Coccidian parasites (Apicomplexa) from snakes in the southcentral and southwestern United States: new host and geographic records.

Four hundred thirty-five leptotyphlopid, colubrid, elapid, and viperid snakes were collected from various localities in Arkansas, New Mexico, Oklahoma, and Texas, and their feces were examined for coccidian parasites. Of these, 131 (30%) were passing oocysts or sporocysts of at least 1 coccidian; 88 (67%) of the infected snakes had only 1 species of coccidian when they were examined. Aquatic and semiaquatic snakes accounted for 48% of the infections, whereas strictly terrestrial snakes comprised the other 52%. There was more than a 2-fold difference in prevalence among these 2 groups as 63 of 129 (49%) of the aquatic and semiaquatic snakes versus 68 of 306 (22%) of the terrestrial snakes harbored coccidia. Most terrestrial snakes were infected by species of Caryospora and Sarcocystis that are either facultatively or obligatorily heteroxenous. The aquatic and semiaquatic species most often harbored eimerians. Attempts to transmit some of the Sarcocystis spp. experimentally from Crotalus atrox to Mus musculus, Peromyscus leucopus, Peromyscus maniculatus, or Microtus ochrogaster were unsuccessful. This report documents 27 new host and several distributional records for coccidians from snakes in the southcentral and southwestern United States.