Blastocystis sp. in human populations: Pooled prevalence and subtype distribution from a systematic review and...

Blastocystis is widely detected in human populations, yet prevalence estimates vary substantially across geographic regions, population settings, and diagnostic approaches. We systematically reviewed cross-sectional surveys published from 2015 to 2025 that investigated non-disease-selected human populations. Across 137 eligible survey units from 47 countries, 562,327 participants and 26,697 positive detections were included. The crude participant-level positivity was 4.7%, whereas the random-effects pooled prevalence across published surveys was 17.9% (95% CI: 13.9%-22.6%; 95% PI: 0.7%-87.5%; I² = 99.7%). Regional pooled estimates were 44.2% in Africa, 36.7% in the Americas, 8.4% in Asia, and 7.2% in Europe; however, these comparisons should be interpreted descriptively because substantial residual heterogeneity and study-level confounding remained. Population-group differences were not statistically significant (P = 0.074), while the three broad diagnostic-strategy groups were summarized descriptively because multimodal protocols were heterogeneous. Sensitivity analyses restricted to population-based surveys and community/household surveys yielded pooled estimates of 15.8% and 13.0%, respectively. Among 62 studies reporting molecular subtype information, 5220 isolates were assigned single subtypes, while 658 mixed-subtype detections from 18 studies were summarized separately. ST3, ST1, and ST2 were among the predominant reported subtypes. These findings summarize available published surveillance data rather than a population-weighted global burden estimate and highlight the need for standardized sampling frameworks, harmonized molecular workflows, and integrated One Health investigations to clarify Blastocystis epidemiology and transmission ecology.