A laboratory cat experimentally infected with and positive for feline immunodeficiency virus had acute onset of severe pruritus.The cat had patchy areas of hair loss and crusting on the neck, ears, and dorsum. In addition, it had marked scaling and an erythematous papular eruption. Superficial and deep skin scrapings revealed both Demodex cati and D gatoi. The mites were also found on ear swab cytology of ceruminous debris. Skin biopsies revealed a superficial perivascular and perifollicular inflammatory infiltrate consisting of histiocytes, lymphocytes, and plasma cells. Demodex mites were found with the superficial keratin and in the intrafollicular areas.

COMMENTARY: Feline demodicosis has been reported as "rare," and many textbooks list the South as being a "hotbed" of feline demodicosis.This has not been my experience.This disease is commonly overlooked and is underdiagnosed. Most clinicians are well aware of D cati and that it is common in cats with systemic illness.The workup of cats with pruritic ear disease should include both a cutaneous cytologic evaluation of the debris and a mineral oil smear.The latter is often not done in adult cats unless Otodectes is suspected.The most common presentation of D cati is a young, newly acquired, pruritic cat. D cati can be difficult to find because it lives superficially in the keratin. Hair plucking (the mite is commonly seen on the proximal one third of the hair) and widespread superficial skin scraping are recommended. My first treatment of choice for D cati is lime sulfur every 3 to 7 days for 4 to 8 weeks. Marked relief often occurs within the first few topical treatments. I have also used topical lime sulfur with concurrent ivermectin.

Deep and superficial skin scrapings from a feline immunodeficiency virus positive cat. Neel JA,Tarigo J,Tater KC, Brindem CB. VET CLIN PATHOL 36:101-104, 2007. Photo courtesy Karen Moriello