Morphologic and Molecular Characterization of a Demodex (Acari: Demodicidae) Species from White-Tailed Deer (Odocoileus virginianus)

Demodex mites, although usually nonpathogenic, can cause a wide range of dermatological lesions ranging from mild skin irritation and alopecia to severe furunculosis. Recently, a case of demodicosis from a white-tailed deer (Odocoileus virginianus) revealed a Demodex species morphologically distinct from Demodex odocoilei. All life cycle stages were considerably larger than D. odocoilei and although similar in size to D. kutzeri and D. acutipes from European cervids, numerous morphometrics distinguished the four species. Adult males and females were and ？μm in length, respectively. Ova, larva, and nymphs measured , , and ？μm in length, respectively. For phylogenetic analyses, a portion of the 18S rRNA gene was amplified and sequenced from samples of the WTD Demodex sp., two Demodex samples from domestic dogs, and Demodex ursi from a black bear. Phylogenetic analyses indicated that the WTD Demodex was most similar to D. musculi from laboratory mice. A partial sequence from D. ursi was identical to the WTD Demodex sequence; however, these two species can be differentiated morphologically. This paper describes a second Demodex species from white-tailed deer and indicates that 18S rRNA is useful for phylogenetic analysis of most Demodex species, but two morphologically distinct species had identical partial sequences. Additional gene targets should be investigated for phylogenetic and parasite-host association studies. 1. Introduction Mites of the genus Demodex are commonly found in the hair follicles and sebaceous glands of most mammals. In general, Demodex are considered to be host-species specific and some hosts can be infested with two or more distinct species (e.g., D. canis, D. injai, an undescribed short form Demodex sp. in dogs, D. brevis and D. folliculorum in humans, D. odocoilei in white-tailed deer (Odocoileus virginianus), and D. bovis in cattle) [1–5]. In general, Demodex infestations can vary widely in clinical presentation (from asymptomatic animals to cases with variable extends of alopecia, varying degrees of thickening of the skin, to cutaneous nodular lesions and severe dermatitis/furunculosis). In small animals, some animals have concurrent immunosuppression; however, it is unclear what role immunosuppression plays in generalized clinical demodicosis. In addition, some individuals or species, especially cervids in Europe, as well as cattle, develop a nodular demodicosis [3, 6]. In a longitudinal study of cattle, these nodules waxed and waned both in number and size over time [6]. A Demodex sp. was first detected in a white-tailed deer