Identification and characterization of Eimeria spp. in western north American Bison (Bison bison) herds and potential risk of cross-species transmission

The American bison (Bison bison) is an iconic native wildlife species of the Great Plains of North America. Recently, farmed bison have also gained importance to the livestock industry across the United States and Canada. One of the common diseases in young bison is coccidiosis, a diarrheal disease caused by protozoa that can result in significant morbidity. The goal of the present study was to investigate occurrence and identity of bison coccidia of the genus Eimeria in both farmed and free-ranging bison with focus on potential Eimeria species transmissibility between bison and cattle. Individual bison (up to one year of age) were sampled across Wyoming, Colorado, Nebraska, and South Dakota on six bison ranches (n = 137) and in two free-range herds (n = 70). Eimeria populations were assessed by fecal analyses. Morphological identification revealed presence of oocysts consistent with Eimeria (E.) bovis, E. zuernii, E. ellipsoidalis, E. cylindrica, E. alabamensis, E. auburnensis, E. canadensis, E. pellita, E. subspherica, and E. bukidnonensis, all of which are described in cattle. Additional Eimeria species specific ITS1 sequencing data along with generated phylogenetic maximum likelihood trees suggest that Eimeria species from cattle, namely E. bovis, E. zuernii, E. alabamensis, E. cylindrica, E. brasiliensis, E. ellipsoidalis, and E. wyomingensis, are genetically consistent with the detected bison coccidia. In conclusion, the study results indicate that bison harbor a variety of Eimeria species and bison Eimeria species appear to be transmissible between different bovine species such as bison and cattle.