Abstract: Objective To determine the prevalence and subtypes of Blastocystis in pet dogs in Anhui and Zhejiang Provinces. Methods Pet dog fecal samples were collected from veterinary clinics in Baohe District of Hefei City, Xuanzhou District of Xuancheng City, Fengyang County and Mingguang City of Chuzhou City, Longzihu District of Bengbu City, Si County of Suzhou City in Anhui Province, as well as in Yuhang District of Hangzhou City in Zhejiang Province from April to December, 2013. Blastocystis was detected by microscopic examination as well as nested PCR and single-step PCR based on small subunit ribosomal DNA sequences. The PCR products were sequenced, and Blastocystis subtypes were assigned. Results A total of 315 pet dog fecal samples were collected. The incidence of Blastocystis infection determined by microscopic examination, nested PCR and single-step PCR was 1.3%（4/315）, 1.9%（6/315） and 1.9%（6/315）, respectively. In addition, the two PCR methods both revealed Blastocystis infection only in Chuzhou City（3.4%, 1/29） and Hefei City（5.6%, 4/72）. The pet dogs in Chuzhou City carried ST1 and ST2 subtypes while those in Hefei carried only ST1. There was no significant difference in infection rate between adult and young dogs and between male and female dogs. Conclusion Blastocystis infection exists in pet dogs in Chuzhou City and Hefei City.

Key words: Blastocystis, Subtype, Pet dog, Anhui, Zhejiang