Date of this Version
The Prairie Naturalist 43(1/2):56–58; 2011
White-tailed jackrabbits (Lepus townsendii) are common on the prairie, and an important species in prairie food webs (Lim 1987). Although it has been suggested that jackrabbits have cyclic populations (Donoho 1972, Gross et al. 1974, Anderson and Shumar 1986), there is concern that a general downward trend exists in populations in the Northern Great Plains (Feldhamer et al. 2003). Disease incidence in white-tailed jackrabbits is poorly known (Feldhamer et al. 2003), but may be an important factor in population changes. Tularemia, a disease caused by bacteria (Francisella tularensis), occurs throughout the Northern Hemisphere and can affect many mammals including hares, rabbits and rodents (Feldhamer et al. 2003). As part of a larger study, our objective was to determine the incidence of tularemia in white-tailed jackrabbits in South Dakota. We collected livers from 314 white-tailed jackrabbits throughout 44 counties in South Dakota from June 2004 to August 2005. We examined all livers for any lesions and evidence of infection, and only 16 abnormal livers were found. We submitted these livers to the Animal Disease Research and Diagnostic Laboratory at South Dakota State University for microscopic and bacterial examinations.
We detected no evidence of bacterial infection (including F. tularensis) in 298 examined livers or 16 abnormal livers. However, 4 of the livers were infected with Calodium hepaticum, a nematode parasite primarily detected in rodents and in some lagomorphs (Anderson 2000). The remaining livers had lesions characterized by hemorrhage, inflammation, or necrosis with undetermined causes.