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| Fig. 34.7 Cheyletiella mite resembles scabies in size but is identified by the hooklike palps anteriorly. |
Cheyletiella species are free-living, nonburrowing, ectoparasitic mites of dogs, cats, and rabbits. The mite is about the same size as the scabies mite but can be easily differentiated by the presence of pincher-like palps tipped with strong claws used for grasping fur (Fig. 34-7). The eggs are attached to the hair shaft of the animal. The most common sources of the infestation are long-haired cats and new puppies. Animals are often asymptomatic, but a white dandruff-like scale on their backs and necks is often seen on close examination. Small, yellow-white scales which are the mites themselves, are also seen, and hence the disease is called “walking dandruff.”
Infested patients complain of pruritic eruptions, which occur most commonly in the sites that correspond to a dog sitting on the patient’s lap, volar forearms, abdomen, and anterior thighs. The red papules may develop vesicles, pustules, and even necrosis, and the severity and the extent of the rash depends on the duration of contact with the pet. Diagnosis is made by microscopic examination of the pet. Treatment is directed toward the pet, the pet contacts, and the environment. The patient requires symptomatic care with antiitch medications.
Cheyletiella is common, and the infestation often goes undiagnosed or unrecognized.
Canine scabies is rarely asymptomatic. Usually the symptoms are severe: redness, scaling, pruritic on the face, margins of the ears and distal extremities. Puppies are always symptomatic. In man, the mite can penetrate clothing and symptoms are severe and onset may occur within an hour. The rash resembles the distribution of
Cheyletiella—chest, anterior arms, and thighs—but the inverse distribution of human scabies. The face is frequently affected, but hands and genitalia are not affected. The itch is nocturnal and increases with warmth. No burrows are seen. Lindane does not work for pets, so ivermectin and dips are used on all the animals.
Other animals with mite infestations that affect humans include the following:
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Ornithonyssus sylviarum (northern fowl mite): Chickens
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Ornithonyssus bacoti (tropical rat mite): Rats
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Ornithonyssus bursa (tropical fowl mite): Sparrows
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Dermanyssus gallinae (poultry mite): Chickens
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Feline scabies: Cats
Lee B:
Cheyletiella: report of 14 cases,
Cutis 47:11, 1992.
