experience severe respiratory distress simply by entering a room where cockroaches are held.

Several proteins that can cause human allergies have been identified in the German cockroach. Different exposure histories are likely to result in allergies to different proteins. Cast sldns, excrement, and partially consumed food of cockroaches, in addition to living cockroaches, all produce allergenic proteins. Some are extremely persistent and can survive boiling water, ultraviolet light, and harsh pH changes, remaining allergenically potent for decades. Traditionally, whole-body extracts have been used to screen for allergens in sldn tests and in bronchial challenges for diagnosing cockroach allergies

Cockroaches as Intermediate Hosts of Parasites of Veterinary Importance

(Fig. 3.13). However, use of more specific antigens that become aerosolized in cockroach-infested homes may be more appropriate, as this is likely to be the sensitizing material. Studies with laboratory colonies have shown that a population of several thousand German cockroaches produced several micrograms of aerosolized proteins in 48 hr. Consequently, the presence of cockroaches may have profound respiratory implications for asthmatic occupants of infested structures. For a general discussion on aerosolized arthropod allergens, see Solomon and Mathews (1988).

Development of an allergy to one insect species can result in broad cross-reactivity to other arthropods, including shrimp, lobster, crab and crawfish, sowbugs (isopods), and house-dust mites. Chronic indoor exposure to cockroach allergens, therefore, may have significant and widespread effects on human health.

VETERIN/ dkY IMPORTANCE

Cockroaches serve as intermediate hosts for a number of parasitic worms of animals (Table III). Most of these relationships are of no economic importance. The majority of the parasites are nematodes in the order Spirurida, all members of which use arthropods as intermediate hosts. Species infesting dogs and cats, among other hosts, attach to the mucosa of the gastrointestinal tract, where erosion of tissue may occur at the points of attachment.

Apparatus for conducting allergen tests using cockroaches. (Courtesy of R. J. Brenner, USDA/ARS)
FIGURE 3.13 Apparatus for conducting allergen tests using cockroaches. (Courtesy of R. J. Brenner, USDA/ARS)

Although serious damage seldom occurs, anemia and slow growth may result. Several cockroach-associated nematodes occur in Europe and North America. The esophageal worms Physaloptera rara and P. praeputialis are the most widespread species in the United States. They develop in the German cockroach, field crickets, and several species of beetles.

Poultry also are parasitized by nematodes which undergo development in cockroaches. The Surinam cockroach is the intermediate host for the poultry eye worms Oxyspirura mansoni and O. parvorum. Both occur in many parts of the world. In the United States, their distribution is limited to Florida and Louisiana. The German cockroach has been incriminated as the intermediate host for chicken and turkey parasites, including the stomach worms Tetrameres americana, T. fissispina, and Cyrnea colini; C. colini also develops in the American cockroach. C. colini apparently causes no significant damage to poultry, but Oxyspirura species can cause pathology ranging from mild conjunctivitis to severe ophthalmia with seriously impaired vision. T. fissispina can cause severe damage to the proventriculus of infested birds.

Several nematode parasites of rats and cattle utilize cockroaches as intermediate hosts (Table III). These include G. neoplasticum and Mastophorus muris in rodents. Both genera occur widely in the United States, where they cause no known pathological problems. The gullet worm of cattle, G. pulchrum, has been shown experimentally to undergo development in the German cockroach, although the usual arthropod hosts are coprophagous beetles.

Exotic zoo animals also can become infested with parasitic nematodes for which cockroaches serve as possible intermediate hosts. Protospirura bonnei and P. muricola, for example, have been found in cockroaches collected in cages of monkeys. In a case of “wasting disease” in a colony of common marmosets, more than 50% of German and brownbanded cockroaches captured in the animal room in which they were housed contained the coiled larvae of Trichospirura leptostoma in muscle cells (Beglinger et al., 1988).

Acanthocephalans (thorny-headed worms) commonly infest primates in zoos and research facilities. Prosthenorchis elegans and P. spirula occur naturally in South and Central America. Their natural intermediate hosts are unknown. In captivity, primates become infected after eating any of several cockroach species in which the intermediate stages of the parasite have completed development. Heavily infested primates frequently die within a few days. The proboscis of acanthocephalan adults commonly penetrates the intestines of the primate host, causing secondary infections, perforation of the gut wall, and peritonitis.

One pentastomid (tongue worm), Raillietiella hemidactyli, develops in cockroaches and reptilian hosts. In Singapore, infested geckos are a common occurrence in houses where heavy infestations of R. hemidactyli larvae have been found in American cockroaches. Remnants of cockroaches are found commonly in the guts of these lizards.

For additional information on the veterinary importance of cockroaches, see Chitwood and Chitwood (1950), Roth and Willis (1957), Levine (1968), and Noble and Noble (1976).

PREVENTION AND CONTROL

Traditionally, cockroaches have been controlled using a variety of toxic chemicals applied as residual pesticides to harborage sites or areas frequented by foraging individuals (see Ebling, 1975 and Rust et. al., 1995). Most materials are neurotoxins that disrupt the nervous system, causing locomotory and respiratory failure. These include organophosphates, carbamates, botanicals such as pyrethrins, and pyrethroids. Formulations include wettable powders, emulsifiable concentrates, crack-andcrevice aerosols, dusts, and baits. Several other materials with different modes of action also are currently in use. When ingested, boric acid (delivered as a fine powder or a dilute solution) damages the gut epithelium of cockroaches and kills them by interfering with nutrient absorption. Inorganic silica dust is absorptive, reducing cuticular lipids and causing desiccation. Active ingredients with other modes of action, such as hydramethylnon and sulfluramid, are metabolic inhibitors which disrupt the conversion of food to energy.

The use of baits containing many of the active ingredients mentioned above have been used extensively to control cockroaches. These baits are used indoors in the form of child-resistant bait stations to reduce human exposure. Other bait formulations of gels or pastes are used in crackand- crevice treatments, making them inaccessible to children and pets. Scatter baits are commonly used outdoors to treat mulches and other landscaping materials that harbor cockroaches.

Insect growth regulators (IGRs) can be used to prevent cockroaches from reaching maturity. Two commonly used IGRs are juvenile hormone analogs and chitin synthesis inhibitors. Juvenile hormone analogs regulate morphological maturation and reproductive processes. They are highly specific to arthropods, have very low mammalian toxicity, and are effective at exceptionally low rates of application. Such compounds include hydroprene and fenoxycarb. Chitin synthesis inhibitors prevent normal formation of chitin during molting. These compounds cause many of the affected nymphs to die during the molting process. Males that survive to the adult stage often have reduced life expectancies, whereas females tend to abort their oothecae.

Integrated pest management, which incorporates various control techniques, has contributed significantly to successful control of cockroaches. This approach uses nontoxic agents, such as sticky traps, vacuum devices, diatomaceous earth, or silica-gel repellents and desiccants, and manipulation of harborage sites to reduce or prevent infestations. Desiccants and dusts should be used only in geographic areas or situations with relatively low humidity; high humidity causes these materials to clump and lose their effectiveness. Building designs and construction techniques can significantly influence cockroach survival. By manipulating microclimates in discrete areas of structures frequented by cockroaches, homes and other buildings can be rendered less hospitable to pest species while at the same time greatly reducing aerosolized allergens. Nontoxic repellents can be used to deny access of cockroaches to specific areas.

Biological control of cockroaches has drawn increased attention in recent years. Among the natural agents that have been investigated are parasitic wasps, nematodes, and sporulating fungi. Females of the eulophid wasp Aprostocetus hagenowii and the evaniid wasp Comperia merceti deposit their eggs in the oothecae of certain peridomestic cockroaches. Major shortcomings in utilizing these wasps are difficulties involved in their mass production and the fact that they do not completely eliminate cockroach infestations. However, A. hagenowii has been shown to reduce populations of the peridomestic Periplaneta species following inundative or augmentative releases of this wasp. C. merceti parasitizes oothecae of the brownbanded cockroach and is the only known parasitoid of a domestic species. The use of parasitic nematodes (e.g., Steinernema carpocapsae) and several fungal pathogens that have been isolated from cockroaches has not yet proved to be effective as a practical management tool. Another drawback to their use is the allergenic nature of several components of nematodes and many sporulating fungi that can become airborne and, upon inhalation, cause asthmatic responses in humans.

Models have been developed for predicting population foci of peridomestic cockroaches based on physical characteristics of residential properties (Smith et al., 1995). However, the use of such models is limited by the scope of the data base used in its development and the complexity of the model itself. The use of traps to detect foci of cockroaches and the analysis of trap counts to determine cockroach abundance and distributional patterns can be helpful in assessing the extent of infestations and monitoring the effectiveness of control programs (Brenner and Pierce 1991).

Other Advocacy Entities

This section provides a short survey of industry advocacy and activities in support of 3DTV.

[email protected] Consortium

Recently (in 2008) the [email protected] Consortium was formed with the mission to speed the commercialization of 3D into homes worldwide and provide the best possible viewing experience by facilitating the development of standards, roadmaps, and education for the entire 3D industry—from content, hardware, and software providers to consumers.

3D Consortium (3DC)

The 3D Consortium (3DC) aims at developing 3D stereoscopic display devices and increasing their take-up, promoting expansion of 3D contents, improving distribution, and contributing to the expansion and development of the 3D market. It was established in Japan in 2003 by five founding companies and 65 other companies including hardware manufacturers, software vendors, contents vendors, contents providers, systems integrators, image producers, broadcasting agencies, and academic organizations.

European Information Society Technologies (IST) Project ‘‘Advanced Three-Dimensional Television System  Technologies’’ (ATTEST)

This is a project where industries, research centers, and universities have joined forces to design a backwards-compatible, flexible, and modular broadcast 3DTV system. The ambitious aim of the European Information Society Technologies (IST) project ATTEST is to design a novel, backwards-compatible, and flexible broadcast 3DTV system. In contrast to former proposals that often relied on the basic concept of “stereoscopic” video, that is the capturing, transmission, and display of two separate video streams (one for the left eye and one for the right eye), this activity focuses on a data-in-conjunction-with-metadata approach. At the very heart of the described new concept is the generation and distribution of a novel data representation format that consists of monoscopic color video and associated per-pixel depth information. From these data, one or more “virtual” views of a real-world scene can be synthesized in real-time at the receiver side (i.e., a 3DTV STB) by means of the DIBR techniques. The modular architecture of the proposed system provides important features, such as backwards-compatibility to today’s 2D DTV, scalability in terms of receiver complexity, and adaptability to a wide range of different 2D and 3D displays.

3D Content Creation. For the generation of future 3D content, novel three-dimensional material is created by simultaneously capturing video and associated per-pixel depth information with an active range camera such as the so-called ZCamTM developed by 3DV Systems. Such devices usually integrate a high-speed pulsed infrared light source into a conventional broadcast TV camera and they relate the time of flight of the emitted and reflected light walls to direct measurements of the depth of the scene. However, it seems clear that the need for sufficient high-quality, three-dimensional content can only partially be satisfied with new recordings. It will therefore be necessary (especially in the introductory phase of the new broadcast technology) to also convert already existing 2D video material into 3D using so-called “structure from motion” algorithms. In principle, such (offline or online) methods process one or more monoscopic color video sequences to (i) establish a dense set of image point correspondences from which information about the recording camera, as well as the 3D structure of the scene can be derived or (ii) infer approximate depth information from the relative movements of automatically tracked image segments. Whatever 3D content generation approach is used in the end, the outcome in all cases consists of regular 2D color video in European DTV format (720 × 576 luminance pels, 25 Hz, interlaced) and an accompanying depth-image sequence with the same spatiotemporal resolution. Each of these depth-images stores depth information as 8-bit gray values with the gray level 0 specifying the furthest value and the gray level 255 defining the closest value. To translate this data representation format to real, metric depth values (that are required for the “virtual” view generation (and to be flexible with respect to 3D scenes with different depth characteristics, the gray values are normalized to two main depth clipping planes.

3DV Coding. To provide the future 3DTV viewers with threedimensional content, the monoscopic color video and the associated per-pixel depth information have to be compressed and transmitted over the conventional 2D DTV broadcast infrastructure. To ensure the required backwards-compatibility with existing 2D-TV STBs, the basic 2D color video has to be encoded using the standard MPEG-2 as MPEG-4 Visual or AVC tools currently required by the DVB Project in Europe.

Transmission. The DVB Project, a consortium of industries and academia responsible for the definition of today’s 2D DTV broadcast infrastructure in Europe, requires the use of the MPEG-2 systems layer specifications for the distribution of audiovisual data via cable (DVB-C), satellite (DVB-S), or terrestrial (DVB-T) transmitters.

‘‘Virtual’’ View Generation and 3D Display. At the receiver side of the proposed ATTEST system, the transmitted data is decoded in a 3DTV STB to retrieve the decompressed color video- and depth-image sequences (as well as the additional metadata). From this data representation format, a DIBR algorithm generates “virtual” left- and right-eye views for the three-dimensional reproduction of a real-world scene on a stereoscopic or autostereoscopic, singleor multiple-user 3DTV display. The backwards-compatible design of the system ensures that viewers who do not want to invest in a full 3DTV set are still able to watch the two-dimensional color video without any degradations in quality using their existing digital 2DTV STBs and displays.

3D4YOU

3D4YOU7 is funded under the ICT Work Programme 2007–2008, a thematic priority for research and development under the specific program “Cooperation” of the Seventh Framework Programme (2007–2013). The objectives of the project are

  1. to deliver an end-to-end system for 3D high-quality media;
  2. to develop practical multi-view and depth capture techniques;
  3. to convert captured 3D content into a 3D broadcasting format;
  4. to demonstrate the viability of the format in production and over broadcast chains;
  5. to show reception of 3D content on 3D displays via the delivery chains;
  6. to assess the project results in terms of human factors via perception tests;
  7. to produce guidelines for 3D capturing to aid in the generation of 3D media production rules;
  8. to propose exploitation plans for different 3D applications.

The 3D4YOU project aims at developing the key elements of a practical 3D television system, particularly, the definition of a 3D delivery format and guidelines for a 3D content creation process.

The 3D4YOU project will develop 3D capture techniques, convert captured content for broadcasting, and develop 3D coding for delivery via broadcast that is suitable to transmit and make public. 3D broadcasting is seen as the next major step in home entertainment. The cinema and computer games industries have already shown that there is considerable public demand for 3D content but the special glasses that are needed limits their appeal. 3D4YOU will address the consumer market that coexists with digital cinema and computer games. The 3D4YOU project aims to pave the way for the introduction of a 3D TV system. The project will build on previous European research on 3D, such as the FP5 project ATTEST that has enabled European organizations to become leaders in this field.

3D4YOU endeavors to establish practical 3DTV. The key success factor is 3D content. The project seeks to define a 3D delivery format and a content creation process. Establishing practical 3DTV will then be demonstrated by embedding this content creation process into a 3DTV production and delivery chain, including capture, image processing, delivery, and then display in the home. The project will adapt and improve on these elements of the chain so that every part integrates into a coherent interoperable delivery system. A key project’s objective is to provide a 3D content format that is independent of display technology, and backward compatible with 2D broadcasting. 3D images will be commonplace
in mass communication in the near future. Also, several major consumer electronics companies have made demonstrations of 3DTV displays that could be in the market within two years. The public’s potential interest in 3DTV can be seen by the success of 3D movies in recent years. 3D imaging is already present in many graphics applications (architecture, mechanical design, games, cartoons, and special effects for TV and movie production).

In recent years, multi-view display technologies have appeared that improve the immersive experience of 3D imaging that leads to the vision that 3DTV or similar services might become a reality in the near future. In the United States, the number of 3D-enabled digital cinemas is rapidly growing. By 2010, about 4300 theaters are expected to be equipped with 3D digital projectors with the number increasing every month. Also in Europe, the number of 3D theaters is growing. Several digital 3D films will surface in the months and years to come and several prominent filmmakers have committed to making their next productions in stereo 3D. The movie industry creates a platform for 3D movies, but there is no established solution to bring these movies to the domestic market. Therefore, the next challenge is to bring these 3D productions to the living room. 2D to 3D conversion and a flexible 3D format are an important strategic area. It has been recognized that multi-view video is a key technology that serves a wide variety of applications, including free viewpoint and 3DV applications for the home entertainment and surveillance business fields. Multi-view video coding and transmission systems are most likely to form the basis for next-generation TV broadcasting applications and facilities. Multi-view video will greatly improve the efficiency of current video coding solutions performing simulcasts of independent views. This project builds on the wealth of experience of the major players in European 3DTV and intends to bring the date of the start of 3D broadcasting a step closer by combining their expertise to define a 3D delivery format and a content creation process.

The key technical problems that currently hamper the introduction of 3DTV to the mass market are as follows:

  1. It is difficult to capture 3DV directly using the current camera technology. At least two cameras need to operate simultaneously with an adjustable but known geometry. The offset of stereo cameras needs to be adjustable to
    capture depth, both close by and far away.
  2. Stereo video (acquired with 2-cameras) is currently not sufficient input for glasses-free, multi-view autostereoscopic displays. The required processing, such as disparity estimation, is noise-sensitive resulting in low 3D picture quality.
  3. 3D postproduction methods and 3DV standards are largely absenterimmature.

The 3D4YOU project will tackle these three problems. For instance, a creative combination of two or three high-resolution video cameras with one or two lowresolution depth range sensors may make it possible to create 3DV of good quality without the need for an excessive investment in equipment. This is in contrast to installing, say, 100 cameras for acquisition where the expense may hamper the introduction of such a system.

Developing tools for conversion of 3D formats will stimulate content creation companies to produce 3DV content at acceptable cost. The cost at which 3DV should be produced for commercial operation is not yet known. However, currently, 3DV production requires almost per frame user interaction in the video, which is certainly unacceptable. This immediately indicates the issue that needs to be solved: currently, fully automated generation of high 3DV is difficult; in the future it needs to be fully, or at least semi-automatic with an acceptable minimum of manual supervision during postproduction. 3D4YOU will research how to convert 3D content into a 3D broadcasting format and prove the viability of the format in production and over broadcast chains.

Once 3DV production becomes commercially attractive because acquisition techniques and standards mature, then this will impact the activities of content producers, broadcasters, and telecom companies. As a result, one may see that these companies may adopt new techniques for video production just because the output needs to be in 3D. Also, new companies could be founded that focus on acquiring 3DV and preparing it for postproduction. Here, there is room for differentiation since, for instance, the acquisition of a sport event will require large baselines between cameras and real-time transmission, whereas the shooting of narrative stories will require both small and large baselines and allows some manual postproduction for achieving optimal quality. These activities will require new equipment (or a creative combination of existing equipment) and new expertise.

3D4YOU will develop practical multi-view and depth capture techniques. Currently, the stereo video format is the de facto 3D standard that is used by the cinemas. Stereo acquisition may, for this reason, become widespread as an acquisition technique. Cinemas operate with glasses-based systems and can therefore use a theater-specific stereo format. This is not the case for the glasses-free autostereoscopic 3DTV that 3D4YOU foresees for the home. To allow glassesfree viewing with multiple people at home, a wide baseline is needed to cover the total range of viewing angles. The current stereo video that is intended for the cinema will need considerable postproduction to be suitable for viewing on a multi-view autostereoscopic display. Producing visual content will therefore, become more complex and may provide new opportunities for companies currently active in (3D) movie postproduction. According to the Networked and Electronic Media (NEM) Strategic Research Agenda, multi-view coding will form the basis for next-generation TV broadcast applications. Multi-view video has the advantage that it can serve different purposes. On the one hand, the multi-view input can be used for 3DTV. On the other hand, it can be shown on a normal TV where the viewer can select his or her preferred viewpoint of the action. Of course, a combination is possible where the viewer selects his or her preferred viewpoint on a 3DTV. However, multi-view acquisition with 30 views for example, will require 30 cameras to operate simultaneously. This initially requires a large investment. 3D4YOU therefore sees a gradual transition from stereo capture to systems with many views. 3D4YOU will investigate a mixture of 3DV acquisition techniques to produce an extended center view plus depth format (possibly with one or two extra views) that is, in principle, easier to produce, edit, and distribute. The success of such a simpler format relies on the ease (read cost!) at which it can be produced. One can conclude that the introduction of 3DTV to the mass market is hampered by (i) the lack of highquality 3DV content; (ii) by the lack of suitable 3D formats; and (iii) lack of appropriate format conversion techniques. The variety of new distribution media further complicates this.

Hence, one can identify the following major challenges that are expected to be overcome by the project:

  1. Video Acquisition for 3D Content: Here, the practicalities of multi-view and depth capture techniques are of primary importance, the challenge is to find the trade off such as number of views to be recorded, and how to
    optimally integrate depth capture with multi-view. A further challenge is to define which shooting styles are most appropriate.
  2. Conversion of Captured Multi-View Video to a 3D Broadcasting Format: The captured format needs new postproduction tools (like enhancement and regularization of depth maps or editing, mixing, fading, and compositing of V+D representations from different sources) and a conversion step generating a suitable transmission format that is compatible with used postproduction formats before the 3D content can be broadcast and displayed.
  3. Coding Schemes for Compression and Transmission: A last challenge is to provide suitable coding schemes for compression and transmission that are based on the 3D broadcasting format under study and to demonstrate their feasibility in field trials under real distribution conditions.

By addressing these three challenges from an end-to-end systems point of view, the 3D4YOU project aims to pave the way to the definition of a 3D TV system suitable for a series of applications. Different requirements could be set depending on the application, but the basic underlying technologies (capture, format, and encoding) should maintain as much commonality as possible so as to favor the emergence of an industry based on those technologies.

3DPHONE

The 3DPHONE project aims to develop technologies and core applications enabling a new level of user experience by developing end-to-end all-3D imaging mobile phone. Its aim is to have all fundamental functions of the phone—media display, User Interface (UI), and personal information management (PIM) applications—realized in 3D. We will develop techniques for all-3D phone experience: mobile stereoscopic video, 3D UIs, 3D capture/content creation, compression, rendering, and 3D display. The research and development of algorithms for 3D audiovisual applications including personal communication, 3D visualization, and content management will be done.

The 3DPhone Project started on February 11, 2008. The duration of the project is 3 years and there are six participants from Turkey, Germany, Hungary, Spain, and Finland. The partners are Bilkent University, Fraunhofer, Holografika, TAT, Telefonica, and University of Helsinki. 3DPhone is funded by the European Community’s ICT programme in Framework Programme Seven.

The goal is to enable users to

  • capture memories in 3D and communicate with others in 3D virtual spaces;
  • interact with their device and applications in 3D;
  • manage their personal media content in 3D.

The expected outcome will be simpler use and a more personalized look and feel. The project will bring state-of-the-art advances in mobile 3D technologies with the following activities:

  • A mobile hardware and software platform will be implemented with both 3D image capture and 3D display capability, featuring both 3D displays and multiple cameras. The project will evaluate different 3D display
    and capture solutions and will implement the most suitable solution for hardware–software integration.
  • UIs and applications that will capitalize on the 3D autostereoscopic illusion in the mobile handheld environment will be developed. The project will design and implement 3D and zoomable UI metaphors suitable for autostereoscopic displays.
  • End-to-end 3DV algorithms and 3D data representation formats, targeted for 3D recording, 3D playback, and real-time 3DV communication will beinvestigated and implemented.
  • Ergonomics and experience testing to measure any possible negative symptoms, such as eye strain created by stereoscopic content, will be performed. The project will research ergonomic conditions specific to the mobile handheld usage: in particular, the small screen, one hand holding the device, absence of complete keyboard, and limited input modalities.

In summary, the general requirements on 3DV algorithms on mobile phones are as follows:

  • low power consumption,
  • low complexity of algorithms,
  • limited memory/storage for both RAM and mass storage,
  • low memory bandwidth,
  • low video resolution,
  • limited data transmission rates and limited bitrates for 3DV signal.

These strong restrictions derived from terminal capabilities and from transmission bandwidth limitations usually result in relatively simple video processing algorithms to run on mobile phone devices. Typically, video coding standards take care of this by specific profiles and levels that only use a restricted and simple set of video coding algorithms and  low-resolution video. The H.264/AVC Baseline Profile for instance, uses only a simple subset of the rich video coding algorithms that the standard provides in general. For 3DV, the equivalent of such a low-complexity baseline profile for mobile phone devices still needs to be defined and developed. Obvious requirements of video processing and coding apply for 3DV on mobile phones as well, such as

  • high coding efficiency (taking bitrate and quality into account);
  • requirements specific for 3DV that apply for 3DV algorithms on mobile phones including
    • flexibility with regard to different 3D display types,
    • flexibility for individual adjustment of 3D impression.

 

 

TM-3D-SM Group of Digital Video Broadcast (DVB)

The DVB Project is an industry-led consortium of over 250 broadcasters, manufacturers, network operators, software developers, regulatory bodies, and others in over 35 countries committed to designing open technical standards for the
global delivery of DTV and data services. The DVB project is responsible for the definition of today’s 2D DTV broadcast infrastructure in Europe, requires the use of the MPEG-2 Systems Layer specification for the distribution of audiovisual
data via cable (DVB-C i.e., Digital Video Broadcast-Cable), satellite (DVB-S i.e., Digital Video Broadcast-Satellite), or terrestrial (DVB-T i.e., Digital Video Broadcast-Terrestrial) transmitters. Owing to its almost universal acceptance and
worldwide use, it is of major importance for any future 3DTV system, and to build its distribution services on this transport technology [16] (services using DVB standards are available on every continent with more than 500 million DVB receivers deployed).

During5 2009, DVB closely studied the various aspects of (potential) 3DTV solutions. A Technical Module Study Mission report was finalized, leading to the formal creation of the TM-3DTV group. A 3DTV Commercial Module has also now been created to go back to the first step of the DVB process: what kind of 3DTV solution does the market want and need, and how can DVB play an active part in the creation of that solution? To start answering some of these questions, the CM-3DTV group was planning to host a DVB 3D TV Kick-Off Workshop in early 2010.

There have already been broadcasts of a conventional display-compatible system, and the first HDTV channel compatible broadcasts are scheduled to start in Europe in spring 2010. In 2009, DVB had been closely studying the various aspects of (potential) 3DTV solutions. A Technical Module Study Mission report was finalized, leading to the formal creation of the TM-3DTV group. As the DVB process is business- and market-driven, a 3DTV Commercial Module has now also been created to go back to the first step: what kind of 3DTV solution does the market want and need, and how can DVB play an active part in the creation of that solution? To start answering some of these questions, the CM-
3DTV group hosted a DVB 3DTV Kick-off Workshop in Geneva in early 2010, followed immediately by the first CM-3DTV.

Advocacy for IPv6 Deployment—Example

We include below some excerpt from the European Economic and Social Committee and the Committee of the Regions [39] to emphasize the issues related to IPv6. Clearly, issues about IPv6 impact not only Europe but the entire world.

The European Economic and Social Committee and the Committee of the Regions has issued an “Action Plan for the deployment of IPv6 in Europe.” It is the objective of this Action Plan to support the widespread introduction of the next version of the IP (IPv6) for the following reasons:

  • Timely implementation of IPv6 is required as the pool of IP addresses provided by the current protocol version 4 is being depleted.
  • IPv6 with its huge address space provides a platform for innovation in IP based services and applications.

Preparing for the Growth in Internet Usage and for Future Innovation. One common element of the Internet architecture is the IP that in
essence gives any device or good connecting to the Internet a number, an address, so that it can communicate with other devices and/or goods. This address should generally be unique, to ensure global connectivity. The current version, IPv4, already provides for more than 4 billion such addresses. Even this, however, will not be enough to keep pace with the continuing growth of the Internet. Being aware of this long-term problem the Internet community developed an upgraded protocol, IPv6, which has been gradually deployed since the late 1990s.

In a previous Communication on IPv6, the European Commission made the case for the early adoption of this protocol in Europe. This Communication has been successful in establishing IPv6 Task Forces, enabling IPv6 on research networks, supporting standards, and setting-up training actions. Following the Communication, more than 30 European R&D projects related to IPv6 were financed. Europe has now a large pool of experts with experience in IPv6 deployment. Yet, despite the progress made, adoption of the new protocol has remained slow while the issue of future IP address scarcity is becoming more urgent.

Increasing Scarcity of IPv4 Addresses: A Difficulty for Users, an Obstacle to Innovation. Initially all Internet addresses are effectively held
by the IANA and then large blocks of addresses are allocated to the five RIRs that in turn allocate them in smaller blocks to those who need them, including ISPs. The allocation, from IANA to RIR to ISP, is carried out on the basis of demonstrated need: there is no preallocation.

The address space of IPv4 has been used up to a considerable extent. At the end of January 2008 about 16% was left in the IANA pool, that is, approximately 700 million IPv4 addresses. There are widely quoted and regularly updated estimates that forecast the exhaustion of the unallocated IANA pool somewhere between 2010 and 2011. New end users will still be able to get addresses from their ISP for some time after these dates, but with increasing difficulty.

Even when IPv4 addresses can no longer be allocated by IANA or the RIRs, the Internet will not stop working: the addresses already assigned can and most probably will be used for a significant time to come. Yet the growth and also the capacity for innovation in IP-based networks would be hindered without an appropriate solution. How to deal with this transition is currently the subject of discussion in the Internet community in general, and within and amongst the RIR communities in particular.

All RIRs have recently issued public statements and have urged the adoption of IPv6.

IPv4 is only a Short-Term Solution Leading to More Complexity. Concerns about the future scarcity of IP addresses are not a recent phenomenon. In the early days of the Internet, before the establishment of the RIRs and before the take-off of the World Wide Web, addresses were assigned rather generously. There was a danger of running out of addresses very quickly. Therefore, changes in allocation policy and in technology were introduced that allowed allocation to be more aligned to actual need.

One key IPv4 technology has been NAT. NATs connect a private (home or corporate) network that uses private addresses to the public Internet where public IP addresses are required. Private addresses come from a particular part of the address space reserved for that purpose. The NAT device acts as a form of gateway between the private network and the public Internet by translating the private addresses into public addresses. This method therefore reduces consumption of IPv4 addresses. However, the usage of NATs has two main drawbacks, namely:

  • It hinders direct device-to-device communication: intermediate systems are required to allow devices or goods with private addresses to communicate across the public Internet.
  • It adds a layer of complexity in that there are effectively two distinct classes of computers: those with a public address and those with a private address. This often increases costs for the design and maintenance of networks, as well as for the development of applications.

Some other measures could extend the availability of IPv4 addresses. A market to trade IPv4 addresses might emerge that would offer incentives to organizations to sell addresses they are not using. However IP addresses are not strictly property. They need to be globally acceptable to be globally routable, which a seller cannot always guarantee. In addition, they could become a highly priced resource. So far, RIRs have been skeptical about the emergence of such a secondary market. Another option consists of trying to actively reclaim those already-allocated address blocks that are underutilized. However, there is no apparent mechanism for enforcing the return of such addresses. The possible cost of it has to be balanced against the additional lifetime this would bring to the IANA pool. Though such measures may provide some interim respite, sooner or later the demand for IP addresses will be too large to be satisfied by the global IPv4 space. Efforts to stay with IPv4 too long risk increasing unnecessary complexity and fragmentation of the global Internet. A timely introduction of IPv6 is thus the better strategy.

IPv6: The Best Way Forward. IPv6 provides a straightforward and long-term solution to the address space problem. The number of addresses defined by the IPv6 protocol is huge. IPv6 allows every citizen, every network operator (including those moving to all IP “Next Generation Networks”), and every organization in the world to have as many IP addresses as they need to connect every conceivable device or good directly to the global Internet. IPv6 was also designed to facilitate features that were felt to be missing in IPv4. Those features included quality of service, autoconfiguration, security, and mobility. In the meantime, however, most of those features have been engineered in and around the original IPv4 protocol. It is the large address space that makes IPv6 attractive for future applications as this will simplify their design when compared to IPv4. The benefits of IPv6 are, therefore, most obviously apparent whenever a large number of devices or goods need to be easily networked, and made potentially visible and directly reachable over the Internet. A study funded by the Commission demonstrated this potential for a number of market sectors such as home networks, building management, mobile communication, defense and security sector, and car industry.

Prompt and efficient adoption of IPv6 offers Europe potential for innovation and leadership in advancing the Internet. Other regions, in particular the Asian region, have already taken a strong interest in IPv6. For instance, the Japanese consumer electronics industry increasingly develops IP enabled products and exclusively for IPv6. The European industry should therefore be ready to meet future demand for IPv6-based services, applications, and devices and so secure a competitive advantage in world markets.

To conclude, the key advantage of IPv6 over IPv4 is the huge, more easily managed address space. This solves the future problem of address availability now and for a long time to come. It provides a basis for innovation—developing and deploying services and applications that may be too complicated or too costly in an IPv4 environment. It also empowers users, allowing them to have their own
network connected to the Internet.

What Needs to be Done? IPv6 is not directly interoperable with IPv4. IPv6 and IPv4 devices can only communicate with each other using
application-specific gateways. They do not provide a general future-proof solution for transparent interoperability. However, IPv6 can be enabled in parallel with IPv4 on the same device and on the same physical network. There will be a transition phase (expected to last for 10, 20, or even more years) when IPv4 and IPv6 will coexist on the same machines (technically often referred to as “dual stack”) and be transmitted over the same network links. In addition, other standards and technologies (technically referred to as “tunneling”) allow IPv6 packets to be transmitted using IPv4 addressing and routing mechanisms and ultimately vice versa. This provides the technical basis for the step-by-step introduction of IPv6. Because of the universal character of the IP, deployment of IPv6 requires the attention of many actors worldwide. The relevant stakeholders in this process are as follows:

  • Internet organizations (such as ICANN, RIRs, and IETF) that need to manage common IPv6 resources and services (allocate IPv6 addresses, operate DNS servers, etc.), and continue to develop needed standards and specifications. As of May 2008, the regional distribution of allocated IPv6 addresses is concentrated on Europe (R´eseaux Internet Protocol Europ´eens or RIPE: 49%), with Asia and North America growing fast (Asia–Pacific Network Information Centre, APNIC: 24%; ARIN: 20%). Less than half of those
    addresses are currently being announced on the public Internet (i.e., visible in the default-free routing table). In the DNS the root and top-level name servers are increasingly becoming IPv6 enabled. For instance, the gradual introduction of IPv6 connectivity to. eu name servers started in 2008.
  • ISPs that need over time to offer IPv6 connectivity and IPv6 based services to customers: There is evidence that less than half of the ISPs offer some kind of IPv6 interconnectivity. Only a few ISPs have a standard offer for IPv6 customer access service (mainly for business users) and provide IPv6 addresses. The percentage of “Autonomous Systems” (typically ISPs and large end users) that operate IPv6 is estimated at 2.5%. Accordingly, IPv6 traffic seems to be relatively low. Typically the IPv6/v4 ratio is less than
    0.1% at Internet Exchange Points (of which about one in five supports IPv6). However, this omits direct ISP to ISP traffic and IPv6 that is “tunneled” and so appears at first glance to be still IPv4. Recent measurements suggest that this kind of traffic IPv6 that is “tunneled” is growing.
  • Infrastructure vendors (such as network equipment, operating systems, network application software) that need to integrate IPv6 capability into their products: Many equipment and software vendors have upgraded their products to include IPv6. However, there are still issues with certain functions and performance, and vendor support equivalent to IPv4. The installed equipment base of consumers, such as small routers and home modems to access the Internet, still by and large do not yet support IPv6.
  • Content and service providers (such as websites, instant messaging, email, file sharing, voice over IP) that need to be reachable by enabling IPv6 on their servers: Worldwide there are only very few IPv6 websites. Almost none of the global top sites offer an IPv6 version. The de facto nonexistence of IPv6 reachable content and services on the Internet is a major obstacle in the take-up of the new protocol.
  • Business and consumer application vendors (such as business software, smart cards, peer-to-peer software, transport systems, sensor networks) that need to ensure that their solutions are IPv6 compatible and increasingly need to develop products and offer services that take advantage of IPv6 features. Today, there are few, if any, current applications that are exclusively built on IPv6. One expectation has been that proliferation of IP as the dominant network protocol would drive IPv6 into new areas such as logistics and traffic management, mobile communication, and environment monitoring that has not taken place to any significant degree yet.
  • End users (consumers, companies, academia, and public administrations) that need to purchase IPv6 capable products and services and to enable IPv6 on their own networks or home Internet access: Many home end users, without being aware of it, operate IPv6 capable equipment and yet, as a result of missing applications, without necessarily making use of it. Companies and public administrations are cautious to make changes to a functioning network without a clear need. Therefore not much user deployment in private networks is visible. Among the early adopters have been universities and research institutions. All EU national research and education networks also operate on IPv6. The European G´eant network is IPv6 enabled, whereby approximately 1% of its traffic is native IPv6.

How much and which efforts are required to adopt IPv6 differ amongst actors and depend on each individual case. Therefore, it is practically impossible to reliably estimate the aggregated costs to introduce IPv6 globally. Experience and learning from projects have shown that costs can be kept under control when deployment is gradual and planned ahead. It is recommended that IPv6 be introduced step-by-step, possibly in connection with hardware and software upgrades, organizational changes, and training measures (at first glance unrelated to IPv6). This requires a general awareness within the organization in order to not miss those synergies. The costs will be significantly higher when IPv6 is introduced as a separate project and under time constraints.

Introduction of IPv6 will take place alongside the existing IPv4 networks. Standards and technology allow for a steady incremental adoption of IPv6 by the various stakeholders that will help to keep costs under control. Users can use IPv6 applications and generate IPv6 traffic without waiting for their ISP to offer IPv6 connectivity. ISPs can increase their IPv6 capability and offer this in line with perceived demand.

IPv6 Concepts

While it is likely that initially 3DTV will be delivered by traditional transport mechanisms, including DVB over DTH systems, recently some research efforts have been focused on delivery (streaming) of 3DTV using IP. IP can be used for IPTV systems or over an IP shared infrastructure, whether a private network (here shared with other applications) or over the Internet (here shared with a multitude of other users and applications) (some studies have also been undertaken of late on the capabilities of DVB-H to broadcast stereo-video streams.) However, it seems that the focus so far has been on IPv4; the industry is encouraged to assess the capabilities of IPv6. While this topic is partially tangential to a core 3DTV discussion, the abundant literature on proposals for packet-based delivery of future 3DTV (including but not limited to Refs [4–13]) makes the issue relevant. IPv6, when used with header compression, is expected to be a very useful technology to support IPTV in the future in general and 3DTV in particular. For a general discussion of IPTV and DVB-H, the reader may refer to Ref. [14] among other references.

IPv6 was defined in the mid-1990s in IETF Request for Comments (RFC) 2460 “Internet Protocol, Version 6 (IPv6) Specification” and a host of other more recent RFCs, is an “improved, streamlined, successor version” of IPv4.4 Because of market pull from the Office of Management and Budget’s mandate that 24 major federal agencies in the US Government (USG) be IPv6-ready by June 30, 2008, and because of market pull from European and Asian institutions, IPv6 is expected to see gradual deployment from this point forward and in the coming decade. With IPv6 already gaining momentum globally, with major interest and activity in Europe and Asia and also some traction in the United States; the expectation is that in the next few years a (slow) transition to this new protocol will occur worldwide. An IP-based infrastructure has now become the ubiquitous underlying architecture for commercial-, institutional-, and USG/Other (non-US)
Government (OG) communications and services functions. IPv6 is expected to be the next step in the industry’s evolution in the past 50 years from analog, to digital, to packet, to broadband. As an example of IPv6 deployment underway, Europe has set the objective to widely implement IPv6 by 2010; the goal is that at least 25% of users should be able to connect to the IPv6 Internet and to access their most important content and service providers without noticing a major difference when compared to IPv4.

IPv6 offers the potential of achieving increased scalability, reachability, endto- end interworking, QoS, and commercial-grade robustness for data communication, mobile connectivity, and for VoIP/triple-play networks. The current version of the IP, IPv4, has been in use successfully for almost 30 years and poses some challenges in supporting emerging demands for address space cardinality, high-density mobility, multimedia, and strong security. This is particularly true in developing domestic and defense department applications utilizing peer-to-peer networking. IPv6 is an improved version of IP that is designed to coexist with IPv4 while providing better internetworking capabilities than IPv4 [14–17].

When the current version of IPv4 was conceived in the mid-1970s and defined soon thereafter (1981), it provided just over 4 billion addresses; that is not enough to provide each person on the planet with one address without even considering the myriad of other devices and device modules needing addressability (such as but not limited to over 3 billion cellphones). Additionally, 74% of IPv4 have been assigned to North American organizations. The goal of developers is to be able to assign IP addresses to a new class of Internet-capable devices: mobile phones, car navigation systems, home appliances, industrial equipment, and other devices (such as sensors and Body-Area-Network medical devices). All of these devices can then be linked together, constantly communicating, even in wireless mode. Projections show that the current generation of the Internet will “run out of space” in the near future (2010/2011) if IPv6 is not adopted around the world. IPv6 is an essential technology for ambient intelligence and will be a key driver for a multitude of new, innovative mobile/wireless applications and services [18].

IPv6 was initially developed in the early 1990s because of the anticipated need for more end system addresses based on anticipated Internet growth, encompassing mobile phone deployment, smart home appliances, and billions of new users in developing countries (e.g., in China and India). New technologies and applications such as VoIP, “always-on access” (e.g., DSL and cable), Ethernet-tothe- home, converged networks, and evolving ubiquitous computing applications will continue to drive this need even more in the next few years [19].

IPv6 features, in comparison with IPv4, include the following [20]:

  • Expanded Addressing Capabilities: IPv6 increases the IP address size from 32 bits to 128 bits to support more levels in the addressing hierarchy, a much greater number of addressable nodes, and simpler autoconfiguration of addresses. The scalability of multicast routing is improved by adding a “scope” field to multicast addresses. A new type of address called an “anycast address” is also defined to be used to send a packet to any one of a group of nodes.
  • Header Format Simplification: Some IPv4 header fields have been dropped or made optional, to reduce the common-case processing cost of packet handling and to limit the bandwidth cost of the IPv6 header.
  • Authentication and Privacy Capabilities: In IPv6, security is built-in as part of the protocol suite: extensions to support authentication, data integrity (encryption), and (optional) data confidentiality are specified for IPv6. The security features of IPv6 are described in the Security Architecture for the Internet Protocol RFC 2401 [21], along with RFC 2402 [22] and RFC2406 [23]; Internet Protocol Security (IPsec) defined in these RFCs is required (mandatory). IPsec is a set of protocols and related mechanisms that supports confidentiality and integrity. (IPsec was originally developed as part of the IPv6 specification, but due to the need for security in the IPv4 environment, it has also been adapted for IPv4).
  • Flow Labeling Capability: A new feature is added to enable the labeling of packets belonging to particular traffic “flows” for which the sender requests special handling, such as non-default quality of service or “real-time” service. Services such as VoIP and IP-based entertainment video delivery (IPTV) is becoming broadly deployed and flow labeling, especially in the network core, can be very beneficial.
  • Improved Support for Extensions and Options: Changes in the way IP header options are encoded allows for more efficient forwarding, less stringent limits on the length of options, and greater flexibility for introducing new options in the future.

End systems (such as PCs, servers), network elements (customer-owned and/or carrier-owned) and (perhaps) applications need to be IPv6-aware to communicate in the IPv6 environment. IPv6 has been enabled on many computing platforms. At this juncture, many operating systems come with IPv6 enabled by default;  IPv6-ready Operating Systems (OS) include but are not limited to Mac OS X,
OpenBSD, NetBSD, FreeBSD, Linux, Windows Vista, Windows XP (Service Pack 2), Windows 2003 Server, and Windows 2008 Server. Java began supporting IPv6 with J2SE 1.4 (in 2002) on Solaris and Linux. Support for IPv6 on Windows was added with J2SE 1.5. Other languages, such as C and C++ also support IPv6. At this time the number of applications with native IPv6 support is significant given that most important networking applications provide native IPv6 support. Hardware vendors including Apple Computer, Cisco Systems,
HP, Hitachi, IBM, and Microsoft, support IPv6. One should note that IPv6 was designed with security in mind, but at the current time its implementation and deployment are (much) less mature than is the case for IPv4. When IPv4 was developed in the early 1980s, security was not a consideration; now a number of mechanisms have been added to address security considerations to IP. When IPv6 was developed in the early-to-mid 1990s, security was a consideration; hence, a number of mechanisms have been built-in into the protocol from the get-go to furnish security capabilities to IP.

A presentation delivered during an open session at the July 2007 ICANN Public Meeting in San Juan, Puerto Rico made note of the accelerated depletion rate of IPv4 addresses and the growing difficulties the Regional Internet Registries (RIRs) are experiencing in allocating contiguous address blocks of sufficient size to service providers. Furthermore, the fragmentation in the IPv4 address space
is taxing and stressing the global routing fabric and the near-term expectation is that the RIRs will impose more restrictive IPv4 allocation policies and promote a rapid adoption of IPv6 addresses [24]. The IPv4 address space is expected to run out by 2012.

 

DVB

DVB is a consortium of over 300 companies in the fields of broadcasting and manufacturing that work cooperatively to establish common international standards for digital broadcasting. DVB-generated standards have become the leading
international standards, commonly referred to as “DVB,” and the accepted choice for technologies that enable an efficient, cost-effective, high-quality, and interoperable digital broadcasting. The DVB standards for digital television have been adopted in the United Kingdom, across mainland Europe, in the Middle East, South America, and in Australasia. DBV standards are used for DTH satellite transmission 22 (and also for terrestrial and cable transmission).

The DVB standards are published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (Comit´e Europ´een de Normalisation Electrotechnique—CENELEC), and European Broadcasting Union (EBU). DVB produces specifications that are subsequently standardized in one of the European statutory standardization bodies. They cover the following DTV-related areas:

  • conditional access,
  • content protection copy management,
  • interactivity,
  • interfacing,
  • IP,
  • measurement,
  • middleware,
  • multiplexing,
  • source coding,
  • subtitling,
  • transmission.

Standards have emerged in the past 10 years for defining the physical layer and data link layer of a distribution system, as follows:

  • satellite video distribution (DVB-S and DVB-S2),
  • cable video distribution (DVB-C),
  • terrestrial television video distribution (DVB-T),
  • terrestrial television for handheld mobile devices (DVB-H).

Distribution systems differ mainly in the modulation schemes used (because of specific technical constraints):

  • DVB-S (SHF) employs QPSK (Quadrature Phase-Shift Keying).
  • DVB-S2 employs QPSK, 8PSK (Phase-Shift Keying), 16APSK (Asymmetric Phase-Shift Keying) or 32APSK; 8PSK is the most common at this time (it supports a 30-megasymbols pre-satellite transponder and provides a usable rate in the 75 Mbps range, or about 25 SD-equivalent MPEG-4 video channels).
  • DVB-C (VHF/UHF) employs QAM (Quadrature Amplitude Moderation): 64-QAM or 256-QAM.
  • DVB-T (VHF/UHF) employs 16-QAM or 64-QAM (or QPSK) along with COFDM (Coded Orthogonal Frequency Division Multiplexing).
  • DVB-H: refer to the next section.

Because these systems have been widely deployed, especially in Europe, they may well play a role in the near-term 3DTV services. IPTV also makes use of a number of these standards, particularly when making use of satellite links (an architecture that has emerged is to use satellite links to provide signals to various geographically distributed headends, which then distribute these signals terrestrially to a small region using the telco IP network—these headends act as rendezvous point in the IP Multicast infrastructure). Hence, in the reasonable assumption that IPTV will play a role in 3DTV, these specifications will also be considered for 3DTV in that context.

As implied above, transmission is a key area of activity for DVB. See Table 4.2 for some of the key transmission specifications.

In particular, EN 300 421 V1.1.2 (1997–2008) describes the modulation and channel coding system for satellite digital multiprogram television (TV)/HDTV services to be used for primary and secondary distribution in Fixed Satellite Service (FSS) and Broadcast Satellite Service (BSS) bands. This specification is also known as DVB-S. The system is intended to provide DTH services for consumer IRD, as well as cable television headend stations with a likelihood
of remodulation. The system is defined as the functional block of equipment performing the adaptation of the baseband TV signals, from the output of the MPEG-2 transport multiplexer (ISO/IEC DIS 13818-1) to the satellite channel characteristics. The following processes are applied to the data stream:

  • transport multiplex adaptation and randomization for energy dispersal;
  • outer coding (i.e., Reed–Solomon);
  • convolutional interleaving;
  • inner coding (i.e., punctured convolutional code);
  • baseband shaping for modulation;
  • modulation.

DVB-S/DVB-S2 as well as the other transmission systems could be used to deliver 3DTV. As seen in Fig. 4.9, MPEG information is packed into PESs (Packetized Elementary Streams), which are then mapped to TSs that are then handled by the DVB adaptation. The system is directly compatible with MPEG- 2 coded TV signals. The modem transmission frame is synchronous with the MPEG-2 multiplex transport packets. Appropriate adaptation to the signal formats (e.g., MVC ISO/IEC 14496-10:2008 Amendment 1 and ITU-T Recommendation H.264, the extension of AVC) will have to be made, but this kind of adaptation has recently been defined in the context of IPTV to carry MPEG-4 streams over an MPEG-2 infrastructure (Fig. 4.10).

Key DVB Transmission Specifications

Key DVB Transmission Specifications

For Digital Rights Management (DRM), the DVB Project–developed Digital Video Broadcast Conditional Access (DVB-CA) defines a Digital Video Broadcast Common Scrambling Algorithm (DVB-CSA) and a Digital Video Broadcast Common Interface (DVB-CI) for accessing scrambled content:

  • DVB system providers develop their proprietary conditional access systems within these specifications;
  • DVB transports include metadata called service information (DVB-SI i.e., Digital Video Broadcast Service Information) that links the various Elementary Streams (ESs) into coherent programs and provides human-readable descriptions for electronic program guides.

Functional block diagram of DVB-S.

Mapping of MPEG-2/MPEG-4 to DVB/DVB-S2 systems.

Opportunities and Challenges for 3DTV

The previous section highlighted that many of the components needed to support an end-to-end commercial broadcast service are available or are becoming available. Hence, proponents see a significant market opportunity at this time. CEA
estimates that more than 25% of sets sold in 2013 will be 3D-enabled. A handful of representative quotes from proponents of the 3D technology are as follows:

No one can escape the buzz and excitement around 3D. We’re witnessing the start of
dramatic change in how we view TV—the dawn of a new dimension. And through Sky’s
clear commitment to 3D broadcasting, 3D in the home is set to become a reality . . . .

. . . The next killer application for the home entertainment industry—3DTV . . . [It]
will drive new revenue opportunities for content creators and distributors by enabling
3D feature films and other programming to be played on their home television and
computer displays—regardless of delivery channels . . . .

. . . The most buzzed about topics at CES: 3-D stereoscopic content creation . . . Several
pivotal announcements [in] 2010 including 3D-TV releases from the major consumer
electronics manufacturers and the launch of several dedicated 3D broadcast channels
are driving the rapid increase in demand for 3-D content . . .

3D technology is now positioned “to become a major force in future in-home entertainment.”

. . . 3DTV is one of the ‘hottest’ subjects today in broadcasting. The combination of
the audience’s‘wow’ factor and the potential to launch completely new services, makes
it an attractive subject for both consumer and professional. There have already been
broadcasts of a conventional display-compatible system, and the first HDTV channel
compatible broadcasts are scheduled to start in Europe in the Spring of 2010 . . .

. . . In Europe, the EC is currently funding a large series of projects for 3DTV, including
multiview, mobile 3D and 3D search . . .

time, there are industry observers that take a more conservative view. These observers make note that there are uncertainties about the availability of content, the technological readiness, and acceptance in the living room, especially given the requirement to use polarized or shutter glasses. A rational approach to market penetration is certainly in order; also, the powerful tool of statistically valid market research can be used to truly measure user interest and willingness to pay. Some representative quotes for a more conservative view of the 3D technology are given below:

. . . In a wide range of demos, companies . . . claim . . . in January 2010 that stereoscopic
3D is ready for the home. In fact, engineers face plenty of work hammering out
the standards and silicon for 3DTV products, most of which will ship for the holiday
2010 season . . .

It has proven somewhat difficult to create a 3D system that does not cause ‘eye fatigue’
after a certain time. Most current-generation higher resolution systems also need special
eyeglasses which can be inconvenient. Apart from eye-fatigue, systems developed
so far can also have limitations such as constrained viewing positions. Multiple viewpoint
television systems are intended to alleviate this. Stereoscopic systems also allow
only limited ‘production grammar’ . . . One should not underestimate the difficulty, or
the imagination and creativity required, to create a near ‘ideal’ 3DTV system that the
public could enjoy in a relaxed way, and for a long period of time . . .

. . . The production process for 3D television requires a fundamental rethinking of the
underlying technology. Scenes have to be recorded with multiple imaging devices that
may be augmented with additional sensor technology to capture the three-dimensional
nature of real scenes. In addition, the data format used in 3D television is a lot more
complex. Rather than normal video streams, time-varying computational models of the
recorded scenes are required that comprise of descriptions of the scenes’ shape, motion,
and multiview appearance. The reconstruction of these models from the multiview
sensor data is one of the major challenges that we face today. Finally, the captured
scene descriptions have to be shown to the viewer in three-dimensions which requires
completely new display technology . . .

. . . The conventional stereoscopic concept entails with two views: it relies on the basic
concept of an end-to-end stereoscopic video chain, that is, on the capturing, transmission
and display of two separate video streams, one for the left and one for the
right eye. [Advocates for the autostereoscopic approach argue that] this conventional
approach is not sufficient for future 3DTV services. The objective of 3DTV is to bring
3D imaging to users at home. Thus, like conventional stereo production and 3D Cinema,
3DTV is based on the idea of providing a viewer with two individual perspective
views—one for the left eye and one for the right eye. The difference in approaches,
however, lies in the environment in which the 3D content is presented. While it seems
to be acceptable for a user to wear special glasses in the darkened theatrical auditorium
of a 3D Digital Cinema, [many, perhaps] most people would refuse to wear such
devices at home in the communicative atmosphere of their living rooms. Basically,
auto-stereoscopic 3D displays are better suited for these kinds of applications

. . . The two greatest industry-wide concerns [are]: (1.) That poor quality stereoscopic
TV will‘poison the water’ for everyone. Stereoscopic content that is poorly realized in
grammar or technology will create a reputation of eyestrain which cannot be shaken
off. This has happened before in the 30s, the 50s, and the 80s in the cinema. (2.) That
fragmentation of technical standards will split and confuse the market, and prevent
stereoscopic television from ever being successful . . .

. . . people may quickly tire of the novelty. I think it will be a gimmick. I suspect there
will be a lot of people who say it’s sort of neat, but it’s not really comfortable . . .

The challenge for the stakeholder is to determine where the “true” situation is, whether it is at one extreme, at the other extreme, or somewhere in the middle. An abbreviated list of issues to be resolved in order to facilitate broad deployment
of 3DTV services, beyond pure technology and encoding issues, include the following :

  • Production grammar (3D production for television still in infancy)
  • Compatibility of systems (also possibly different issues for pay TV and free-to-air operators)
  • Assessment of quality/suitability
    • Methodologies for the quality assessment of 3D TV systems;
    • Parameters that need to be measured that are specific to 3D TV;’
    • Sensation of reality;
    • Ease of viewing.
  • Understanding what the user requirements are.

In general, a technology introduction process spans three phases:

  • Phase 1: The technology becomes available in basic form to support a given service;
  • Phase 2: A full panoply of standards emerges to support widespread deployment of the technology;
  • Phase 3: The technology becomes inexpensive enough to foster large-scale adoption by a large set of end-users.

With reference to 3DTV, we find ourselves at some early point in Phase 1. However, there are several retarding factors that could hold back short-term deployment of the technology on a broad scale, including deployment and service cost (overall status of the economy), standards, content, and quality.

The previous assertion can be further elaborated as follows: ITU-R WP 6C classifies 3D TV systems into two groups. The “first generation” systems are essentially those based on “Plano-stereoscopic” display of single or multiple discrete lateral left and right eye pictures. Recommendations for such systems should be possible in the near future. The “second generation” systems are those which are based on object-wave recording (holography) or approximations of object-wave recording. Recommendations for such systems may be possible in the years ahead. We refine these observations by defining the following generations of 3DTV technology:

  • Generation 0: Anaglyth TV transmission;
  • Generation 1: 3DTV that supports plano-stereoscopic displays, which are stereoscopic (that is, require active or passive glasses);
  • Generation 2: 3DTV that supports plano-stereoscopic displays, which are autostereoscopic (do not require glasses);

Three epochs of 3DTV commercial deployment.

  • Generation 2.5: 3DTV that supports plano-stereoscopic displays, which are autostereoscopic (do not require glasses) and support multiple (N = 9) views;
  • Generation 3: 3DTV that supports integral imaging, transmission, and displays;
  • Generation 4: 3DTV that supports volumetric displays, transmission, and displays;
  • Generation 5: 3DTV that supports object-wave transmission.

See Figs. 1.9 and 1.10 (partially based on Ref. 2). Whether and when we get beyond Generation 2.5 in this decade remains to be seen. This text, and the current commercial industry efforts concentrate on Generation 1 services. At press time, we find ourselves in Phase 1 of Generation 1. The existing commercial video infrastructure can handle 3D video in a basic, developmental form; however, providing HD 3D with motion graphics is not achievable without making enhancements to such infrastructure. Existing infrastructures, including satellite and/or terrestrial distribution networks for example, can handle what some have termed “half-HD resolution” per eye, or frame formats of 1080i, 1080p24, and 1080i60. Existing encoders and set-top boxes can be used as long as signaling issues are addressed and 3D content is of a consistent form. The drawback of half-HD resolution is that images can be blurry, especially for sporting events and high-action movies [20]. New set-top chip sets are required for higher resolution 3DTV.

 

Environmental benefits

Public cloud computing is often touted as an environmentally friendly or ‘green’ alternative to businesses owning their own IT infrastructures, but there are arguments for and against this claim. Sharing resources and commuting less must be a good thing, but if the enhanced technology that is available in public clouds causes businesses to use more resources together than the combined total they would have used apart then how can they be green?

Sharing resources

Some arguments for cloud computing being an energyefficient IT solution are:

  • customers share a pool of IT resources;
  • suppliers are using bigger, more modern and energyefficient data centres in purpose-built ‘smart’ buildings;
  • increased utilization of servers due to server virtualization – vendors claim that typical server utilization rates can rise from between 5 and 15 per cent to between 60 and 80 per cent (VMWare, 2010);
  • the financial incentives for cloud providers to use less energy;
  • the increasing availability of follow-the-sun and follow-the-moon clouds so virtual servers and applications move between linked data centres across time zones, making more use of the combined computing resources and even taking account of the availability of energy in different geographical locations at certain times of day.

Some arguments against cloud computing technologies being green are:

  • more internet traffic;
  •  increased data replication within public clouds;
  •  high demand created by new services.

According to a March 2010 Greenpeace report, Make IT Green: Cloud Computing and its Contribution to Climate Change, the electricity consumed by cloud computing globally will increase from 623 billion kilowatt hours in 2007 to 1,964 billion kWh by 2020 (Greenpeace, 2010).

Now, the clock cannot be turned back, the cloud computing ‘genie’ cannot go back into the bottle. We have to accept that internet usage will increase along with the wider adoption of cloud computing services, but the rise of social networking websites has made this an inevitable trend anyway. All we can do is to make the technology we use to provide web-based services as green as possible, and cloud computing providers can certainly help. Along with many leading IT firms, Google and Microsoft are members of the Climate Savers Computing Initiative (http://www.climatesaverscomputing.org/), which is a nonprofit group ‘dedicated to reducing the energy consumption
of computers and reducing the environmental impact of new and emerging technologies’, so let us hope they can rise to
the significant challenge that cloud computing represents.

Reduced travel

Naturally, cloud computing means that we no longer have to travel to an office to do office work, nor do our system
administrators have to go to data centres to install new servers. It is now much easier to work from home and many of us do already – in the UK, for example, at least 8 per cent of the workforce in 2005 used computers and  elecommunications to work mainly from home (Ruiz and Walling, 2005). If global warming is a reality, as most of the scientists of our time agree, then I would like to think that cloud computing or ‘cloud commuting’ will help to make most business travel unnecessary and reduce significantly the impact of business activities on the environment, but only time will tell. According to Viviane Reading, EU Commissioner for Information Society and Media: ‘If businesses in Europe were to replace only 20 per cent of all business trips by video conferencing, we could save more than 22 million tons of CO2 per year’ (Donaghue, 2009).

tons of CO2 per year’ (Donaghue, 2009). I first wrote about ‘cloud computing commuters’ in my blog post of 19 February 2009, concluding it with speculation about their possible effect on cities:

I can predict with more confidence that, although there will always be value in face-to-face meetings, there will be far lesstime, money and energy wasted on commuting in the decade to come. London’s workforce will consist increasingly ofvirtual commuters, doing ever more complex business in the cloud. Whether London itself, or cities in general, will still be as important in the business world is another matter, and it may all depend on those cloud computing commuters.(Williams, 2009)

 

Benefits of cloud computing

I see, therefore, great potential for cloud computing applications to help Europe’s businesses into the true ICT age, at lower costs compared to traditional IT company solutions.

Viviane Reding, EU Commissioner for Information Society and Media, November 2009

Towards the end of the first decade of the 21st century there was a worldwide financial crisis that saw businesses everywhere searching for ways to cut costs. At the same time feature-rich ‘Web 2.0’ technologies such as social networking
websites, accessible from anywhere on different kinds of devices – including the ubiquitous iPhone from Apple – were gaining in popularity at an incredible rate, thanks in no small part to the high availability and affordability of broadband internet and mobile internet connections. So Information Technology was becoming more complex and businesses, along with the general public, were becoming ever more dependent on it; but added complexity and functionality are usually accompanied by added costs, which was not a great message for financial directors in a recession. The time was right for cloud computing, which offers some businesses considerable financial benefits, technological benefits and operational benefits, and can provide an opportunity for competitive advantage over others. As for the potential environmental benefits of cloud computing, they are debatable, as we shall see.