Helminths of the Prairie Rattlesnake, Crotalus viridis viridis (Serpentes: Viperidae), from Western South Dakota

One hundred prairie rattlesnakes, Crotalus viridis viridis, from western South Dakota were examined for evidence of helminth parasites. Twenty-one percent were infected with 1 of 6 parasite species. The following species were recovered: Manodistomwn sp., Mesocestoides sp., Physaloptera sp., 2 different species of oligacanthorhynchid acanthocephala, and an unidentified species of acanthocephalan. The occurrences of oligacanthorhynchid acanthocephala and Manodistomum sp. in C. v. viridis represent new host and locality records. A natural infection of Mesocestoides sp. tetrathyridia is documented in this host for the first time.