Pathological and physiological relationships of parasitic disease in a select cottontail rabbit population

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Virginia Polytechnic Institute and State University


Forty-seven cottontail rabbits, Sylvilagu floridanus, were used in a 2 x 2 factorial experiment to determine the effects of parasite reduction on host physiology. Rabbits were treated with insecticide-generating collars (Sergeant's Sentry Dog Collar) and a broad spectrum antihelminth drug (Tramisol, American Cyanamid) to reduce parasite burdens. Rabbits were confined in 4 one-quarter acre outdoor enclosures during the treatment period. Thirty-one rabbits were recovered at the end of the treatment period. Data from these rabbits and 10 wild rabbits were analyzed. Treatment with insecticide-generating collars resulted in complete elimination of ectoparasites from rabbits which received this treatment. The two groups of rabbits which received treatment with the drug Tramisol had a significant reduction (p<.05) in the number of nematode parasites recovered. Reduction of nematode numbers was accompanied by significant changes in the generalized blood picture. Total serum protein, serum globulin fraction, lymphocyte percentage, and monocyte percentage were significantly (p<.05) reduced and neutrophil percentage was significantly increased (p<.05) in drug treated groups. A simple correlation analysis was conducted between parasite burdens and select physiological measurements. A highly significant (p<.001) correlation of 0.57 was found between parasite burden and basophil percentage. A highly significant (p<.01) correlation of -0.57 was found between eye lens weights and the presence of Cuterebra maggots. A significant (p<.05) correlation of 0.33 was found between serum corticoid levels and numbers of ticks recovered. These results indicate that parasites may, under some conditions, operate as a limiting factor to cottontail rabbit populations.