PCR amplification and DNA sequence identification of an unusual morphological form of Demodex cati in a cat.

BACKGROUND Molecular characterization of Demodex mites is being used to identify mite species in dogs. This technique is now being applied to cat Demodex species, allowing for better characterization of the mites. HYPOTHESIS/OBJECTIVES Molecular diagnostics will clarify the existence of diverse Demodex mites identified morphologically. ANIMALS A cat with generalized demodicosis secondary to chronic steroid treatment for erythroid dysplasia. METHODS Skin scrapings demonstrated large numbers of follicular mites consistent with Demodex cati as well as a morphologically different Demodex mite with a blunted abdomen. The 16S rRNA DNA was amplified by PCR, sequenced and compared with available Demodex sequences, including Demodex cati, Demodex gatoi and an unnamed Demodex sp. RESULTS A single PCR product was obtained, the DNA sequence of which was an exact match with D. cati. CONCLUSIONS AND CLINICAL IMPORTANCE The shorter unnamed mite was not a different species in this case, but a different morphological form of D. cati. This report demonstrates the utility of molecular diagnostics to clarify the identity of mites that differ morphologically.