Some diseases and parasites affecting cottontail rabbits in Virginia

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Virginia Polytechnic Institute and State University

A serologic survey at Fort Pickett, Virginia was undertaken to determine if tularemia could be a factor in the continued low hunter harvest of cottontail rabbits. Between December 1976 and February 1978, ninety serum samples were collected from 11 species of mammals and 1 avian species, and tested for antibodies against Francisella tularensis. Evidence of infection was found in 5 raccoons, 3 opossums, 1 striped skunk, 1 Norway rat, 1 chipmunk, 1 white-tailed deer, and 1 bobwhite quail. This indicated that tularemia was present at Fort Pickett in a number of species and could be responsible for the low numbers of cottontails present.

As the result of an epizootic of cerebrospinal nematodiasis among rabbits caused by Baylisascaris procyonis, a survey of the presence of B. procyonis in its definitive host was undertaken. Between December 1976 and February 1978, 72 raccoons from 11 counties were examined. B. procyonis was found in raccoons from Augusta, Carroll, and Montgomery Counties. It was not found in any raccoons collected from the 6 counties east of the Blue Ridge. This indicates that B. procyonis may only be a cottontail regulatory factor west of the Blue Ridge Mountains.

A final phase of the study was to determine the effects of parasitism and nutritive restriction. In a 2x2 factorial design experiment 19 cottontails were placed on an ad libitum or 70 percent ad libitum diet and treated with AtgardR, an anthelmintic, or untreated control. It was found that Trichostrongylus spp. were the only parasites significantly affected by drug treatment. The animals on the 70 percent ad libitum diet had lower final body weights, carcass weights, liver weights, tibia and femur marrow fat levels, and lower abdominal fat indices. It was concluded that the parasite loads were too light to significantly affect the host.