Prevalence of Free-Living Amoebae in Various Water Sources in Iran: A Systematic Review and Meta-Analysis

Free-living amoebae (FLA) are widespread protozoa found in various water sources and can cause serious human infections. Identifying their occurrence and diversity in environmental waters is crucial for public health risk assessment and prevention. This study aimed to systematically review the prevalence and species/genotype distribution of FLA in different Iranian water sources.

A systematic search was conducted in major international (PubMed, Scopus, Web of Science, Google Scholar) and Persian (SID, MagIran) databases from inception up to June 6, 2025. Eligible studies reporting the detection of FLA from Iranian water sources were included. In total, 58 studies met the inclusion criteria, encompassing 4,387 water samples from 24 provinces. Water sources were categorized into five groups: drinking/domestic water (six studies, 454 samples), natural recreational water (14 studies, 606 samples), artificial recreational water (16 studies, 1,666 samples), surface/stagnant water (eight studies, 703 samples), and mixed water (14 studies, 958 samples). Statistical analyses were performed using Comprehensive Meta-Analysis (CMA) software, applying a random-effects model with 95% confidence intervals (CIs). Heterogeneity was assessed using the I² statistic. Sensitivity analysis was performed by sequentially removing individual studies, and meta-regression was applied to explore potential sources of heterogeneity. Subgroup analyses were conducted based on publication year, water type, geographical region, climate zone, and sample size.

The pooled prevalence of FLA in Iranian water sources was 40.2% (95% CI: 33.7-47.1%). Among water categories, the highest contamination was observed in surface/stagnant waters (59.9%), followed by mixed waters (42.5%), natural recreational waters (42.1%), drinking/domestic waters (38.0%), and artificial recreational waters (29.0%). By climate zone, water sources in warm/humid and temperate/humid areas showed the highest prevalence (49.2% and 44.7%, respectively). Provincially, the highest contamination rates were recorded in Sistan and Baluchestan (88.2%), Hamedan (87.5%), Kermanshah (76.7%), Khuzestan (71.7%), and North Khorasan (68.0%). Ten FLA genera were reported from Iranian water resources: Acanthamoeba, Naegleria, Vahlkampfia, Vermamoeba, Vannella, Platyamoeba, Saccamoeba, Balamuthia, Protacanthamoeba, and Stenamoeba. Reported species/genotypes included Acanthamoeba T2-T6, T11, T13, and T15; Naegleria fultoni, N. pagei, N. clarki, N. carteri, N. australiensis, N. gruberi, N. dobsoni, N. americana, N. polaris, N. lovaniensis, and N. philippinensis; Vahlkampfia avara; Vermamoeba vermiformis; Vannella persistens; Saccamoeba limax; Stenamoeba polymorpha; Balamuthia mandrillaris; and Protacanthamoeba bohemica. Sensitivity analysis confirmed the robustness of the pooled estimates, while meta-regression identified sample size as a significant contributor to result variability and a potential source of heterogeneity.

FLA are widely prevalent in various water sources of Iran, especially in surface waters and warm/humid climates. The presence of multiple pathogenic genera and genotypes highlights significant health risks. Continuous monitoring and targeted control strategies are essential to reduce exposure and guide future research on environmental and epidemiological factors influencing FLA distribution.