Morphological variability of Demodex cati in a feline immunodeficiency virus-positive cat.

CASE DESCRIPTION A 17-year-old FIV-positive cat was evaluated because of weight loss during the preceding few months. The cat had a weight loss of 0.5 kg (1.1 lb) during the last month. Because of its FIV-positive status, the cat was confined indoors. CLINICAL FINDINGS A large nonpruritic area of alopecia with hyperpigmentation and comedones was present on the right lateral aspect of the neck. The chin had diffuse alopecia and comedones. Mild alopecia was present on the dorsal aspect of the muzzle. Trichography and microscopic examination of acetate tape imprint preparations and skin scrapings revealed a very morphologically heterogeneous population of Demodex mites. Micrometry of adult mites revealed a broad range of body lengths (92.68 to 245.94 μm), which suggested that as many as 3 Demodex spp might be present in the skin lesions of this cat. TREATMENT AND OUTCOME Owing to its concurrent disease, no treatment was initiated for the demodicosis, and the cat died spontaneously 14 days after the evaluation. Sequence analysis of the 16S rRNA gene of collected mites was performed. Analysis revealed that the 16S rRNA gene sequence of collected mites appeared 100% identical to the Demodex cati 16S rRNA gene sequence deposited in GenBank (JX193759). A similarity of 79.2% and 74.4% was found when the 16S rRNA gene sequence of collected mites was compared with that of Demodex gatoi (JX981921) and Demodex felis (KF052995), respectively. CLINICAL RELEVANCE Demodicosis in cats is often associated with underlying disease. In cats, FIV infection may lead to an altered immune response and induce species polymorphism of Demodex mites.