A ZOONOTIC GENOTYPE OF ENTEROCYTOZOON BIENEUSI IN HORSES

This is the first report of Enterocytozoon bieneusi in an equid species. Feces from 195 horses from 4 locations in Colombia were examined for E. bieneusi by polymerase chain reaction. Of these, 21 horses (10.8%) were found positive for E. bieneusi. The prevalence of E. bieneusi in horses ,1 yr of age was significantly higher (23.7%) than in horses .1 yr of age (2.5%). No significant differences in prevalence were observed between male (13.7%) and female horses (9%). Sequencing of the internal transcribed spacer region of the SSUrRNA locus identified 3 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 4 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 for humans. Microsporidia are obligate, intracellular parasites consisting of more than 1,200 species in 143 genera. They infect a wide range of invertebrate and vertebrate hosts. Of 14 species in 6 genera reported to infect humans, Enterocytozoon bieneusi is recognized as the most common microsporidian species (Didier and Weiss, 2006). Enterocytozoon bieneusi has been also detected in a broad range of animals, raising the concern that animals could be a potential source of infection for humans. Considerable genetic diversity within E. bieneusi has been observed, with more than 80 genotypes of the parasite differentiated based on polymorphisms of the internal transcribed spacer (ITS) sequence of the rRNA gene; some genotypes appear to be host specific, while others have a broad host range, supporting the likelihood of zoonotic transmission (Santin and Fayer, 2009). The only published reports of testing for microsporidia in equids were of horses and donkeys in Switzerland and Spain, which were found to be negative for the parasite (Breitenmoser et al., 1999; Lores et al., 2002). The present study was conducted to examine horses from a different geographic location, Colombia, South America, for the presence of E. bieneusi in their feces.