The prevalence and subtype distribution of Blastocystis sp. in humans and domestic animals in family units in Heilongjiang Province, China

Background: Blastocystis is an enteric protozoan infecting humans and animals all over the world. Domestic animals play an important role in transmitting parasites to other domestic animals and humans. In the present study, a survey was conducted on Blastocystis among humans and domestic animals sharing habitats in northeastern China’ s Heilongjiang Province, in order to investigate the prevalence, the subtype distribution, as well as to evaluate the risk of the zoonotic transmission of Blastocystis isolates. Methods: : A total of 314 (57 humans, 257 domestic animals) fecal samples were collected from 33 family households in three villages. The corresponding sequences of the barcode region of the SSU rRNA gene obtained in this study were subject to molecular analysis for subtype and allele identification of Blastocystis sp. Results: : The prevalence of Blastocystis was 14.0% (8/57) in humans and 17.9% (46/257) in domestic animals. Eight PCR-positive human samples, 100% (8/8) were successfully subtyped, allowing the identification of the ST3, followed by ST1 and ST2. The 46 PCR-positive animal samples, 65.2% (30/46) were successfully subtyped, ST5 followed by ST1 in pigs, ST5 in goats; ST10, ST14 followed by ST3 in cattle; ST7 in chickens. Phylogenetic analysis showed that Blastocystis ST3 sequences from humans in two geographical locations formed two distinct clades. Alleles were identified using the Blastocystis 18S database and a total of 10 different alleles were found in six STs. Conclusions: : The present study is the first description of the prevalence and subtype (allele) distribution of Blastocystis sp. by molecular analysis in humans and domestic animals in family units in China. Blastocystis ST2 in humans and ST5 in goats were reported in Heilongjiang Province for the first time. ST1 (a4) and ST3 (a34) overlaps were observed in humans and some domestic animal species (pig and cattle). The findings of potentially zoonotic subtypes in domestic animals suggest that these animals may serve as reservoirs of human Blastocystis sp. infections, thus help develop more efficient, targeted control strategies against human blastocystosis.