Submitted to: Journal of Zoo and Wildlife Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2006
Publication Date: December 1, 2006
Citation: Fayer, R., Santin, M., Trout, J.M., Destefano, S., Koenen, K., Kaur, T. 2006. Prevalence of Microsporidia, Cryptosporidium, and Giardia in beavers (Castor canadensis) in Massachusetts. Journal of Zoo and Wildlife Medicine. 37:492-497.
Interpretive Summary: Microsporidia, Giardia and Cryptosporidium are protozoan parasites that that are transmitted through contaminated drinking water to humans resulting primarily in intestinal infections characterized by diarrheal disease. Hikers and backpackers have long associated intestinal illness with the presence of beavers in otherwise pristine waters. When diarrheal illness resulted from drinking that water, the illness was referred to as "beaver fever." The present study was undertaken using molecular methods to precisely characterize the protozoan parasites excreted by beavers and thereby determine if these were the same parasites that infect humans and livestock or if they are parasites that only appear similar to those infecting humans and livestock when examined microscopically. Microsporidia was not found. Cryptosporidium was found but the species could not be identified. Giardia was found and was determined to be a type infectious for humans but not for livestock.
Feces from 62 beavers (Castor canadensis) in Massachusetts were examined by fluorescence microscopy (IFA) and polymerase chain reaction (PCR) for Microsporidia, Cryptosporidium, and Giardia. PCR-positive specimens were further examined by gene sequencing. Parasites were detected in 6.4% of the beavers. All were sub-adults and kits. Microsporidia were not detected. Giardia was detected by IFA from 4 beavers; Cryptosporidium was also detected by IFA from 2 of these beavers. However, gene sequence data for the ssrRNA gene from the Cryptosporidium positive beavers were not conclusive in identifying the species. Nucleotide sequences of the TPI, ssrRNA, and '-giardin genes for Giardia indicated that the beavers were excreting Giardia duodenalis Assemblage B, the zoonotic genotype representing a potential source of waterborne Giardia cysts.