Deep and superficial skin scrapings from a feline immunodeficiency virus–positive cat

Abstract

An 8-year-old, neutered male, domestic shorthair cat housed at the North Carolina State University, College of Veterinary Medicine, Laboratory Animal Research facility as part of a research colony was examined because of mulifocal skin lesions. The lesions consisted of patchy alopecia with mild crusting of the periauricular region, neck, and dorsum; periauricular excoriations; marked dorsal seborrhea and scaling; and generalized erythematous papules. A moderate amount of ceruminous exudate was present in both ear canals. Results of testing for feline immunodeficiency virus (FIV) were positive. An ear swab specimen and superficial and deep skin scrapings were obtained, mounted with oil on glass slides, and coverslipped for microscopic examination. Two populations of mites were observed: a large population of slender, long (approximately 200 microm), adult mites with long, tapering abdomens that comprised two-thirds of the total body length; and a smaller population of more translucent and shorter mites (approximately 100 microm) with wide, blunt abdomens that had prominent transverse ridges. The interpretation was demodicosis, with Demodex cati and D gatoi co-infection. Histologic sections of biopsies from skin lesions on the neck, dorsum, and periauricular area contained a mild perivascular and perifollicular inflammatory infiltrate composed predominantly of histiocytes, lymphocytes, and plasma cells. Diffusely within the follicular lumina and occasionally within the superficial keratin, a myriad of Demodex organisms were observed. Intrafollicular mites were compatible in appearance with D cati whereas those in the corneal layer were suggestive of D gatoi. Demodicosis is an uncommon disease of cats, and rare cases of dual infection have been documented, occasionally in FIV-infected cats. The dual infection emphasizes the importance of doing both superficial and deep skin scrapings and of recognizing the unique microscopic features of different Demodex mites.