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Grand Teton National Park Report

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The Objective of this study using free-ranging elk and a related study using captive elk was to test the efficacy and safety of a new parasiticide, ivermectin, for the control of psoroptic scabies in elk. Scabies is a disease caused by mites of the genus Psoroptes which pierce the epidermis of the host and feed on lymph. Infected areas become heavily encrusted with exudate, and scabs and hair are eventually shed (Tarry, 1974). Scabies results in hair, fluid, and heat loss; ear canal occlusion; secondary infections; decreased weight gain; and mortality in domestic and wild animals (Tarry 1974, Colwell and Dunlap 1975, Lange et al. 1980, Fisher and Wright 1981). Scabies (Psoroptes cervinus) has long been known to occur in elk ( Cervus elaphus) of the Jackson Hole herd (Murie, 1951; Honess, 1982). Severe infestation is most common in mature bulls and it is a major cause of winter mortality in this sex and age class (Smith 1985). Effective treatment of scabies in wild animals has not been practical. Conventional techniques used on domestic animals involve dipping in antiparasitic chemicals. A relatively new parasiticide, ivermectin (22, 23 dihydroavermectin B1), has shown promise for treating domestic and wild animals (Egerton, et al., 1980). Ivermectin is a broad spectrum antiparasitic agent which acts upon nematodes and arthropods and has a wide range between therapeutic and toxic dose in most animals (Campbell and Benz, 1984). Successful completion of this project will likely demonstrate a technique to save the lives of scabies infested bull elk; more importantly, it may demonstrate a method for controlling scabies in elk.