Parasites of Cottontail Rabbits on the San Joaquin Experimental Range, California

Abstract

From August 1941 to March 1942, 44 cottontail rabbits (Sylvilagus audubonii vallicola) were examined for parasites at the Los Angeles Wildlife Disease Research Station of the U. S. Fish and Wildlife Service, in part of a cooperative study of the causes of wildlife fluctuations in western United States by the Fish and Wildlife Service and the Forest Service. The rabbits were trapped alive by Henry S. Fitch and Lowell Adams on the San Joaquin Experimental Range, in the foothills at the eastern edge of the San Joaquin Valley near O'Neals, Madera County, California. Most of the rabbits were killed and autopsied shortly after being received, but 20 were kept for periods up to two months for experimental purposes. Fecal samples from the latter animals were examined periodically and 10 were inoculated with Eimeria stiedae from domestic rabbits. Passed feces were examined by the zinc sulfate centrifugation technique described by Faust, et al. (1939). At autopsy, the body cavities were opened and search made for cycticerci of Taenia pisiformis. Blood from the heart, liver, and lung was mixed with physiological saline and examined under low magnification. The liver and contents of the gall bladder were searched for Eimeria stiedae. The alimentary canal was opened and each organ examined separately. Smears in physiological saline from the contents of each area and scrapings of the mucosa were examined microscopically. The contents were then washed with tap water in both black and white enamel pans and any parasites were removed to physiological saline for further washing before being killed and preserved. Cultures of coccidia were prepared in 2 per cent potassium dichromate. Nematodes were killed in hot 70 per cent alcohol and later cleared in phenol-alcohol for identification. Cestodes were killed in a hot mixture of alcohol, formalin, and acetic acid. Identification of cestodes was made