Description Of Dorsal View Of Fowl

FIGURE 23.4 Chicken mite, Dermcmyssusgnllime (Dermanyssidae), female, ventral view. (Modified from Gorham, 1991 courtesy of the US Department of Agriculture.)

and Liponyssoides. They are ectoparasites primarily on wild and domestic rodents and birds. These mites feed on the blood of their hosts by piercing the skin with their long, slender, extrusible chelicerae with highly reduced chelae at their tips. Dermanyssids spend most of their time in the nests of their hosts, crawling onto the animals primarily to feed. When they come into contact with human skin, they are prone to bite, typically causing erythematous papules at each puncture site that are often accompanied by intense itching.

Chicken mite (Dermanyssusgallincte) Also called the red poultry mite, this cosmopolitan species (Fig. 23.4) is the most common dermanyssid mite that bites people. It parasitizes a very broad range of hosts. This mite is especially a problem in the Palaearctic region and in the United States, where most cases occur in poultry houses or around buildings where pigeons, house sparrows, or starlings are nesting. The mites live in nesting materials, where they spend most of their time, moving onto the birds to feed on blood at night. Consequently, workers in poultry operations seldom experience a biting problem while working during the daytime, even when the houses are heavily infested. However, individuals who enter infested buildings at night may be readily bitten. Occasionally, pet canaries and parakeets also serve as sources of human infestations.

The term pigeon mite refers to D. gallincie when it infests pigeons or rock doves. The mites frequently enter buildings from pigeon roosts or nests. This tends to happen in the late spring and early summer months presence of mites is confirmed. WEE virus has been isolated from these mites infesting nests of the house sparrow, but its significance in transmission or maintenance of WEE virus is unknown.

when the young pigeons fledge and the nests are abandoned, forcing the mites to seek alternative hosts. Although most human bites occur at night, bites may occur during the daytime when buildings are darkened.

A number of cases have been reported in hospitals and other institutional settings where employees and patients have been bitten by D. gallinae. The sources of the problem generally can be traced to nesting birds, notably pigeons, on windowsills, on ledges, under eaves, in air-intake ducts, or on air-conditioners mounted on the outside walls. The mites enter rooms around windows and doors, through crevices and cracks, or via ventilation ducts and air-conditioning systems. In other situations, they may drop onto individuals from roosting or nesting birds in ceilings or from overhead sites on porches and walkways near buildings. In such cases, close inspection may reveal mites crawling on clothing, furniture, or bed linens, particularly at night, when the mites are active.

Human infestations with D. gallinae have been variously called chicken tick rush, bird mite disease, psora dermanyssica, pseudogale, and gamasidosis. The term fowl mite dermatitis is likewise used but also can be applied to skin reactions caused by other avian mites that attack people.

Most bites tend to occur on the arms and chest protected by clothing, rather than on exposed skin such as the hands and face. Only in exceptional cases do bites occur in the axillary and pubic areas. The bites are usually painful and typically result in red maculopapular skin lesions on the upper portions of the body and extremities. While a human is being bitten, close examination will reveal the mite as a tiny red speck at the center of the papule. Occasionally the bites produce vesicles, urticarial plaques, and diffuse erythema, with dermatographia being frequently seen. In multiple-bite cases, a pruritic rash may develop and persist until the source of the infestation has been eliminated. Itching tends to be most intense at night, The problem is usually resolved by treatment with antihistamines or topically applied steroids, combined with moving individuals from affected areas.

St. Louis encephalitis (SLE), eastern equine encephalitis (EEE), and western equine encephalitis (WEE) viruses have been isolated from D. gallinae infesting wild birds. However, conflicting evidence has been reported regarding the ability of D. gallinae to transmit any of these viruses among birds or to humans.

American bird mite (Dermanyssus americanus)

This mite is very closely related to D. gallinae but only rarely has been reported biting humans. It can cause acute, generalized, eczematous dermatitis which is easily misdiagnosed as other skin disorders unless the

Dermanyssus hirundinis This hematophagous mite is a common ectoparasite of certain birds, especially swallows (Hirundo spp.) and the house wren (Troglodytes aedon) in North America and Europe. It is not unusual for hundreds or thousands of these mites to infest individual nestling birds. At least one case has been documented in Europe of D. hirudinis biting a human and causing urticarial dermatitis (Dietrich and Horstmann, 1983).

House mouse mite (Liponyssoides sanguineus)

This mite (Fig. 23.5), referred to in the earlier literature as Alio dermanyssus sanguineus, is an ectoparasite of domestic and wild rodents. It commonly parasitizes mice, including the house mouse (Mus musculus),

FIGURE 23.5 House mouse mite, Liponyssoides sanguineus (Dermanyssidae), female, ventral view. Note the pair of long, attenuated, extruded chelicerae with serrated tips for piercing skin to feed on blood. {Modified from Baker et al., 1956)

Scapula Fowl

FIGURE 23.5 House mouse mite, Liponyssoides sanguineus (Dermanyssidae), female, ventral view. Note the pair of long, attenuated, extruded chelicerae with serrated tips for piercing skin to feed on blood. {Modified from Baker et al., 1956)

in the United States and the spiny mouse (Acomys spp.) in North Africa. It occurs less commonly on rats (Rattus spp.), voles (Microtia spp.), and other rodents in localized areas of eastern North America, Europe, Asia, and Africa. It is primarily of interest to medical entomologists because of its role as the vector of Rickettsia akari, the etiologic agent of rickettsialpox in humans.

Like most other dermanyssid mites, the house mouse mite lives in nesting materials, where it spends most of its time, crawling onto host animals to feed. Its life cycle and behavior are similar in many respects to those of D.gallinae. Females oviposit in rodent nests or along rodent runways 2—5 days after feeding on host blood. The eggs hatch in 4—5 days to produce larvae which do not feed but instead molt to protonymphs about 3 days later. The protonymphal stage lasts 4—5 days, during which time the mite takes a blood meal, usually engorging in less than an hour, and then molts to the deutonymph. The deutonymph lives about 6-10 days and requires a blood meal before transforming to the adult. The developmental time from egg to adult normally takes 2—3 weeks. After feeding, blood-engorged females leave the rodent host and can be found in the nests and runways, along the walls of infested premises, and especially in warmer areas of buildings, such as furnace and incinerator rooms.

Macronyssidae

Macronyssid mites are blood-feeding ectoparasites on reptiles, birds, and mammals. Five species account for most of the cases of medical interest. Three of these are Ornithonyssus species infesting rodents or birds; Chiroptonyssus is parasitic on bats, whereas Ophionyssus is parasitic on snakes.

Tropical rat mite (Ornithonyssus bacoti)

This cosmopolitan mite (Fig. 23.6) is a parasite of rats, particularly the black rat (Rattus rattus), and other rodents in both tropical and temperate regions. In cooler climates this mite occurs only indoors and in nests of wild rodents, Occasionally it also infests carnivores, birds, and humans. When rats are killed or abandon their nests or runways, the mites are left behind and will readily crawl or drop onto humans and other passing animals. Rodents killed by household cats and left near human dwellings also can serve as a source of infestation, The mites are active and can move some distance from their source to enter nearby buildings.

Human bite cases involving the tropical rat mite usually occur in rodent-infested buildings. Using their long, slender chelicerae, they probe the sldn in an effort to feed on blood. In some cases they produce a prickling sensation at the bite sites, whereas in other cases

Ornithonyssus Bacoti
FIGURE 23.6 Tropical rat mite, Ornithonyssus bacoti (Macronyssidae), female, ventral view. (Modified from Gorham, 1991; courtesy of the US Department of Agriculture.)

the bite is painful. Multiple bites are often clustered and subsequently develop into a pruritic, erythematous, papular rash. This may be accompanied by localized swelling and occasional vesicle formation. Although they will bite almost any part of the body, they tend to bite where the clothing is tight; e.g., neck, shoulders, and waist. O. bacoti is visible to the unaided eye and may be seen crawling on the clothing or skin, floors, walls, and other structural surfaces.

This mite has been shown experimentally to be capable of being infected with, or transmitting, several human pathogens, including those that cause murine typhus, rickettsialpox, plague, tularemia, and coxsackie virus disease. However, their importance in the epidemiology of these diseases is regarded as negligible. On the other hand, recent evidence supports the possibility that O, bacoti may serve as both a vector and reservoir of Hantaan virus, the causative agent of Korean hem orrhagic fever (epidemic hemorrhagic fever) of humans in Asia.

Tropical fowl mite (Ornithonyssus bursa) As its common name implies, the tropical fowl mite (Fig. 23.7) is distributed widely throughout subtropical and tropical parts of the world, where it parasitizes various domestic and wild birds. It occurs in the eastern and southern United States, Hawaii, Central America, Colombia, South Africa, India, China, and

Ornithonyssus Sylviarum Bursa Bacoti
FIGURE 23,8 Northern fowl mite, Ornithonysms sylviarum (Macronyssidae), female. (A) Dorsal view; (B) ventral view. (Modified from Strandtmann and Wharton, 1958)
Tropical Rat Mite Attached Human Skin

Human bites occur primarily in reptile houses at zoological parks, affecting personnel who handle infested snakes. A well-documented case involved several members of a family in a household where a python was kept as a pet (Schultz, 1975). The family members had experienced skin lesions in the form of a papular rash on the forearms and other parts of the body over a 5-month period before the source of the problem was identified. Mites were observed to be attached to the skin while attempting to feed and also were found in a chair frequented by the snake. Humans do not serve as suitable hosts for this mite. The mites tend to become immobile with their legs curled underneath the body within a few minutes after they begin feeding on human blood; often they do not recover. They do not transmit any known human pathogens.

Laelapidae

Members of this family include both free-living and parasitic species, often associated with rodents and other nestbuilding mammals. The only significant laelapid species that may affect human health is the spiny rat mite. Occasionally other species cause temporary discomfort to humans, as reported in possible cases of Haemogamasuspon-tiger causing dermatitis in England (Theiler and Downes, 1973).

The laelapid Haemogamasus liponyssoidesis an obligate blood feeder on wild rodents which has the potential for transmitting human disease agents, even though it has not been reported to bite people (Furman, 1959). Other rodent-associated laelapid mites may play a role in the transmission of Hantaan virus, the causative agent of Korean hemorrhagic fever, based on isolation of this human pathogen from Laelaps jettmari in Korea (Traub etal., 1954).

Spiny rat mite (Laelaps echidninus) The spiny rat mite is a common hematophagous ectoparasite of domestic rats throughout the tropical and temperate zones. Although it is capable of biologically transmitting disease agents, such as the agent of murine typhus, among wild rodents, its potential role as a vector of human pathogens remains uncertain. Junin virus, which causes Argentinian hemorrhagic fever, has been isolated from L. echidninus and associated rodent hosts in South America (Parodi et ai, 1959; Theiler and Downes, 1973).

Trombiculidae

Larvae of members of the family Trombiculidae are called chiggers. This is the only parasitic stage in the life cycle of trombiculid mites. As a group, they feed on a wide variety of vertebrate hosts, including amphibians, reptiles,

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