Crusted scabies causing skin disease in four cats

Abstract

Four new cases of sarcoptic mange in cats are described. Two cats resided in areas known to be frequented by foxes, another cohabited with a dog recently diagnosed with sarcoptic mange, while the final cat lived with a mixed breed dog that had been treated for sarcoptic mange 7 months previously. Three cases were diagnosed on the basis of characteristic mite size and morphology in skin scraping from representative lesions, situated on the head (two cases) or head and distal hind limbs (one case). Mites were highly mobile and abundant in all instances, and easily detected also in skin biopsy specimens procured from two cases. Eosinophilic inflammation, hyperkeratosis and parakeratosis were prominent in the tissue sections. In the remaining case, the diagnosis was presumptive, based on characteristic lesions, cohabitation with a canine scabies patient and positive response to scabicide therapy. Pruritus was not a prominent clinical feature in any patient and was considered to be absent in three of the four cases. Lesions in three cats with long-standing disease were reminiscent of crusted scabies (synonym: Norwegian scabies, parakeratotic scabies) as seen in human patients. In three cases, in-contact human carriers developed itchy cutaneous papular lesions. Two cases responded promptly to therapy with systemic avermectin drugs, while one responded to topical treatment with lime sulphur and the remaining cat received both a lime sulphur rinse and ivermectin. Sarcoptic mange should be considered in the differential diagnosis of cats with non-pruritic crusting skin diseases, especially when there is contact with foxes or dogs, and when owners have itchy papular lesions.