Zoonotic and Potentially Host-Adapted Enterocytozoon bieneusi Genotypes in Sheep and Cattle in Northeast China and an Increasing Concern about the Zoonotic Importance of Previously Considered Ruminant-Adapted Genotypes.

This study investigated fecal specimens from 489 sheep and 537 cattle in multiple cities in northeast China for the prevalence and genetic characteristics of Enterocytozoon bieneusi by PCR and sequencing of the ribosomal internal transcribed spacer. Sixty-eight sheep specimens (13.9%) and 32 cattle specimens (6.0%) were positive for E. bieneusi. Sequence polymorphisms enabled the identification of 9 known genotypes (BEB4, BEB6, CM7, CS-4, EbpC, G, I, J, and OEB1) and 11 new genotypes (NESH1 to NESH6 and NECA1 to NECA5). The genotypes formed two genetic clusters in a phylogenetic analysis, with CS-4, EbpC, G, NESH1 to NESH3, and NECA1 to NECA5 distributed in zoonotic group 1 and BEB4, BEB6, CM7, EbpI, J, OEB1, and NESH4 to NESH6 distributed in potentially host-adapted group 2. Nearly 70% of cases of E. bieneusi infections in sheep were contributed by human-pathogenic genotypes BEB6, CS-4, and EbpC, and over 80% of those in cattle were by genotypes BEB4, CS-4, EbpC, I, and J. The cooccurrence of genotypes BEB4, CS-4, EbpC, I, and J in domestic ruminants and children in northeast China and the identification of BEB6 and EbpC in humans and water in central China imply the possibility of zoonotic transmission. This study also summarizes E. bieneusi genotypes obtained from ruminants worldwide and displays their host ranges, geographical distributions, and phylogenetic relationships. The data suggest a host range expansion in some group 2 genotypes (notably BEB4, BEB6, I, and J) that were previously considered to be adapted to ruminants. We should be concerned about the increasing zoonotic importance of group 2 genotypes with low host specificity.