Abstract: [Objective] This study aimed to understand the infection status and subgenotype distribution of Blastocystis in Hu sheep in large-scale farms in Hangzhou City, China. [Method] A total of 167 fresh fecal samples of Hu sheep were collected from four large-scale farms in Hangzhou City, and their whole genomic DNA were extracted. PCR assay targeting the small-subunit ribosomal RNA （SSU rRNA） gene was performed using the fecal DNA samples as templates, and the obtained positive amplification products were sequenced. The subgenotypes of Blastocystis were identified through sequence alignment. Phylogenetic tree was constructed to analyze their genetic evolutionary relationships. [Result] Among the 167 samples, 18 were positive for Blastocystis, with an infection rate of 10.78% （18/167）. Three farms had the prevalence of Blastocystis, with infection rates of 21.43% （3/14）, 21.21% （14/66） and 2.13% （1/47）, respectively. One farm had no Blastocystis detection. There were extremely significant （P<0.01） differences in the infection rates of Blastocystis among different farms. Seven subgenotypes of Blastocystis were identified, including ST7 （n=1）, ST10 （n=9）, ST21 （n=3）, ST23 （n=1）, ST24 （n=2）, ST26 （n=1） and ST30 （n=1）. ST10 was found as the dominant subgenotype （9/18, 50.00%）. Based on the phylogenetic tree analysis of the SSU rRNA gene of Blastocystis, it was found that six gene subgenotypes were clustered into one large group, with ST10 and ST23 clustering into one subgroup, ST21, ST26 and ST30 clustering into one subgroup, and ST24 clustering into one subgroup as well, while ST7 was clustered into another group. [Conclusion] Blastocystis infection in Hu sheep was common in Hangzhou City, and the subgenotypes of Blastocystis had genetic diversity. The results obtained in this study provided basic data for the investigation of sheep Blastocystis infection status in China.

Key words: Blastocystis, detection, identify, subgenotype, Hu sheep