The University of Georgia College of Veterinary Medicine

Georgia Veterinary Scholars Program

GVSP Summer 2006 Scholars

Georgia Veterinary Scholar	Faculty Mentor

Sarah Clay University of Georgia Class of 2009	Dr. Micheala Austel

Characterization of Demodex from White-Tailed Deer (Odocoileus virginianus)

Sarah E. Clay*1, Michael J. Yabsley1,2, Samantha E.J. Gibbs1, Michaela Austel3
1Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, 2Warnell School of Forestry and Natural Resources and 3Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA.

Mites in the genus Demodex (Order Acariformes, Superfamily Chelyetoidea) are commonly found in the hair follicles and sebaceous glands of many mammals. Although usually nonpathogenic, Demodex can cause alopecia and dermatitis. The objectives of this study were to 1) review the pathology of 13 demodicosis cases in white-tailed deer and 2) characterize and describe a new species of Demodex that can cause disease in white-tailed deer. The 13 deer with demodicosis presented with varying degrees of alopecia and some had few to numerous small dermal nodules with intralesional caseous material. Histopathologic lesions varied widely. Some deer had only a limited reaction to the mites while others developed giant cystic structures that severely distended the hair follicles. A few cases had large granulomas and dermal fibrosis associated with mites. Microscopic examination of mites from one case revealed a Demodex morphologically distinct from Demodex odocoilei, the only Demodex described from white-tailed deer. This new Demodex was approximately 70% larger than D. odocoilei. Currently, there is no genetic information available to distinguish between species of Demodex or to conduct phylogenetic analyses with other mites. PCR protocols previously designed to amplify the 18S rRNA gene from a wide range of mites and ticks were tested for applicability amplifying Demodex DNA. Several successfully amplified fragments were sequenced. Overlapping segments were aligned and subjected to phylogenetic analyses which showed that Demodex mites are most closely related to an unidentified eukaryote from a human ear canal and another member of the superfamily Chelyetoidea (Neochelacheles messersmithi). This group formed a sister clade to mites in the Order Parasitiformes. This is the first molecular characterization of Demodex which can potentially be used to develop Demodex-specific PCR protocols.