Background: Microsporidia infections occur in all invertebrate and vertebrate hosts. The most common microsporidia infecting humans and animals are Enterocytozoon bieneusi. This study aimed to characterize the zoonotic isolates of E. bieneusi using a molecular method among the slaughtered cattle in Tehran.

Materials and Methods: In this descriptive study, 126 fecal samples from slaughtered cattle in Tehran were analyzed for Enterocytozoon bieneusi. A transcribed spacer region (500 bp) for rRNA gene of E. bieneusi was amplified using a nested PCR technique. For genotyping, positive samples were sequenced and the phylogenetic tree was reconstructed to determine the relationship between the isolates from human, animal and zoonotic isolates.

Results: Nineteen out of 126 E. bieneusi PCR-positive samples were sequenced. A high degree of genetic polymorphism, represented by four genotypes (IREb4, IREb5, D, M), was found among the E. bieneusi isolated from cattle. In this study, the most common genotypes were D (38.6%), M and IREb4 (26.3%), respectively followed by IREb5 (10.5%) in the next stage. In phylogenetic analysis, 89.5 percent of the isolates (D، IREb4 و IREB5) formed a distinct cluster consisting of genotypes from humans and other domestic animals, but one genotype clustered as E. bieneusi genotypes taken from cattle and pig.

Conclusion: Only some E. bieneusi isolates taken from cattle may be of public health importance. However, further studies should be conducted on cattle and other hosts to determine the role of animals in the transmission of infection to human.