Restricted accessReview articleFirst published online 2025-07
A Worldwide Systematic Review and Meta-Analysis of the Prevalence and Subtype Distribution of Blastocystis sp. in Water Sources: A Public Health Concern
Contaminated water sources can result in outbreaks of parasitic infections such as Blastocystis sp. in communities, creating a substantial strain on healthcare systems and affecting the general health of the population. To ascertain the prevalence and subtype distribution of Blastocystis sp. in water sources globally, a systematic review and meta-analysis of published papers up to May 19, 2024 were carried out. A thorough search of multiple electronic databases (PubMed, Scopus, Google Scholar, and Web of Science) identified 24 studies/28 datasets meeting the inclusion criteria, encompassing 2,451 water samples from 15 countries worldwide. Water samples comprised wastewater (six datasets, 285 samples), tap/drinking water (10 datasets, 253 samples), surface water (eight datasets, 1013 samples), and uncategorized water (four datasets, 900 samples). Total estimates and 95% confidence intervals (CIs) were computed using a random-effects model. This review found that 18.8% (95% CI: 12.8–26.9%) of examined water samples contained Blastocystis sp. Wastewater showed the highest Blastocystis sp. infection rate at 35.5% (95% CI: 13.5–66.1%), followed by tap/drinking water at 19.1% (95% CI: 9.5–34.5%), surface water at 17.6% (95% CI: 7.2–36.8%), and uncategorized water at 9.9% (95% CI: 4.1–21.8%). Sensitivity analysis assessed weighted prevalence variations following the exclusion of individual studies. Subgroup analysis of Blastocystis sp. prevalence was performed based on publication years, countries, continents, WHO regions, sample sizes, and diagnostic methods. Water samples can be the source of infection for nine Blastocystis sp. subtypes (STs) (ST1-ST4, ST6, ST8, ST10, ST21, and ST24), with seven STs (ST1-ST4, ST6, ST8, and ST10) capable of infecting humans. It is important to take preventative and control measures, improve the cleanliness and quality of water sources, and promote public health awareness due to the presence of different parasites such as Blastocystis sp. in water sources.
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References
1.
AbdullahSH, DyaryHO. Epizootiology of Blastocystis spp.: A Parasite with Zoonotic Concern. Volume;2. Zoonosis, Unique Sci Publ: Faisalabad, Pakistan; 2023; pp. 261–274; doi: 10.4727/8/book.zoon/2023.69
2.
AdamskaM. First report of Blastocystis sp. subtypes in natural water bodies in North-Western Poland: A one-year monitoring. Int J Environ Health Res, 2022; 32(4):862–869; doi: 10.1080/09603123.2020.1803804
3.
AsghariA, BanavandS, AkhlaghzadehM, et al.First molecular identification and subtyping of Blastocystis sp. in the most consumed edible marine fish of Iran: A foodborne concern. Acta Parasitol, 2024a;69(1):446–452; doi: 10.1007/s11686-023-00769-9
4.
AsghariA, SadeghipourZ, HassanipourS, et al.Association between Blastocystis sp. Infection and immunocompromised patients: A systematic review and meta-analysis. Environ Sci Pollut Res Int, 2021; 28(43):60308–60328; doi: 10.1007/s11356-021-16187-1
5.
AsghariA, YousefiA, BadaliR, et al.First molecular subtyping and zoonotic significance of Blastocystis sp. in dromedary (C. Dromedarius) and bactrian (C. Bactrianus) camels in Iran: A molecular epidemiology and review of available literature. Vet Med Sci, 2024b;10(3):e1442; doi: 10.1002/vms3.1442
6.
AsghariA, YousefiA, MohammadiMR, et al.Comparative molecular epidemiology, subtype distribution, and zoonotic potential of Blastocystis sp. in equus animals (Horses, Donkeys, and Mules) in Northwestern Iran. Comp Immunol Microbiol Infect Dis, 2024c;106:102124; doi: 10.1016/j.cimid.2024.102124
7.
AttahAO, SanggariA, LiLI, et al.Blastocystis occurrence in water sources worldwide from 2005 to 2022: A review. Parasitol Res, 2023; 122(1):1–10; doi: 10.1007/s00436-022-07731-0
8.
BaldurssonS, KaranisP. Waterborne transmission of protozoan parasites: Review of worldwide outbreaks–an update 2004–2010. Water Res, 2011; 45(20):6603–6614; doi: 10.1016/j.watres.2011.10.013
9.
BanaticlaJEG, RiveraWL. Detection and subtype identification of Blastocystis isolates from wastewater samples in the Philippines. J Water Health, 2011; 9(1):128–137; doi: 10.2166/wh.2010.127
10.
BaratiM, KarimiPourA, RahmanianV, et al.Global prevalence and subtype distribution of Blastocystis sp. in rodents, birds, and water supplies: A systematic review and meta-analysis. Prev Vet Med, 2022; 208:105770; doi: 10.1016/j.prevetmed.2022.105770
11.
BastaminejadS, EskandariP, MohammadiMR, et al.Identification of Blastocystis spp. in urban rodents of different districts in Southwestern Iran: Subtype distribution and possible zoonotic potential. Acta Parasitol, 2024; 69(1):922–928; doi: 10.1007/s11686-024-00815-0
12.
BasualdoJA, CórdobaMA, de LucaMM, et al.Intestinal parasitoses and environmental factors in a rural population of Argentina, 2002–2003. Rev Inst Med Trop Sao Paulo, 2007; 49(4):251–255; doi: 10.1590/S0036-46652007000400011
13.
BasualdoJ, PezzaniB, De LucaM, et al.Screening of the municipal water system of La Plata, Argentina, for human intestinal parasites. Int J Hyg Environ Health, 2000; 203(2):177–182; doi: 10.1078/S1438-4639(04)70025-5
14.
EfstratiouA, OngerthJE, KaranisP. Waterborne transmission of protozoan parasites: Review of worldwide outbreaks-an update 2011–2016. Water Res, 2017; 114:14–22; doi: 10.1016/j.watres.2017.01.036
15.
ElseadawyR, AbbasI, Al-ArabyM, et al.Occurrence and molecular characterization of Acanthamoeba, Naegleria Fowleri and Blastocystis in water samples from various sources in Egypt. Acta Trop, 2023; 237:106733; doi: 10.1016/j.actatropica.2022.106733
16.
ErogluF, KoltasIS. Evaluation of the transmission mode of B. hominis by using PCR method. Parasitol Res, 2010; 107(4):841–845; doi: 10.1007/s00436-010-1937-4
17.
Flores-CarreroAD, Peña-ContrerasZ, Dávila-VeraD, et al.Investigación de Blastocystis sp. En agua de consumo humano en una población escolar de la zona rural del Estado Mérida-Venezuela. Kasmera, 2011; 39(2):123–129.
18.
GantoisN, LamotA, SeesaoY, et al.First report on the prevalence and subtype distribution of Blastocystis sp. In edible marine fish and marine mammals: A large scale-study conducted in Atlantic Northeast and on the coasts of Northern France. Microorganisms, 2020; 8(3):460; doi: 10.3390/microorganisms8030460
19.
González-BarrioD. Zoonoses and wildlife: One health approach. Animals, 2022; 12(4):480.
20.
IthoiI, JaliA, MakJW, et al.Occurrence of Blastocystis in water of two rivers from recreational areas in Malaysia. J Parasitol Res, 2011; 2011(1):123916; doi: 10.3390/ani12040480
21.
JavanmardE, RahimiHM, NiyyatiM, et al.Molecular analysis of Blastocystis sp. and its subtypes from treated wastewater routinely used for irrigation of vegetable farmlands in Iran. J Water Health, 2019; 17(5):837–844; doi: 10.2166/wh.2019.045
22.
JinathamV, MaxamhudS, PopluechaiS, et al.Blastocystis one health approach in a rural community of Northern Thailand: Prevalence, subtypes and novel transmission routes. Front Microbiol, 2021; 12:746340; doi: 10.3389/fmicb.2021.746340
23.
JinathamV, NonebudsriC, WandeeT, et al.Blastocystis in tap water of a community in Northern Thailand. Parasitol Int, 2022; 91:102624; doi: 10.1016/j.parint.2022.102624
24.
JinathamV, WandeeT, NonebudsriC, et al.Blastocystis subtypes in raw vegetables from street markets in Northern Thailand. Parasitol Res, 2023; 122(4):1027–1031; doi: 10.1007/s00436-023-07781-y
25.
KaramanÜ, KolörenZ. Ordu ilinden alinan su örneklerinde Blastocystis alt türlerinin araştirilmasi. Türkiye Parazitolojii Derg, 2019; 43(3):111; doi: 10.4274/tpd.galenos.2019.5976
26.
KaramanÜ, KolörenZ, SeferoğluO, et al.Samsun Il ve ilçelerinden alinan çevresel sularda parazitlerin varliği. Turkiye Parazitol Derg, 2017; 41(1):19–21.
27.
KhalifaR, AhmadAK, Abdel-HafeezEH, et al.Present status of protozoan pathogens causing water-borne disease in northern part of El-Minia governorate, Egypt. J Egypt Soc Parasitol, 2014; 44(3):559–566; doi: 10.2160/8/jesp.2014.90143
28.
KolorenZ, GulabiBB, KaranisP. Molecular identification of Blastocystis sp. subtypes in water samples collected from black sea, Turkey. Acta Trop, 2018; 180:58–68; doi: 10.1016/j.actatropica.2017.12.029
29.
KumarasamyV, RajamanikamA, AnbazhaganD, et al.Systematic review and meta-analysis: Epidemiology of human Blastocystis spp. infection in Malaysia. Trop Med Infect Dis, 2023; 8(8):415; doi: 10.3390/tropicalmed8080415
30.
KurizkyPS, dos Santos NetoLL, AiresRB, et al.Opportunistic tropical infections in immunosuppressed patients. Best Pract Res Clin Rheumatol, 2020; 34(4):101509; doi: 10.1016/j.berh.2020.101509
31.
LeeLI, ChyeTT, KarmacharyaBM, et al.Blastocystis sp.: Waterborne zoonotic organism, a possibility? Parasit Vectors, 2012; 5:130; doi: 10.1186/1756-3305-5-130
32.
LeelayoovaS, SiripattanapipongS, ThathaisongU, et al.Drinking water: A possible source of Blastocystis spp. subtype 1 infection in schoolchildren of a rural community in central Thailand. Am J Trop Med Hyg, 2008; 79(3):401–406.
33.
MatovelleC, QuílezJ, TejedorMT, et al.Subtype distribution of Blastocystis spp. in patients with gastrointestinal symptoms in Northern Spain. Microorganisms, 2024; 12(6):1084; doi: 10.3390/microorganisms12061084
34.
MoherD, ShamseerL, ClarkeM, et al.PRISMA-P Group. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Syst Rev, 2015; 4(1):1–9; doi: 10.1186/2046-4053-4-1
35.
MorenoY, Moreno-MesoneroL, AmorósI, et al.Multiple identification of most important waterborne protozoa in surface water used for irrigation purposes by 18S RRNA amplicon-based metagenomics. Int J Hyg Environ Health, 2018; 221(1):102–111; doi: 10.1016/j.ijheh.2017.10.008
36.
MunnZ, MoolaS, RiitanoD, et al.The development of a critical appraisal tool for use in systematic reviews addressing questions of prevalence. Int J Health Policy Manag, 2014; 3(3):123–128; doi: 10.1517/1/ijhpm.2014.71
37.
NithyamathiK, ChandramathiS, KumarS. Predominance of Blastocystis sp. infection among school children in Peninsular Malaysia. PLoS One, 2016; 11(2):e0136709; doi: 10.1371/journal.pone.0136709
38.
NoradilahSA, LeeIL, AnuarTS, et al.Blastocystis spp. contaminated water sources in aboriginal settlements. Trop Biomed, 2017; 34(1):110–117.
39.
OmarovaA, TussupovaK, BerndtssonR, et al.Protozoan parasites in drinking water: A system approach for improved water, sanitation and hygiene in developing countries. Int J Environ Res Public Health, 2018; 15(3):495; doi: 10.3390/ijerph15030495
40.
PalM, AyeleY, HadushM, et al.Public health hazards due to unsafe drinking water. Air Water Borne Dis, 2018; 7(1000138); doi: 10.4172/2167-7719.1000138
41.
RichardRL, IthoiI, Abd MajidMA, et al.Monitoring of waterborne parasites in two drinking water treatment plants: A study in Sarawak, Malaysia. Int J Environ Res Public Health, 2016; 13(7):641; doi: 10.3390/ijerph13070641
42.
RyckmanM, GantoisN, DominguezRG, et al.Molecular identification and subtype analysis of Blastocystis sp. isolates from wild mussels (Mytilus Edulis) in Northern France. Microorganisms, 2024; 12(4):710; doi: 10.3390/microorganisms12040710
43.
SantinM, FigueiredoA, MolokinA, et al.Division of Blastocystis ST10 into three new subtypes: ST42‐ST44. J Eukaryot Microbiol, 2024; 71(1):e12998; doi: 10.1111/jeu.12998
44.
SappenfieldE, JamiesonDJ, KourtisAP. Pregnancy and susceptibility to infectious diseases. Infect Dis Obstet Gynecol, 2013; 2013(1):752852; doi: 10.1155/2013/752852
45.
ShamsM, BahramiAM, MousivandA, et al.First molecular characterization of Blastocystis subtypes from domestic animals (Sheep and Cattle) and their animal‐keepers in Ilam, Western Iran: A zoonotic concern. J Eukaryot Microbiol, 2024; 71(3):e13019; doi: 10.1111/jeu.13019
46.
SpeichB, CrollD, FürstT, et al.Effect of sanitation and water treatment on intestinal protozoa infection: A systematic review and meta-analysis. Lancet Infect Dis, 2016; 16(1):87–99; doi: 10.1016/S1473-3099(15)00349-7
47.
StensvoldCR, LebbadM, HansenA, et al.Differentiation of Blastocystis and parasitic archamoebids encountered in untreated wastewater samples by amplicon-based next-generation sequencing. Parasite Epidemiol Control, 2020; 9:e00131; doi: 10.1016/j.parepi.2019.e00131
48.
SureshK, SmithHV, TanTC. Viable Blastocystis cysts in Scottish and Malaysian sewage samples. Appl Environ Microbiol, 2005; 71(9):5619–5620; doi: 10.1128/AEM.71.9.5619-5620.2005
49.
WangY, ZhangC, NanH, et al.Molecular Detection and Subtype Distribution of Blastocystis sp. in Cold-Water Fish and Cultured Water. IJA; 2024.
50.
WatersE, AhmedW, HamiltonKA, et al.Protozoan pathogens Blastocystis and Giardia spp. in roof-harvested rainwater: The need to investigate the role of the common brushtail possum (Trichosurus Vulpecula) and other potential sources of zoonotic transmission. J Water, Sanit Hyg Dev, 2019; 9(4):780–785; doi: 10.2166/washdev.2019.064
51.
ZahediA, GreayTL, PapariniA, et al.Identification of eukaryotic microorganisms with 18S RRNA next-generation sequencing in wastewater treatment plants, with a more targeted NGS approach required for Cryptosporidium detection. Water Res, 2019; 158:301–312; doi: 10.1016/j.watres.2019.04.041
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