Dermanyssus gallinae (DeGeer, 1778)
ETYMOLOGY:Derma = skin and nyssus = to prick; along with gallinae for the chicken host
HISTORY:Dermanyssus gallinae, which primarily affects avians, was first described by DeGeer in 1778. This mite infests cats only occasionally (Grant, 1985).
GEOGRAPHIC DISTRIBUTION: The mite is worldwide in its distribution, attacking the fowl, pigeon, canary and other cage birds (Harwood and James, 1979).
LOCATION IN HOST:Dermanyssus gallinae is a nonburrowing, blood-sucking mite that usually infests birds or their domiciles (Regan et al., 1987). This mite on rare occasions is found within the haircoat of cats (Grant, 1985). A case of this mite infesting the cat in the United States revealed lesions consisting of erosions, crusts, and excoriations on the head (Muller et al., 1983). Grant (1989) reports lesions on the dorsum and the extremities of the cat.
IDENTIFICATION:Dermanyssus gallinae is often referred to as the red mite of poultry, but it is only red if it has recently fed on its host's blood. In the unfed state, this mite is white, grey or black. The fully engorged adult female is about 1 mm long or longer (Fig. 5-19). All other developmental stages are smaller. This mite possesses a very prominent dorsal shield. The shield does not quite extend to the posterior end of the body and its posterior end is truncated. The hairs on the dorsal shield are smaller than those on the carapace that surrounds the shield. On the posterior ventral surface of the mite is a prominent anal plate; the anus is located on the posterior aspect of this plate. This mite possessed long, whip-like chelicerae. Many of these key morphologic features can only be visualized after the mites have been cleared in lactophenol and examined under a compound microscope.
LIFE CYCLE: The majority of this mite's life cycle takes place in the domicile of the avian definitive host. Following a blood meal, eggs are laid in the nests of birds or in the cracks and crevices in the wall of poultry houses. Up to seven eggs are laid at a time. At outdoor summer temperatures, the eggs hatch in two to three days, releasing the six-legged larvae, which do not feed. The larvae molt to the eight-legged protonymph stage, which will feed on the host's blood. After another one to two days, they develop into deutonymphs. These feed on blood and after another one to two days, then molt to adults. Under optimum conditions, the entire life cycle can be completed in seven days to five months (Grant, 1989). Under experimental conditions, the adult mites have been able to live for 34 weeks without a blood meal.
CLINICAL PRESENTATION AND PATHOGENESIS: Mites often infest wild birds nesting in the eaves of homes. These mites may enter open windows and infest the people or their pets living there. Most cases associated with pets are found in cats or dogs that have access to or live in recently converted poultry houses. Clinical signs include erythema and papulocrustous eruptions which are intensely pruritic. These lesions are often distributed over the back and extremities (Muller et al., 1983).
DIAGNOSIS: Infestations with Dermanyssusgallinae are often diagnosed by a history of contact with poultry houses or by close examination of environmental conditions (eg., eaves, air conditioners, open windows, etc.) associated with a building that birds use for nesting (Muller et al., 1983, Regan et al., 1987). The mites are visible to the naked eye, particularly if they have fed recently on blood, and as a result, they are red in color. Diagnosis is by finding the mites on skin scraping (Muller et al., 1983). When suspected mites are removed from an infested host, cleared in lactophenol and examined under a compound microscope, they will demonstrate the key morphologic features necessary for identification: size, number of legs, the very prominent dorsal shield with its truncated posterior end, and the ventral anal plate with the anus located on the posterior aspect.
TREATMENT:Dermanyssusgallinae is susceptible to most insecticidal preparations; almost any bath, dip, or spray will eliminate the mites (Muller et al., 1983).
EPIZOOTIOLOGY: Most cases of Dermanyssusgallinae in the cat occur when there is an association of cats with poultry houses. The possibility of spread from pigeons or pigeon nests around houses also exists (Muller et al., 1983).
HAZARDS TO OTHER ANIMALS: Ramsay and Mason (1975) reported a case in a dog which was so infested that the numbers of mites crawling through the haircoat resembled the dandruff produced in infestations with Cheyletiella species.
HAZARDS TO HUMANS: When pigeons nest near human dwellings, these mites may attack humans. Dermanyssusgallinae is only one of six mites that may produce fowl mite dermatitis in humans. In the absence of an avian host, this mite will attack humans, producing a pruritic, macular, papular, vesicular, or urticarial rash. It may also serve as a potential vector for the viruses of eastern and western equine encephalomyelitis and Saint Louis encephalitis (Regan, 1987). Laboratory and epidemiologic studies suggest that these mites play no important role in the maintenance of these pathogens. Field isolation probably means that the mite has recently fed on viremic birds (Harwood and James, 1979).
CONTROL/PREVENTION: Treatment of the infested premises that serve as the source of infestation should be accomplished to prevent reinfestation (Muller et al., 1983).
Grant DI. 1985. Notes on parasitic skin disease in the dog and cat. Br Vet J 141:447-462.
Grant DI. 1989. Parasitic diseases in cats. J Sm Anim Prac 30:250-254.
Harwood RF, James MT. 1979. Helminths, Arthropods, and Protozoa of Domesticated Animals. 7th edition. Macmillan. New York. P. 347.
Ramsay GW and Mason PC. 1975. Chicken mite (D. gallinae) infesting a dog. N Zealand Vet J 62:701.
Regan AM, Metersky ML, and Craven DE. 1987. Nosocomial dermatitis and pruritus caused by pigeon mite infestation. Arch Intern Med 147:2185-2187
Muller GH, Kirk, RW, and Scott, DW. 1983. Small Animal Dermatology. 3rd edition. W.B. Saunders. Philadelphia. P. 317.
Figure 5-19. Dermanyssusgallinae. Adult mite, notice the long, narrow, chelicerae.