Epidemiology of Blastocystis infection from 1990 to 2019 in China.

BACKGROUND: Blastocystis is ubiquitous presence in animals and humans worldwide and has a high level genetic diversity. The aim of this study was to conduct a summary of Blastocystis prevalence, subtypes (STs) in humans and animals in China and depict their distribution. METHODS: We searched for the articles related to epidemiology of Blastocystis in humans and animals throughout China which published from January 1, 1990, to July 31, 2019 in the following databases: PubMed, China National Knowledge Infrastructure (CNKI) and Wanfang database. The keywords were Blastocystis and one of the following ones: STs, subtypes, distribution, epidemiology, prevalence, infection, molecular, geographic, intestinal parasites, genetic diversity and characterization. RESULTS: In recent years, various molecular epidemiological studies have been carried out in some provinces/regions of China to identify subtypes of Blastocystis. Infants and young children, school students, hospitalized diarrhea patients, HIV/AIDS patients, tuberculosis patients, and cancer patients as respondents had been included. ST1-ST7 and ST12 were the main subtypes in Chinese population. Moreover, surveys of Blastocystis infection in animal were also conducted in some provinces of China. A variety of animals were investigated including pigs, cattle, sheep, yak, giant panda, and crested ibis (Nipponia nippon) with the main subtypes of ST1-ST8, ST10, ST12-ST14. CONCLUSIONS: In recent years, some provinces/regions in China have conducted various molecular epidemiological studies to identify the Blastocystis subtypes. It is important to focus on new subtypes and mixed subtypes of infection, while increasing data on ribosomal alleles. We encourage the scientific community to start research on humans and surrounding animals (including domestic and wild animals) to better understand the possibility of Blastocystis transmission between humans and animals. We call for action among researchers studying intestinal parasitic diseases (Blastocystis), start drawing the subtype of Blastocystis and increase the subtype related to its clinical symptoms.

Molecular Epidemiology and Risk Factors of Blastocystis sp. Infections Among General Populations in Yunnan Province, Southwestern China.

BACKGROUND: Blastocystis is a common enteric parasite of controversial pathogenic roles in human diseases. Although the prevalence of Blastocystis infections has been investigated in a diverse range of populations, there is little knowledge on the molecular epidemiology and risk factors of Blastocystis infections among general populations in southeastern China. MATERIALS AND METHODS: A total of 507 individuals were randomly selected in Yunnan province, China from July 2016 to March 2017. Stool specimens were sampled for detection of Blastocystis sp. using PCR assay, and the risk factors of Blastocystis infections were identified. Blastocystis isolates were subtyped, and the associations of Blastocystis infections and subtypes with clinical manifestations were examined. RESULTS: The overall detection rate of Blastocystis sp. was 9.47% (95% CI: 7.13-12.44%). Toilet type (OR = 3.248, 95% CI: 1.245-8.473), anemia (OR = 2.601, 95% CI: 1.245-8.473) and type of daily drinking water (OR = 3.11, 95% CI: 1.557-6.213) were identified as risk factors of Blastocystis infections; however, Blastocystis infections showed no associations with clinical symptoms. Four subtypes (ST1 to ST4) were characterized in Blastocystis isolates, in which ST3 was predominant (4.73%, 95% CI: 3.2-6.94%), followed by ST1 (3.16%, 95% CI: 1.95-5.07%), ST4 (1.38%, 95% CI: 0.07-2.82%) and ST2 (0.2%, 95% CI: 0-1.11%). In addition, ST1 subtype infection was found to correlate with anemia (OR = 4.66, 95% CI: 1.631-14.314). CONCLUSIONS: There is a high prevalence of Blastocystis infections among general populations in Yunnan province, southwestern China, and toilet type, anemia and type of daily drinking water are risk factors of Blastocystis infections. ST3 is the dominant subtype of Blastocystis sp. characterized, and ST1 correlates with anemia. Improving hygiene conditions, developing healthy lifestyles and intensifying health education programs are strongly recommended to reduce the prevalence and transmission potential of Blastocystis infections.