Cross-sectional surveys and subtype classification of human Blastocystis isolates from four epidemiological settings in China.

The prevalence and geographical distribution of the intestinal protozoa Blastocystis in humans across China is unknown, and the relative importance of different subtypes has yet to be investigated. We assessed the community prevalence and relative frequencies of different Blastocystis subtypes in four epidemiological settings in China, i.e., Shanghai municipality, Yongjia county (Zhejiang province), Eryuan county, and Menghai county (both Yunnan province). Blastocystis infection was detected with the culture method, and the subtype was identified with polymerase chain reaction using a set of subtype-specific primers. The prevalence at the four study settings was 1.9, 5.9, 18.4, and 32.6%, respectively. People aged greater than or equal to 60 years had a higher prevalence in the former two settings, Shanghai and Yongjia, whereas the highest infection rate was found among individuals aged 10-17 years in the latter two settings, Eryuan and Menghai. A higher prevalence was found in men in the former two settings but in women in the latter two settings. Five different Blastocystis subtypes were identified from the 192 isolates. Subtype 3 was the predominant type, followed by subtype 1. In conclusion, the epidemiology of Blastocystis varies across China.