Widespread distribution of human-infective Enterocytozoon bieneusi genotypes in small rodents in northeast China and phylogeny and zoonotic implications revisited

Enterocytozoon bieneusi features high genetic diversity among host species and environmental sources and over 500 genotypes in 11 phylogenetic groups have been defined. Here we investigated 291 small rodents in Heilongjiang province, northeast China, for the presence of E. bieneusi by PCR of the ribosomal internal transcribed spacer (ITS). Nine of 60 (15.0 %) gray squirrels from a park in Harbin, 120 of 201 (59.7 %) guinea pigs from a pet shop in Harbin, and two of 30 (6.7 %) peridomestic rats from a pasture in Qiqihar were positive for the parasite. Six known genotypes (EbpB, SCC-1, SCC-2, D, S7 and HLJ-CP1) and two novel genotypes (NESQ1 and NEGP1) were identified by sequence analysis of the ITS, with EbpB, SCC-1, SCC-2 and NESQ1 found in squirrels, D, S7 and NEGP1 in guinea pigs, and EbpB and HLJ-CP1 in rats. Widespread distribution of human-infective Group 10 genotype S7 and Group 1 genotype D in guinea pigs raised our concerns about the importance of pet animals as zoonotic reservoirs of microsporidiosis. Co-occurrence of Group 1 genotypes D and HLJ-CP1 in cancer patients and rodents in Heilongjiang indicated a possibility of zoonotic transmission. The host range of Group 1 genotype EbpB previously considered pig-adapted was extended. A potential variant of genotype S7, namely NESQ1, went into the existing Group 10 in phylogenetic analysis. The other new genotype, NEGP1, was clustered in an undefined clade we proposed as Group 15. With the emerging epidemiologic evidence, the host specificity of existing E. bieneusi genotypes is now being challenged.