Identification of Giardia duodenalis and Enterocytozoon bieneusi in an epizoological investigation of a laboratory colony of prairie dogs, Cynomys ludovicianus

Since 2005, black-tailed prairie dogs (Cynomys ludovicianus) have been collected for use as research animals from field sites in Kansas, Colorado, and Texas. In January of 2012, Giardia trophozoites were identified by histology, thin-section electron microscopy, and immunofluorescent staining in the lumen of the small intestine and colon of a prairie dog euthanized because of extreme weight loss. With giardiasis suspected as the cause of weight loss, a survey of Giardia duodenalis in the laboratory colony of prairie dogs was initiated. Direct immunofluorescent testing of feces revealed active shedding of Giardia cysts in 40% (n = 60) of animals held in the vivarium. All tested fecal samples (n = 29) from animals in another holding facility where the index case originated were PCR positive for G. duodenalis with assemblages A and B identified from sequencing triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh), and β-giardin (bg) genes. Both assemblages are considered zoonotic, thus the parasites in prairie dogs are potential human pathogens and indicate prairie dogs as a possible wildlife reservoir or the victims of pathogen spill-over. Molecular testing for other protozoan gastrointestinal parasites revealed no Cryptosporidium infections but identified a host-adapted Enterocytozoon bieneusi genotype group.