Molecular Detection of Enterocytozoon bieneusi in Free-Range Sheep and Domestic Dogs from the Greater Hinggan Mountains Area of China

Simple Summary Enterocytozoon bieneusi (E. bieneusi) is a microsporidian parasite infecting humans and animals globally, yet data on its occurrence in free-range livestock and companion animals in rural areas remain limited. In this study, fecal samples from 95 free-range sheep and 140 dogs in two villages of the Greater Hinggan Mountains, China, were examined using nested PCR targeting the ITS region of the rDNA gene. The overall infection rate of E. bieneusi was 3.0% (7/235), including 5.3% (5/95) in sheep and 1.4% (2/140) in dogs. Sequence analysis identified two known genotypes in sheep (BEB6 and NESH4, phylogenetic group 2) and one in dogs (CHN-F1, phylogenetic group 1), with CHN-F1 reported in dogs for the first time. Notably, genotype BEB6 is a recognized zoonotic type, highlighting sheep as a potential source of human infection and environmental contamination. These findings expand current knowledge on the genetic diversity of E. bieneusi in rural settings and underscore the risk of cross-species transmission between humans and animals.