Blastocystis in tap water of a community in northern Thailand

Molecular prevalence and subtype characteristics of Blastocystis among school children in Hainan, the tropical island province of China

Blastocystis is one of the most common zoonotic intestinal protozoa with global distribution and can cause gastrointestinal syndrome mainly characterized by diarrhea. School children are the main susceptible population. No epidemiological data on Blastocystis among school children in Hainan, the only tropical island province in China. Between March 2021 and June 2023, 1973 fecal samples were collected from school children across three regions in Hainan province. Blastocystis was examined by amplifying the small subunit ribosomal RNA (SSU rRNA) gene via polymerase chain reaction (PCR), and subtypes were identified through DNA sequencing and phylogenetic analysis. The overall prevalence of Blastocystis was 7.3 % (144/1973). The differences in infection rates across different regions, nationalities, and educational stages are statistically significant (P < 0.001). Five subtypes were identified, of which ST3 was the dominant subtype (60.4 %; 87/144), followed by ST1 (27.8 %; 40/144), ST7 (10.4 %; 15/144), ST6 (0.7 %; 1/144), and ST2 (0.7 %; 1/144). 42 known sequences and 15 novel sequences were identified including eight new variations of the ST1 (ST1-16∼ST1-23) with similarities ranging from 98.3 % to 99.78 % and seven new variations of the ST7 (ST7-7∼ST7-13) with similarities ranging from 97.7 % to 99.79 % by intra-subtype genetic polymorphisms analysis. The results evaluate the public health risks of Blastocystis among school children in Hainan and the sources of infection were discussed, providing important basic data for the effective prevention and control of intestinal parasitic diseases in Hainan.

Existence of Blastocystis infection in bar-headed goose (Anser indicus)

Blastocystis is a common intestinal protist in humans and animals. Currently, Blastocystis infection in bar-headed geese is unknown. To understand the prevalence and distribution of Blastocystis subtypes in bar-headed geese, fecal samples were collected from 358 bar-headed geese in three regions. The total infection rate of Blastocystis in bar-headed in China was 5.9% (21/358), with 5.0% (6/120) in Aba (Ngawa) Tibetan and Qiang Autonomous Prefect, Sichuan province, 11.8% (14/119) in Maqu county, Gansu province, and 0.8% (1/119) in Caohai, Wei ning county, Guizhou province. The differences in prevalence rates by region were statistically significant. Sequences analyses showed that one known subtype (ST7, n = 16) and one potentially novel ST (n = 5) in bar-headed geese were detected in this study. This is the first report on the prevalence and subtype distribution of Blastocystis in bar-headed geese, which will improve our understanding of the epidemiology and public health implications of Blastocystis infection in wild migratory birds.

Genetic diversity and host specificity of Blastocystis in reptiles, Eastern Thailand

Blastocystis inhabits the digestive tracts of a diverse range of hosts. Transmission patterns, including host specificity, and the clinical and public health significance of Blastocystis in humans remain poorly understood. This study aimed to investigate the distribution and genetic diversity of Blastocystis in herbivorous and carnivorous reptiles in Eastern Thailand. A total of 501 faecal samples were collected from 363 iguanas, 79 bearded dragons, 50 tortoises, and nine snakes in an animal breeding farm in Chonburi Province, Eastern Thailand. Detection and differentiation of Blastocystis was based on amplification, sequencing, and phylogenetic analysis of specific small subunit (SSU) ribosomal RNA genes from faecal DNA extracted from the samples. Altogether 101/501 samples (20 %) were polymerase chain reaction (PCR) and sequencing-positive for Blastocystis, 90 (89 %) of which were from iguanas; the remaining positive samples were from African spurred tortoise (n=6), Bearded dragon (n=3), Leopard tortoise (n=1), and Red-footed tortoise (n=1). Phylogenetic analysis revealed that most of the Blastocystis sequences from iguanas were largely similar, and they were distinct from those of the tortoises. Subtype 17 was found in the three bearded dragons and likely reflected Blastocystis from prey animals. This is the largest survey of Blastocystis in reptiles to date. Remarkable differences in Blastocystis colonization rates and genetic diversity were observed between iguanas and other reptile orders, and what was considered Blastocystis colonization was only observed in herbivorous reptiles.

Molecular detection and genotyping of Dientamoeba fragilis and Blastocystis sp. in housefly Musca domestica (Diptera: Muscidae): first report for Dientamoeba fragilis

Dientamoeba fragilis and Blastocystis sp. are single-celled protozoan parasites of humans and animals. Although they are found in the intestines of healthy hosts, the pathogenicity of them is still unclear. To date, there is no report on D. fragilis and only two studies (without subtyping) on the occurrence of Blastocystis sp. in Musca domestica. In this study, fly samples were collected from livestock farms and their surroundings in the Kirsehir province (Central Anatolia Region) of Türkiye from May to August 2023. A total of 150 microscopically identified M. domestica samples were analyzed for the detection of D. fragilis and Blastocystis sp. molecularly. The overall prevalence of Blastocystis sp. and D. fragilis in M. domestica was determined to be 3.3% (5/150) and 8.0% (12/150), respectively. The SSU rRNA gene sequences of the isolates indicated genotype 1 of D. fragilis. Eleven isolates were identical and represented a single isolate (KAU-Dfrag1). BLAST analysis of KAU-Dfrag1 indicated identity with the isolates reported from humans, cattle, sheep, and budgerigars. The other isolate (KAU-Dfrag2) was polymorphic at two nucleotides from KAU-Dfrag1 and three nucleotides from known genotypes from GenBank and represented a variant of genotype 1. The Blastocystis sp. isolates were found to be identical and represent a single genotype (KAU-Blast1). BLAST analysis revealed that the KAU-Blast1 genotype belonged to the potentially zoonotic subtype 5 (ST5) and exhibited the highest genetic identity (ranging from 99.4 to 99.6%) with pigs, cattle, and sheep from different countries. Our study provides the first data on the molecular prevalence, epidemiology, and genotypic characterization of D. fragilis and Blastocystis sp. in M. domestica.

Subtype-host patterns and genetic differentiation of Blastocystis sp. in the Philippines

Blastocystis sp. is a gastrointestinal protozoan commonly encountered in humans and animals. Specificity to certain hosts may be associated with 38 known subtypes (STs) and 8 nonmammalian and avian STs (NMASTs). This can be determined by analyzing ST-host associations, ST-allele data, genetic variability analyses, and fixation index (FST) with sufficient data present. Thus, newly acquired and previously published data on Blastocystis sp. STs and NMASTs from the Philippines were compiled to determine the following: (1) ST-host associations, (2) ST-allele diversity per ST in certain hosts/sources, (3) intrasubtype diversity of certain STs found in different hosts using genetic variability analysis, and (4) comparison of similarities between specific ST populations to determine if these are the same circulating populations using FST. A total of 448 samples subtyped using both sequence-tagged site primers and the 600-bp barcoding region of the Blastocystis sp. SSU rRNA gene were analyzed in this study. Patterns of association for the Philippine samples were similar to those from neighboring Southeast Asian countries and around the world: ST1-ST4 were found in humans but ST3 was the most common, ST5 were found in pigs, and ST6 and ST7 were found in poultry. Blastocystis sp. from humans are mostly the same ST alleles (ST3 allele 34 and ST1 allele 4) while 3-5 ST alleles were found in the most common STs in pigs, macaques, and poultry. Also, ST1, ST3, ST5, and NMAST I are undergoing population expansion according to genetic variability analyses through possible addition of new alleles based on ST-allele diversity. Moreover, FST shows the same circulating population of ST1 in humans, pigs, and water indicating a possible waterborne route of cross-transmission. In contrast, ST3 found in humans possibly come from the same circulating population and is genetically distinct from those in nonhuman sources.

Molecular Prevalence and Subtypes Distribution of Blastocystis spp. in Humans of Latin America: A Systematic Review

Blastocystis spp. are among the few enteric parasites with a prevalence that can reach up to approximately 80% in communities of developing countries. This systematic review updates and summarizes available literature on the molecular prevalence and subtype distribution of Blastocystis spp. in Latin American people. This work follows the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The literature revised covers from 1 January 2015 to 6 October 2023 in seven different scientific databases, and the material was selected through inclusion and exclusion criteria. According to data found in the 36 selected articles, the prevalence of Blastocystis spp. in Latin America ranged between 5.8% (Bolivian rural communities) and 94.0% (Colombian general public). Generally, genomic DNA was extracted from approximately 200 mg fecal sediments using commercial kits, such as the QIAamp Stool Mini Kit (QIAGEN, Hilden, Germany) or the Norgen Stool DNA Isolation Kit (Norgen Biotek Corporation, Thorold, ON, Canada). Subtype-specific primers (such as the couple of primers BhRDr-RD5) developed from unique sequences of the SSU rRNA gene were applied to Blastocystis subtyping. Ten specific subtypes (STs) were found as well as various mixed infections, and the most circulating Blastocystis STs were in the order ST3, ST1, ST2, and ST4. The most recent data about Blastocystis spp. molecular epidemiology and the STs in communities of Latin America are limited to studies from specific countries. Novel scientific data from the other countries are required to obtain a complete picture and truly understand the distribution and prevalence of Blastocystis spp. and the STs.

Prevalence and genetic diversity of Blastocystis sp. among autochthonous and immigrant patients in Italy

The prevalence of Blastocystis sp., its genetic diversity and the distribution of circulating subtypes (STs) were molecularly investigated in a cohort of autochthonous and immigrant patients with gastrointestinal symptoms hospitalized over the period February 2022-June 2023 at the Policlinico Ospedaliero-Universitario "Riuniti", Foggia, in Southern Italy. The population variables, including patient geographical origin, gender and age classes were reported. Out of the 927 investigated patients, 36 (3.9%) were positive for Blastocystis sp. A statistically significant association with African origin and age classes >18 years old was found. ST1 (allele 4), ST2 (alleles 9, 13), ST3 (alleles 34, 36) and ST4 (allele 92) were the subtypes detected with a different distribution between autochthonous and immigrant patients. Co-infections with enteric protozoa such as Giardia duodenalis and Dientamoeba fragilis, pathogenic bacteria as Clostridioides difficile, Campylobacter jejuni and Aeromonas sp. and viral infections such as Norovirus were found in 33% of cases. This is the first study of Blastocystis sp., its circulating subtypes and allele variability among patients with different geographical origin in an area of Southern Italy, in the Central Mediterranean, characterized by high immigrant pressure. These results provide baseline data to better investigate a potential interaction between Blastocystis sp. and other risk factors in patients with gastrointestinal symptoms.

The impact of chlorine, ultraviolet-C, and microwave treatment on the survivability of Blastocystis sp. cysts

Blastocystis sp. is a common widely distributed gut protozoan, with water transmission identified as one of its transmission routes. This study aimed to investigate the effect of chlorine, ultraviolet (UV)-C, and microwave (MW) treatments on the in vitro viability of cysts of Blastocystis sp. Purified Blastocystis sp. cysts were molecularly subtyped. Viable cysts were subjected to different free chlorine concentrations (1, 2, and 4 ppm), different doses of UV-C (5.13, 10.26, 20.52, and 40.47 mJ/cm2), and MW irradiation times (10, 15, 30, and 45 s). Viability reduction percentage, log10 inactivation, and micrometre-based optical microscopy examined cyst number and appearance after each disinfection trial. The three disinfectants' efficacy and application conditions were assessed. The analysed isolates of Blastocystis cysts were subtype 3, possessed varying sizes and shapes, but two identical genomes. The cysts of Blastocystis sp. were resistant to chlorine at all doses and exposure durations tested. UV-C at a dose of 40 mJ/cm2 and MW treatment for 15 s were able to completely disinfect the cysts. The MW was the most effective disinfectant against Blastocystis cysts based on all evaluated factors. MW irradiation is the most efficient water treatment method for eradicating Blastocystis cysts in an easy and safe manner.

Metataxomics reveals Blastocystis subtypes mixed infections in Colombian children

Blastocystis sp., is an intestinal protist with a broad host range and a high prevalence in human populations worldwide, even in developed Western countries. The publication of conflicting evidence has divided the scientific community about the pathogenic role of this parasite. Even though, genetic studies on Blastocystis sp. revealed associations between genotypes and different pathogenic profiles. Conventionally, the detection of this parasite is based on microscopic or PCR methods, which offer meager or null performance in detecting mixed infections. In this work, we applied a metataxonomic NGS approach targeting the V4 region of the eukaryotic SSU-rRNA gene and classical phylogenetic methods. This approach allowed us to detect Blastocystis sp. in stool samples from infected children living in an urban setting in the city of Medellin attending the same daycare center. Phylogenetic analysis identified the subtypes present in the children as ST1, ST2, and ST3. Besides, mixed infections of subtypes ST1 + ST3 were spotted in 16% of the analyzed stool samples.

Identification of Blastocystis sp. in school children from a rural Mexican village: subtypes and risk factors analysis

Blastocystis sp. is a common eukaryotic microorganism that colonizes the intestinal tract of several animals, including humans, although its role as a pathogen is still unclear. In the present study, we report the prevalence and risk factors associated with Blastocystis infection in scholars from a rural community in Mexico. A cross-sectional observational study was carried out on schoolchildren aged 3 to 15 years old; fecal samples were analyzed by culture, Faust technique, and molecular analysis. In addition, a structured questionnaire was applied to identify possible risk factors. Of the 177 samples obtained, Blastocystis sp. was the microorganism that presented the highest frequency (n=78, 44%), and included the following subtypes (STs): ST1 (n=43, 56.5%), ST2 (n=18, 23.6%), and ST3 (n=15, 19.7%); Blastocystis STs were not identified in two cases. No associating factors were found between Blastocystis infection or among STs vs. symptoms. During bivariate analysis, no statistically significant risk factors were found, except for the variable of "eating sweets, snacks, and handmade food on the way home" (p=0.04). Therefore, it is plausible to conclude that schoolchildren become infected with Blastocystis sp. mainly outside their homes, perhaps by eating contaminated handmade food on their way to or from school; however, this variable should be evaluated in detail in future studies.

Circulation and colonisation of Blastocystis subtypes in schoolchildren of various ethnicities in rural northern Thailand

Blastocystis is a protist of controversial pathogenicity inhabiting the gut of humans and other animals. Despite a century of intense study, understanding of the epidemiology of Blastocystis remains fragmentary. Here, we aimed to explore its prevalence, stability of colonisation and association with various factors in a rural elementary school in northern Thailand. One hundred and forty faecal samples were collected from 104 children at two time points (tp) 105 days apart. For tp2, samples were also obtained from 15 animals residing on campus and seven water locations. Prevalence in children was 67% at tp1 and 89% at tp2, 63% in chickens, 86% in pigs, and 57% in water. Ten STs were identified, two of which were shared between humans and animals, one between animals and water, and three between humans and water. Eighteen children (out of 36) carried the same ST over both time points, indicating stable colonisation. Presence of Blastocystis (or ST) was not associated with body mass index, ethnicity, birth delivery mode, or milk source as an infant. This study advances understanding of Blastocystis prevalence in an understudied age group, the role of the environment in transmission, and the ability of specific STs to stably colonise children.

Blastocystis subtypes in raw vegetables from street markets in northern Thailand

Blastocystis is a stramenopile protist of controversial pathogenicity. The organism colonizes a broad range of vertebrate and invertebrate hosts. Blastocystis has also been found in the environment both in water and soil. Several routes of transmission have been proposed including human to human, animal to human, and via contaminated food and water. In recent years, the presence of Blastocystis in vegetables has started to be explored. However, most studies have focused on microscopic detection. Moreover, works of this type from Asia are barely available. Hence, the aim of this preliminary study was to examine the occurrence of Blastocystis in raw vegetables sold in markets in northern Thailand. Fresh produce (n = 20) commonly used in Thai cuisine (Lanna) was purchased from two street markets and screened for Blastocystis using qPCR. Blastocystis was detected in 45% of the samples with the dominant subtype being ST3. Produce growing underground, such as galangal, carrot, and beetroot, were positive for the organism suggesting soil or inadequately composted manure as the source of contamination. To our knowledge, our study is the first to perform subtyping of Blastocystis in vegetables. Our results hint toward fresh produce being a, as yet, not widely explored, transmission route of Blastocystis in the studied community. Looking forward, large-scale investigations on the prevalence of this and other organisms under the One Health umbrella should be undertaken.

Resistance of Blastocystis to chlorine and hydrogen peroxide

Blastocystis is a ubiquitous, widely distributed protist inhabiting the gastrointestinal tract of humans and other animals. The organism is genetically diverse, and so far, at least 28 subtypes (STs) have been identified with ST1-ST9 being the most common in humans. The pathogenicity of Blastocystis is controversial. Several routes of transmission have been proposed including fecal-oral (e.g., zoonotic, anthroponotic) and waterborne. Research on the latter has gained traction in the last few years with the organism having been identified in various bodies of water, tap water, and rainwater collection containers including water that has been previously filtered and/or chlorinated. Herein, we assessed the resistance of 11 strains maintained in culture, spanning ST1-ST9 to various chlorine and hydrogen peroxide concentrations for 24 h, and performed recovery assays along with re-exposure. Following the treatment with both compounds, all subtypes showed increased resistance, and viability could be visualized at the cellular level. These results are hinting at the presence of mechanism of resistance to both chlorine and hydrogen peroxide. As such, this pilot study can be the platform for developing guidelines for water treatment processes.

Blastocystis occurrence in water sources worldwide from 2005 to 2022: a review

There has been increasing interest in the study of Blastocystis in the last two decades. Many studies have been carried out in human and animal hosts including environmental sources, but there is little or no information on the occurrence of Blastocystis in water sources worldwide. Therefore, this study aimed at assessing the occurrence of Blastocystis in water sources across the world from 2005 to 2022, noting the method of detection and the distribution of the subtypes from various water sources. A literature search was performed on internet-based databases including Google search, PubMed, Scopus, and Web of Science. Upon application of the criteria for inclusion, 25 articles revealing the occurrence of Blastocystis in water sources in 15 countries were included in the review. Blastocystis occurrence varies across water sources ranging from 0% in a drinking water source in Venezuela to 100% in rivers; well water, stored water, and fishpond in Nepal and Malaysia; and fountain water, irrigation water, and rainwater in Italy, Spain, and Thailand. The occurrence of the parasite was significantly associated with the coliform count, temperature, conductivity, dissolved oxygen, turbidity, total dissolved solids, and chemical oxygen demand. A total of 11 Blastocystis subtypes were identified in water sources worldwide, namely, ST1-ST8, ST10, ST23, and ST26 in which ST1 and ST3 were the most prevalent subtypes. Considering the importance of Blastocystis as a waterborne parasite, the subtype distribution and morphological distinction in water sources need to be carried out using molecular and electron microscopic techniques. Existing studies have covered only about 10% of the world's countries.

Global prevalence and subtype distribution of Blastocystis sp. in rodents, birds, and water supplies: A systematic review and meta-analysis

Animals such as rodents and birds may play a key role in the distribution of Blastocystis sp., either as introducers of the parasite into the water or as receptors of an infection already established in the water. Hence, we aimed to evaluate the prevalence and subtype distributions of Blastocystis sp. in rodents, birds, and water supplies at a global scale through a systematic review and meta-analysis approach. The standard protocol of preferred reporting items for systematic reviews and meta-analyses (PRISMA) statements were applied. Eligible prevalence studies on Blastocystis sp. in rodents, birds, and water supplies, published between 1 January 2000 and 20 January 2022 were collected using a systematic literature search in online databases (Scopus and Web of Science) and search engines (PubMed and Google Scholar). Inclusion and exclusion criteria were followed. The point estimates and 95% confidence intervals (CI) were calculated using a random-effects model. The variances between studies (heterogeneity) were computed by I2 index. In total, 20 articles (24 datasets) for birds, 18 articles (18 datasets) for rodents, and 10 articles (12 datasets) for water supply were included for the final meta-analysis. The pooled prevalence of Blastocystis sp. in birds, rodents, and water was estimated to be 29% (95% CI 12-47%), 18% (95% CI 12-23%), and 10% (95% CI 6%-15%), respectively. Considering the subtypes, Blastocystis sp. with subtypes ST7 in birds, ST4 in rodents, and ST1 in water supplies were the highest reported subtypes. The present results highlight the role of birds, rodents, and water as a reservoir for human-infected Blastocystis sp. Therefore, this global estimate could be beneficial for preventive and control measures.