Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2009
Publication Date: 1/1/2010
Citation: Santin, M., Cortes Vecino, J.A., Fayer, R. 2010. A zoonotic genotype of Enterocytozoon bieneusi in horses. Journal of Parasitology. 96(1):157-161.
Interpretive Summary: Microsporidia are tiny infectious agents of humans and animals. The most prevalent species infecting humans, Enterocytozoon bieneusi, has recently been detected by ARS scientists and collaborators in wild fur-bearing animals and cattle in North America. In the present study molecular tools were used to test horses for the presence of this organism. Fecal specimens were obtained from 195 horses in four geographically separated areas in Colombia, South America. Enterocytozoon bieneusi was found on farms in three of the four areas. Nearly one quarter of the horses under one year of age were infected whereas 2.5 percent of horses older than one year of age were infected. Three distinctly different genetic types (genotypes) were found. Two have never been reported before and, therefore are thought to be unique to horses. The third type has been found in humans and a variety of wild and domesticated animals and is therefore considered zoonotic, with potential to infect humans. This study is the first to identify this group of parasites in horses.
Technical Abstract: This is the first report of Enterocytozoon bieneusi in an equid species. Feces from 195 horses from four locations in Colombia were examined for E. bieneusi by PCR. Of these, 21 horses (10.8 percent) were found positive for E. bieneusi. The prevalence of E. bieneusi in horses <1 yr of age was significantly higher (23.7 percent) than in horses >1 yr of age (2.5 percent). No significant differences in prevalence were observed between male (13.7 percent) and female horses (9 percent). Sequencing of the ITS region of the SSUrRNA locus identified three genotypes. Two genotypes appear to be unique to horses and were named Horse 1 and Horse 2. A third genotype, identified as genotype D, was detected in four horses. This genotype, previously reported to infect humans, beaver, cattle, dogs, falcons, foxes, macaques, muskrats, pigs, and raccoons, is the most ubiquitous of the E. bieneusi zoonotic genotypes. Our findings indicate that E. bieneusi from horses can be a potential source of infection from humans.