Zoonotic potential of Enterocytozoon bieneusi

Abstract

The reservoirs and the modes of transmission of the most frequent microsporidial species in humans, Enterocytozoon bieneusi, are still unknown. We have examined fecal samples of 26 humans and 350 animals from 37 species to find 18 samples containing this parasite from humans, cats, pigs, cattle, and a llama. Genotypic characterization of the internal transcribed spacer of the rRNA gene resulted in 14 different genotypes, 6 of them previously undescribed. Phylogenetic analysis revealed the lack of a transmission barrier between E. bieneusi from humans and animals (cats, pigs, and cattle). Thus, E. bieneusi appears to be a zoonotic pathogen.

FIG. 1

Phylogenetic trees based on comparisons of the E. bieneusi ITS sequences from the genotypes given in Table 1. The dendrograms were constructed using the maximum-likelihood method, choosing the tree with the lowest natural logarithm likelihood score (ln likelihood = −822) (A); distance matrix (neighbor-joining) analysis (B); and maximum-parsimony algorithms employing bootstrapping of more than 1,000 replicates each (C). Bootstrap values given are percentages, and each value indicates how often the group of genotypes indicated to the right of the respective fork occurred among the 1,000 replicates. The ITS sequence of a taxonomically unresolved species related to E. bieneusi (GenBank accession number AF059610) was used as the outgroup.