Viable blastocystis cysts in Scottish and Malaysian sewage samples

Epidemiology of Blastocystis Infection: A Review of Data from Poland in Relation to Other Reports

Blastocystis is a common gut protist of humans and various animals worldwide, with a high level of genetic diversity. Neither its zoonotic potential and transmission routes nor its pathogenicity are fully known. This fact, and the fact that Blastocystis is the most abundant eukaryote in human faeces, raises the question of its relevance to public health. Here, we summarise (in relation to other reports) the results of studies on the prevalence and genotypic variation of Blastocystis, which were carried out in animals, humans, and in water environments in Poland. In humans, the prevalence ranged between 0.14 and 23.6%, in some animals reached 58.97%, and in water environments was 5.1%. Seven subtypes were identified in humans (ST1-ST4, ST6, ST7, and ST9), of which ST3 was the most common. Among animals (wild, livestock, and pet animals), eleven STs were identified, with differential host specificity. Humans and animals shared ST1, ST2, ST3, ST6, and ST7, while ST1 and ST3 were present in humans, animals, and water sources. These observations indicate the possibility of Blastocystis transmission between animals and humans. Further studies should be continued in search of the sources and transmission routes of Blastocystis in order to prevent the spread of infections among humans and animals.

Blastocystis infection among diarrhea outpatients in Ningbo, Southeast China: A potential zoonotic health threat

BACKGROUND

Blastocystis is one of the important zoonotic parasites which can infect humans and various animals worldwide and has become a growing global public health concern. The study aims to obtain the data of Blastocystis infection and the information of the genetic characteristic.

METHODS

In the present study, 489 fecal samples were collected from diarrhea outpatients in Ningbo, Zhejiang province, and were examined the presence of Blastocystis by polymerase chain reaction combined with sequencing.

RESULTS

A total of 10 samples (2.04%, 10/489) were positive for Blastocystis with no significant difference among sex and age groups, respectively. Eight samples were successfully sequenced, and five zoonotic ST3 and three zoonotic ST1 with two new sequences were identified.

CONCLUSIONS

We first demonstrated the occurrence of Blastocystis infection in diarrhea outpatients in Ningbo, with two zoonotic subtypes (ST1 and ST3) and two new sequences being characterized. Meanwhile, mixed infection of Blastocystis and E. bieneusi was found which indicates the importance of investigation of multiple parasites. Finally, more extensive studies will be needed to better understand the transmission of Blastocystis at human-animal-environment interface and provide evidence for the development of one health strategies for the prevention and control of such diseases.

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.

Prevalence of Blastocystis sp. in freshwater fishes, poultry, and caprine from Penang, Malaysia

Blastocystis is an enigmatic intestinal protist of humans and many animals. There is growing interest in its potential as an enteric pathogen, and the possible role of domestic and in-contact animals as reservoirs for human infection. The purpose of this study was to determine the prevalence of Blastocystis infection in fishes, poultry, and caprine in Penang, Malaysia. A total of 353 faecal samples/intestinal contents, consisting of 123 intestinal contents from freshwater fishes, 96 intestinal contents of commercially barn-reared chickens, 84 intestinal contents of barn-reared quails, and 50 faecal samples of caprine (29 from meat goats and 21 from dairy goats) were collected. Faecal sample/intestinal content from each animal was subjected to in-vitro cultivation method using Jones' medium supplemented with 10% horse serum. The respective colonization frequencies for dairy and meat goats were 47.6% and 31.0%, whereas 26.1% was recorded for chickens and 16.7% for quails. None of the freshwater fishes were found infected with Blastocystis. The organism was most commonly seen as spherically shaped vacuolated forms and cell diameter was significantly larger in poultry than in caprine. For further studies, molecular characterization of Blastocystis in poultry and livestock animals in the study area is highly recommended.

Blastocystis in tap water of a community in northern Thailand

Blastocystis is the most common protist in the gut of humans and other animals having global distribution. Occasionally, this organism has also been reported in the environment. Transmission to humans occurs via the fecal-oral route, while water also comprises a transmission route. Blastocystis has been commonly found in rivers, lakes, and wells. Nonetheless, there is limited data about the prevalence and genetic diversity of Blastocystis in tap water. The main aim of this study was to examine the presence of Blastocystis subtypes in tap water (n=20) in a community in northern Thailand. Molecular characterization using the small subunit ribosomal RNA was used to screen for Blastocystis and identify the diversity of subtypes in samples. The overall prevalence was 30% with only subtype three (ST3) encountered in the tap water. These results indicate that tap water has a potential role in the transmission of this subtype in the studied community. Further investigations should focus on expanding sampling to include additional housing complexes and screening for Blastocystis in humans who are exposed to this water.

Prevalence and Associated Risk Factors of Intestinal Parasitic Infections among Patients Visiting a Referral Hospital in Tehran Province, Iran

BACKGROUND

Intestinal parasitic infections (IPIs) are still considered a public health problem of mankind, particularly in immunocompromised patients. We aimed to determine the prevalence of IPIs with an emphasis on immunocompromised patients in a referral hospital in Tehran Province, Iran.

METHODS

In this cross-sectional study, 442 fecal specimens were collected randomly from patients, referred to Baqiyatallah Hospital in Tehran Province, Iran from May to September 2020. The collected specimens were examined using wet-mount, trichrome and modified Ziehl-Neelsen staining, formalin-ether concentration, and agar plate culture.

RESULTS

The prevalence of IPIs was found 17.0% (95% CI: 13.6-20.8%). The prevalence of protozoan parasites (16.3%; 95% CI: 13.0-20.1%) was significantly higher than helminthic parasites (0.7%; 95% CI: 0.1-2.0%). Blastocystis spp., Giardia lamblia, and Entamoeba coli were the most common intestinal protozoan with a prevalence of 12.2%, 1.6%, and 1.4%, respectively. E. histolytica/E. dispar/E. moshkovskii, Iodamoeba bütschlii, Cryptosporidium spp., Chilomastix mesnili as protozoan species and Hymenolepis nana, Dicrocoelium dendriticum, and Ascaris lumbricoides as helminthic species were the other detected parasites. Multiple logistic regression revealed a significant association of IPIs infections with stool consistency and the status of immune system.

CONCLUSION

The prevalence of IPIs among the patients who are immunocompromised was significantly higher than immunocompetent patients (P< 0.05). Periodic stool examinations for screening of IPIs should be included as a part of routine medical check-up in these patients.

First report of Blastocystis sp. subtypes in natural water bodies in north-western Poland: a one-year monitoring

Studies on the presence of Blastocystis subtypes in water samples are far less numerous compared with stool samples. The main aim of this study was to examine the occurrence of Blastocystis subtypes in 36 natural water bodies in north-western Poland in the period from winter 2009 to autumn 2010. Single PCR with the use of Blast 505-532/Blast 998-1017 set of primers was used to detect Blastocystis DNA in the obtained water samples. Sequencing of the obtained amplicons revealed the presence of ST1 and ST3 subtypes in five of the 36 (13.9%) examined water bodies within 1 year period. Further examinations with the use of new samples are needed in order to check if Blastocystis occurs in the examined water bodies at the present time, however, the risk of infection should be taken into consideration.

Blastocystis One Health Approach in a Rural Community of Northern Thailand: Prevalence, Subtypes and Novel Transmission Routes

Blastocystis is the most commonly found eukaryote in the gut of humans and other animals. This protist is extremely heterogeneous genetically and is classified into 28 subtypes (STs) based on the small subunit ribosomal RNA (SSU rRNA) gene. Numerous studies exist on prevalence of the organism, which usually focus on either humans or animals or the environment, while only a handful investigates all three sources simultaneously. Consequently, understanding of Blastocystis transmission dynamics remains inadequate. Our aim was to explore Blastocystis under the One Health perspective using a rural community in northern Thailand as our study area. We surveyed human, other animal and environmental samples using both morphological and molecular approaches. Prevalence rates of Blastocystis were 73% in human hosts (n = 45), 100% in non-human hosts (n = 44) and 91% in environmental samples (n = 35). Overall, ten subtypes were identified (ST1, ST2, ST3, ST4 ST5, ST6, ST7, ST10, ST23, and ST26), eight of which were detected in humans (ST1, ST2, ST3, ST4, ST5, ST7, ST10, and ST23), three in other animals (ST6, ST7, and ST23), while seven (ST1, ST3, ST6, ST7, ST10, ST23, and ST26) were found in the environment. In our investigation of transmission dynamics, we assessed various groupings both at the household and community level. Given the overall high prevalence rate, transmission amongst humans and between animals and humans are not as frequent as expected with only two subtypes being shared. This raises questions on the role of the environment on transmission of Blastocystis. Water and soil comprise the main reservoirs of the various subtypes in this community. Five subtypes are shared between humans and the environment, while three overlap between the latter and animal hosts. We propose soil as a novel route of transmission, which should be considered in future investigations. This study provides a thorough One Health perspective on Blastocystis. Using this type of approach advances our understanding on occurrence, diversity, ecology and transmission dynamics of this poorly understood, yet frequent gut resident.

Subtype analysis and prevalence of mixed subtype infection of Blastocystis in farmed pigs from Chiba Prefecture, Japan

Blastocystis is an intestinal eukaryotes found in a wide range of animals and in the human population globally. Blastocystis is reported in domestic pigs, with subtype (ST) 5 being the dominant ST, followed by ST1 and ST3. The common method used for ST identification in pigs is PCR-sequencing, which often results in underestimation of the prevalence of mixed infections. Here, we aimed to investigate the ST distribution and the prevalence of mixed ST infection of Blastocystis in pigs from Chiba Prefecture in eastern Japan. A total of 82 fecal samples positive for Blastocystis were collected from two different farms, A and B. PCR was performed with subtype-specific primers, ST1, ST2, ST3, and ST5. The prevalence of single ST5 infection was 37.8% (31/82), whereas mixed infection with ST5 and other STs was 57.3% (47/82). A high percentage of single ST5 infection was observed in sows, piglets, and weaners from farm A (13/15, 86.7%), whereas mixed infection of ST5 and other STs, ST1 and ST3, was observed in 3-5-month-old grower pigs (15/18, 83.3%). Similarly, in farm B, the majority of sows and piglets under 1 month of age showed a single ST5 infection (12/17, 70.6%), whereas weaner, grower, and finisher pigs showed mixed infections with ST5 and other STs, ST1, ST2 and ST3 (27/28, 96.4%). In domestic pigs, diet and rearing environment changes dramatically over the course of animal's lifetime, which may have caused this difference in the prevalence of mixed ST infection among different age groups.

Prevalence, subtypes and risk factors of Blastocystis spp. infection among pre- and perimenopausal women

Background

Blastocystis spp. are considered pathogenic or commensal organisms, although the majority of researchers suggest that these are neglected pathogens. The main aim of this study was to determine the prevalence and subtype distribution of Blastocystis spp. in pre- and perimenopausal women, with respect to socio-demographic (age and place of residence), and epidemiological factors, as well as drinking tap water, contact with domestic animals, traveling abroad, health status, and presence of gastrointestinal symptoms. Additionally, the objective was to compare hematological and biochemical parameters of Blastocystis spp. infected and uninfected women.

Methods

The study included 425 women aged 45–60. Their stool samples were examined microscopically and analyzed by a conventional polymerase chain reaction (cPCR).

Results

Blastocystis spp. were detected in 6.1% of pre- and perimenopausal women. Molecular analysis of the stool samples identified seven Blastocystis subtypes (ST1–ST4, ST6, ST7, and ST9). Blastocystis subtypes 2 and 3 were the most prevalent. The presence of Blastocystis spp. was not significantly related to socio-demographic and epidemiological factors. There were also no significant associations between Blastocystis spp. and blood parameters, or gastrointestinal symptoms.

Conclusion

This study complements the limited available data on the prevalence of Blastocystis spp. in pre- and perimenopausal women. It is also the first report showing the presence of Blastocystis subtype 9 in Poland.

Blastocystis in domesticated and wild mammals and birds

Blastocystis is a ubiquitous parasite that infects a broad range of vertebrate hosts including humans and domestic and wild animals. While human infections have been occasionally associated with gastrointestinal illnesses and/or urticaria, animal infections are not usually associated with disease. However, from a public health perspective, most subtypes isolated in humans have also been isolated from animals raising the question of the importance of animal reservoirs in the epidemiology of this parasite. The identification of Blastocystis in water supplies suggests water can be a potential vehicle in the transmission of this parasite not only for humans but also for animals. In addition, Blastocystis has been detected in retail fresh produce. Knowledge of this parasite has greatly expanded in the last two decades from simple microscopic observations to the application of molecular tools to explore Blastocystis taxonomy and epidemiology. This review provides a comprehensive overview of Blastocystis in animals highlighting the subtype diversity of this widespread and genetically diverse parasite in different animal groups. This information will be useful in understanding the current status of taxonomy, epidemiology, zoonotic potential, and public health importance of Blastocystis.

First molecular subtyping and phylogeny of Blastocystis sp. isolated from domestic and synanthropic animals (dogs, cats and brown rats) in southern Iran

BACKGROUND

Blastocystis sp. is a common intestinal protist that infects humans and many animals globally. Thus far, 22 subtypes (STs) have been identified in mammalian and avian hosts. Since various STs are common to humans and animals, it was suggested that some human infections might arise from zoonotic transmission. Therefore, the aim of this study was to assess the presence of Blastocystis sp. in domestic (dogs and cats) and synanthropic animals (rats) of Fars Province, Iran, and to genetically characterize the samples.

METHODS

A total of 400 fresh faecal samples from 154 dogs, 119 cats, and 127 rats were inspected by direct microscopy, Wheatley's trichrome staining, in vitro culture, and 18S rRNA gene nested-PCR. Finally, sequencing and phylogenetic analyses were performed.

RESULTS

Out of 400 samples, 47 (11.8%) and 61 (15.3%) samples were detected as positive by direct wet mount and culture, respectively. Molecular analysis detected a larger number of positive samples (n = 70, 17.5%): nested-PCR showed that 29 (18.8%) dogs, 21 (17.7%) cats, and 20 (15.8%) rats were infected by Blastocystis sp. Sequence analysis of positive samples indicated the presence of zoonotic STs in all investigated host species. Specifically, ST2 (allele 9), ST3 (allele 34), ST4 (allele 94), ST7 (allele 99), ST8 (allele 21), and ST10 (allele 152) were detected in dogs; ST1 (allele 2), ST3 (allele 34), ST4 (allele 94), ST10 (allele 152), and ST14 (allele 159) were detected in cats; and ST1 (allele 2), ST3 (allele 34), and ST4 (allele 92) were detected in rats.

CONCLUSIONS

Our data suggest that domestic dogs and cats can serve as possible reservoirs for in-contact humans, especially those who handle shelter-resident and client-owned animals. Moreover, rats as synanthropic animals can function as a potential source of human infections. Conversely, humans can act as a source of infections to animals. These results should be reinforced in future molecular epidemiological studies.

First Report on the Occurrence and Subtypes of Blastocystis in Pigs in Poland Using Sequence-Tagged-Site PCR and Barcode Region Sequencing

Blastocystis is an enteric microorganism commonly found in humans and animals worldwide. Its pathogenic role in humans and transmission patterns has not been fully explained. However, nine subtypes (ST1-8, ST12) are considered as potentially zoonotic. Studies from various regions of the world show that pigs are mainly infected with ST5. Although pigs are important farmed animals in Poland, the question of Blastocystis infection in these animals has not yet been investigated. Herein, 149 pig stool samples from 10 Polish pig farms were analyzed using sequence-tagged-site PCR and barcode region sequencing. The percentage of samples in which Blastocystis was identified using each method separately was similar: 38.25% and 37.58%, respectively. However, the percentage of positive results obtained by combining both methods was 46.97%, which means that, depending on the method used, the number of undetected samples varied between 8.72% and 9.39%. This shows the methodological limitations of up-to-date molecular approaches commonly used in Blastocystis research. A moderate infection rate (44.4-50%) observed in different pig age groups with a vital predominance of ST5 (94.28%) in every age group shows that pigs are a likely natural host of ST5. A small percentage of mixed infections, namely ST5/ST1 (5.26%), ST5/ST3 (1.75%), and ST3/ST1 (1.75%), was observed only in animals of older age, suggesting that ST3 and ST1 can be acquired by pigs during contact with humans. This study provides the first data on the prevalence and Blastocystis subtypes (STs) distribution in pigs in Poland. The results also highlight the need for the development of new methods capable of detecting highly genetically diverse Blastocystis isolates and mixed infections.

Molecular genotyping of Blastocystis spp. in wild mammals from Mexico

Blastocystis spp. are common intestinal parasites found worldwide in humans and a wide range of animals. They exhibit extensive genetic diversity; currently, 17 subtypes (STs) and some groups called non-mammalian and avian STs (NMASTs) have been proposed. In addition, a large variety of animals have been reported as hosts of the parasite, and new hosts and STs are still being described. In this study, Blastocystis infection of wild animals in two sylvatic areas of Mexico was surveyed. Of one hundred twenty-four fecal samples, six were positive for Blastocystis: specifically, one sample from an opossum, one sample from a bat, and four samples from different species of rodents. ST4, ST17, and nucleotide sequences similar to Blastocystis lapemi were identified based on SSU rDNA sequences. To our knowledge, this is the first report to investigate species poorly or not previously evaluated for Blastocystis infection. Mammals having different niches and geographical distribution were infected with similar genetic type of Blastocystis, so that we suggest that local water or food sources could play an important role in Blastocystis transmission and ST maintenance in wild animals. Additionally, there are STs with scarce genetic variation, suggesting that they could be highly adapted to their hosts. These data contribute to our understanding of the host range and genetic diversity of Blastocystis.

Molecular analysis of Blastocystis sp. and its subtypes from treated wastewater routinely used for irrigation of vegetable farmlands in Iran

Treated wastewater samples were collected, filtered using sterile 47-mm cellulose nitrate membrane and DNA extracted from the filtered materials. The presence of Blastocystis sp. was confirmed via polymerase chain reaction (PCR) targeting the SSU rRNA gene of Blastocystis sp. in 5/12 of samples. Based on the subtype analysis after sequencing, 2, 2 and 1 of ST2, ST6 and ST8 were detected among the isolates, respectively. Furthermore, both ST6s were allele 139, alleles 11 and 138 were identified in ST2 and the only ST8 was allele 95. The phylogenetic tree showed that one of ST2 was clustered together with those ST2 that were already reported from humans and animals. The presence of Blastocystis sp. in treated wastewater can indicate the potential role of this type of water for irrigation in the transmission of pathogenic microorganisms to downstream farmlands.

Establishing a protocol for water sample processing for the detection of Blastocystis sp

This study was aimed at establishing a protocol for water sample processing for the detection of Blastocystis sp. using distilled water spiked with Blastocystis sp. cysts. The study established a protocol involving eight technical aspects, namely, storage temperature, storage duration, minimum water sample volume, optimum relative centrifugal force, centrifugation duration, minimum number of cyst for inoculation in Jones' medium and turn-around-time for the detection of vacuolar forms of Blastocystis sp. Results showed a minimum of 1.0 L water sample should be collected and processed on the same day. Otherwise, it should be stored at 4 °C and processed within 3 days. Water sample should be centrifuged at 1400×g for 10 min. For the isolation of Blastocystis sp. cysts, parasite pellet could be layered on top of Ficoll-Paque™ PLUS, centrifuged at 1400×g for 20 min and washed twice using 0.9% saline with centrifugation at 1400×g for 10 min. A minimum of 1 × 10⁵ cysts could then be inoculated in Jones' medium supplement with 10% horse serum, incubated at 37 °C and examined for any presence of vacuolar forms of Blastocystis sp. after 3 days of inoculation. A protocol for water sample processing for the detection of Blastocystis sp. has successfully been established. The protocol was validated using 106 various water samples. This protocol will be very useful in determining the extent of Blastocystis sp. contamination in water sources in order to identify the seriousness of contamination.

Zoonotic and genetically diverse subtypes of Blastocystis in US pre-weaned dairy heifer calves

Blastocystis is an emerging zoonotic pathogen with global distribution. However, limited data exist on the prevalence and genetic diversity of Blastocystis in the USA and in food animals. We conducted the first large-scale molecular investigation of Blastocystis in the USA by testing 2539 fecal samples from dairy heifer calves from 13 states. Blastocystis was detected in 73 (2.9%) fecal samples and in 10 of the 13 tested states. Molecular characterization showed a wide diversity of subtypes. Eleven subtypes were identified, seven previously reported (ST-3, ST-4, ST-5, ST-10, ST-14, ST-17, and ST-21) and four potentially novel subtypes (named ST-23 to ST-26). Zoonotic subtypes 3, 4, and 5 were found in 67% (49) of the positive specimens in this population. Our results suggest that cattle could serve as reservoirs of infection for humans and other domestic animals highlighting the potential risk of zoonotic transmission for Blastocystis.

Prevalence and risk factors of Blastocystis infection among underprivileged communities in rural Malaysia

OBJECTIVES

To determine the prevalence and risk factors of Blastocystis among underprivileged communities living in rural Malaysia.

METHODS

This cross-sectional study was conducted among 253 participants aged between 1 and 85 years. Stool samples were examined using Wheatley's trichrome stain after in-vitro cultivation in Jones' medium to detect the presence of Blastocystis. Information pertaining to the demography, socioeconomic and environment were collected using pre-validated questionnaires.

RESULTS

The total prevalence of Blastocystis infection was 40.7%. The multiple logistic regression analysis revealed that age ≥15 years (OR = 2.72; 95% CI = 1.47-5.04) and presence of infected family members (OR = 8.56; 95% CI = 4.47-16.38) were the significant risk factors associated with blastocystosis in these communities.

CONCLUSIONS

Blastocystosis is revealed through this study to be still prevalent among Orang Asli communities in rural Malaysia. The two main approaches that should be implemented by the public health authority in battling this infection would be the screening of other family members and giving treatment to the infected individuals. Moreover, it is imperative for health education on good personal and food hygiene practices are provided in order to reduce the morbidity and transmission of Blastocystis infection among the Orang Asli in their communities meaningfully.

Occurrence of Blastocystis sp. in water catchments at Malay villages and Aboriginal settlement during wet and dry seasons in Peninsular Malaysia

In the tropics, there are too few studies on isolation of Blastocystis sp. subtypes from water sources; in addition, there is also an absence of reported studies on the occurrence of Blastocystis sp. subtypes in water during different seasons. Therefore, this study was aimed to determine the occurrence of Blastocystis sp. subtypes in river water and other water sources that drained aboriginal vicinity of highly endemic intestinal parasitic infections during wet and dry seasons. Water samples were collected from six sampling points of Sungai Krau (K1–K6) and a point at Sungai Lompat (K7) and other water sources around the aboriginal villages. The water samples were collected during both seasons, wet and dry seasons. Filtration of the water samples were carried out using a flatbed membrane filtration system. The extracted DNA from concentrated water sediment was subjected to single round polymerase chain reaction and positive PCR products were subjected to sequencing. All samples were also subjected to filtration and cultured on membrane lactose glucuronide agar for the detection of faecal coliforms. During wet season, Blastocystis sp. ST1, ST2 and ST3 were detected in river water samples. Blastocystis sp. ST3 occurrence was sustained in the river water samples during dry season. However Blastocystis sp. ST1 and ST2 were absent during dry season. Water samples collected from various water sources showed contaminations of Blastocystis sp. ST1, ST2, ST3 and ST4, during wet season and Blastocystis sp. ST1, ST3, ST8 and ST10 during dry season. Water collected from all river sampling points during both seasons showed growth of Escherichia coli and Enterobacter aerogenes, indicating faecal contamination. In this study, Blastocystis sp. ST3 is suggested as the most robust and resistant subtype able to survive in any adverse environmental condition. Restriction and control of human and animal faecal contaminations to the river and other water sources shall prevent the transmission of Blastocystis sp. to humans and animals in this aboriginal community.

Neglected waterborne parasitic protozoa and their detection in water

Outbreak incidents raise the question of whether the less frequent aetiological agents of outbreaks are really less frequent in water. Alternatively, waterborne transmission could be relevant, but the lack of attention and rapid, sensitive methods to recover and detect the exogenous stages in water may keep them under-recognized. High quality information on the prevalence and detection of less frequent waterborne protozoa, such as Cyclospora cayetanensis, Toxoplasma gondii, Isospora belli, Balantidium coli, Blastocystis hominis, Entamoeba histolytica and other free-living amoebae (FLA), are not available. This present paper discusses the detection tools applied for the water surveillance of the neglected waterborne protozoa mentioned above and provides future perspectives.

Prevalence, risk factors for infection and subtype distribution of the intestinal parasite Blastocystis sp. from a large-scale multi-center study in France

Background

Blastocystis sp. is the most common intestinal parasite of humans. Despite its potential public health impact, epidemiological data regarding the prevalence and molecular subtype distribution of Blastocystis sp. in Europe are rarely reported. Therefore, the first multi-center epidemiological survey performed in Europe was conducted in France to diagnose and subtype Blastocystis sp. and to identify risk factors for infection.

Methods

Stool samples from 788 patients were collected either in summer or winter in 11 hospitals throughout France together with patient data. All stool samples were tested for the presence of Blastocystis sp. by quantitative PCR targeting the SSU rDNA gene. Positive samples were sequenced to determine the distribution of the subtypes in our cohort. Statistical analyses were performed to identify potential risk factors for infection.

Results

Using quantitative PCR, the overall prevalence of Blastocystis sp. was shown to reach 18.1 %. The prevalence was significantly higher in summer (23.2 %) than in winter (13.7 %). Travellers or subjects infected with other enteric parasites were significantly more infected by Blastocystis sp. than non-travellers or subjects free of other enteric parasites, respectively. Different age-related epidemiological patterns were also highlighted from our data. The prevalence of Blastocystis sp. was not significantly higher in patients with digestive symptoms or diagnosed with chronic bowel diseases. Among symptomatic patients, Blastocystis sp. infection was significantly associated with abdominal pain. Gender, socioeconomic status, and immune status were not identified as potential risk factors associated with infection. Among a total of 141 subtyped isolates, subtype 3 was predominant (43.3 %), followed by subtype 1 and subtype 4 (20 %), subtype 2 (12.8 %), subtype 6 and subtype 7 (2.1 %). No association between ST and clinical symptoms was statistically evidenced.

Conclusions

A high prevalence of Blastocystis sp. infection was found in our French patient population. Seasonal impact on the prevalence of Blastocystis sp. was highlighted and recent travels and age were identified as main risk factors for infection. Most cases were caused by subtypes 1 to 4, with a predominance of subtype 3. Large variations in both prevalence and ST distribution between hospitals were also observed, suggesting distinct reservoirs and transmission sources of the parasite.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1776-8) contains supplementary material, which is available to authorized users.

Predominance of Blastocystis sp. Infection among School Children in Peninsular Malaysia

Background

One of the largest cross-sectional study in recent years was carried out to investigate the prevalence of intestinal parasitic infections among urban and rural school children from five states namely Selangor, Perak, Pahang, Kedah and Johor in Peninsula Malaysia. This information would be vital for school authorities to influence strategies for providing better health especially in terms of reducing intestinal parasitism.

Methods and Principal Findings

A total of 3776 stool cups was distributed to 26 schools throughout the country. 1760 (46.61%) responded. The overall prevalence of intestinal parasitic infection in both rural and urban areas was 13.3%, with Blastocystis sp (10.6%) being the most predominant, followed by Trichuris trichiura (3.4%), Ascaris lumbricoides (1.5%) and hook worm infection (0.9%). Only rural school children had helminthic infection. In general Perak had the highest infection (37.2%, total, n = 317), followed by Selangor (10.4%, total, n = 729), Pahang (8.6%, total, n = 221), Kedah (6.2%, total, n = 195) and Johor (3.4%, total, n = 298). School children from rural schools had higher infection (13.7%, total, n = 922) than urban school children (7.2%, total, n = 838). Subtype (ST) 3 (54.3%) is the most predominant ST with persons infected with only ST1 and ST3 showing symptoms. Blastocystis sp infection significantly associated with low household income, low parent’s education and presence of symptoms (p<0.05).

Conclusion

It is critical that we institute deworming and treatment to eradicate the parasite especially in rural school children.

Epidemiologic Study of Blastocystis Infection in an Urban Community in the Philippines

Blastocystis has been considered as the most common intestinal parasite in humans and has an augmented impact on public health. However, the prevalence of this parasite in the Philippines has not been determined. To contribute to a better understanding of the epidemiology of this infection, a cross-sectional study aimed at providing the first documented data on the prevalence and correlates, sociodemographic factors, hygiene practices, source of water supply, and dog ownership, associated with Blastocystis infection was carried out in randomly selected communities at Pateros, Metro Manila. Fecal samples from respondents were collected and cultured in diphasic agar medium for 3–7 days and examined using light microscopy. Of the 1,271 respondents, 12.98% (95% CI: 11.13–14.83) were detected positive for Blastocystis. Among the correlates of Blastocystis infection, dog ownership was found significantly associated as confirmed by multivariate analysis. Therefore, this factor should be considered in information to create awareness about Blastocystis and to prevent and control Blastocystis infection in particular and diarrheal diseases in general. Further studies using molecular approaches to distinguish subtype and to determine genetic characteristics of isolates from humans and dogs are recommended to analyze their relationship and provide more conclusive evidence of cross-transmission.

Blastocystis, an unrecognized parasite: an overview of pathogenesis and diagnosis

Blastocystis sp. is among the few enteric parasites with a prevalence that often exceeds 5% in the general population of industrialized countries and can reach 30-60% in developing countries. This parasite is frequently found in people who are immunocompromised (patients with human immunodeficiency virus/acquired immunodeficiency syndrome or cancer) and a higher risk of Blastocystis sp. infection has been found in people with close animal contact. Such prevalence in the human population and the zoonotic potential naturally raise questions about the impact of these parasites on public health and has increased interest in this area. Recent in vitro and in vivo studies have shed new light on the pathogenic power of this parasite, suggesting that Blastocystis sp. infection is associated with a variety of gastrointestinal disorders, may play a significant role in irritable bowel syndrome, and may be linked with cutaneous lesions (urticaria). Despite recent significant advances in the knowledge of the extensive genetic diversity of this species, the identification of extracellular proteases as virulence factors and the publication of one isolate genome, many aspects of the biology of Blastocystis sp. remain poorly investigated. In this review, we investigate several biological aspects of Blastocystis sp. (diversity and epidemiology, diagnosis tools and pathophysiology). These data pave the way for the following challenges concerning Blastocystis sp. research: deciphering key biological mechanisms and pathways of this parasite and clarification of its clinical impact in humans.

Children of Senegal River Basin show the highest prevalence of Blastocystis sp. ever observed worldwide

Background

Blastocystis sp. is currently the most common intestinal protist found in human feces and considered an emerging parasite with a worldwide distribution. Because of its potential impact in public health, we reinforced the picture of Blastocystis sp. prevalence and molecular subtype distribution in Africa by performing the first survey of this parasite in Senegal.

Methods

Stool samples from 93 symptomatic presenting with various gastrointestinal disorders or asymptomatic children living in three villages of the Senegal River Basin were tested for the presence of Blastocystis sp. by non-quantitative and quantitative PCR using primer pairs targeting the SSU rDNA gene. Positive samples were subtyped to investigate the frequency of Blastocystis sp. subtypes in our cohort and the distribution of subtypes in the symptomatic and asymptomatic groups of children.

Results

By the use of molecular tools, all 93 samples were found to be positive for Blastocystis sp. indicating a striking parasite prevalence of 100%. Mixed infections by two or three subtypes were identified in eight individuals. Among a total of 103 subtyped isolates, subtype 3 was most abundant (49.5%) followed by subtype 1 (28.2%), subtype 2 (20.4%) and subtype 4 (1.9%). Subtype 3 was dominant in the symptomatic group while subtypes 1 and 2 were detected with equal frequency in both symptomatic and asymptomatic groups. The distribution of subtypes was compared with those available in other African countries and worldwide. Comparison confirmed that subtype 4 is much less frequently detected or absent in Africa while it is commonly found in Europe. Potential sources of Blastocystis sp. infection including human-to-human, zoonotic, and waterborne transmissions were also discussed.

Conclusions

The prevalence of Blastocystis sp. in our Senegalese population was the highest prevalence ever recovered worldwide for this parasite by reaching 100%. All cases were caused by subtypes 1, 2, 3 and 4 with a predominance of subtype 3. More than half of the children infected by Blastocystis sp. presented various gastrointestinal disorders. Such high prevalence of blastocystosis in developing countries makes its control a real challenge for public health authorities.

Blastocystis sp.: waterborne zoonotic organism, a possibility?

Background

Blastocystis sp. is a common intestinal parasite found in faecal sample surveys. Several studies have implicated human-to-human, zoonotic and waterborne transmissions by Blastocystis sp. However, there has been no study providing evidence interlinking these three transmissions in a community. We have previously shown a high prevalence of Blastocystis sp. subtype 4 amongst village dwellers in Bahunipati, Nepal, and the present study extends the observation to assess if the same subtype of Blastocystis sp. occurs in animals they rear and rivers they frequent.

Methods

Faecal samples were collected from 65 animals. Four river water samples were collected from two rivers. Faecal samples were examined using in vitro cultivation. Blastocystis sp. from animal faecal and river samples were genotyped using seven subtype-specific sequence tagged site (STS) primer-polymerase chain reaction (PCR).

Results

Blastocystis sp. infected 15.4% animals with subtype 4 being the predominant genotype (40.0%). Both rivers were contaminated with Blastocystis sp. subtype 1 and subtype 4, which were also detected in humans living in the same village in our previous study. Blastocystis sp. subtype 4 that was detected in buffalo and pigs was also found in the respective family members that reared these animals.

Conclusions

This unusually high prevalence of Blastocystis subtype 4 found in village dwellers was also found to be pervasive in the animals they reared and the rivers they frequented implying a strong possibility of waterborne zoonosis for Blastocystis sp.

Detection and transmission of Dientamoeba fragilis from environmental and household samples

Dientamoeba fragilis is a commonly occurring pathogenic protozoan often detected at higher rates in stool samples than Giardia intestinalis. However, little is known about its life cycle and mode of transmission. A total of 210 environmental and household samples were examined for the presence of D. fragilis by culture and polymerase chain reaction. Of 100 environmental samples, D. fragilis was detected only in untreated sewage. In the household samples D. fragilis was detected in 30% of household contacts tested and was not detected in any domestic pets. This study provides evidence that environmental transmission of D. fragilis is unlikely and that pets played no role in transmission of the disease in this study. Direct transmission from infected persons is the most likely mode of transmission for D. fragilis. The study also highlights the need for household contacts to be screened, given the propensity of close contacts to become infected with the organism.

Development and evaluation of a real-time PCR assay for detection and quantification of blastocystis parasites in human stool samples: prospective study of patients with hematological malignancies

Blastocystis anaerobic parasites are widespread worldwide in the digestive tract of many animal species, including humans. Epidemiological Blastocystis studies are often limited by the poor sensitivity of standard parasitological assays for its detection. This report presents a highly sensitive real-time quantitative PCR (qPCR) assay developed to detect Blastocystis parasites in stool samples. The assay targets a partial sequence of the Blastocystis small ribosomal subunit (SSU) rRNA gene, allowing subtyping (ST) of Blastocystis isolates by direct sequencing of qPCR products. This qPCR method was assessed in a prospective study of 186 patients belonging to two cohorts--a group of 94 immunocompromised patients presenting hematological malignancies and a control group of 92 nonimmunocompromised patients. Direct-light microscopy and xenic in vitro stool culture analysis showed only 29% and 52% sensitivity, respectively, compared to our qPCR assay. Of the 27 (14.5%) Blastocystis-positive patients, 8 (4%) experienced digestive symptoms. No correlation was found between symptomatic patients and immune status, parasite load, or parasite subtypes, although subtyping of all isolates revealed a high (63.0%) prevalence of ST4. Two unexpected avian subtypes were found, i.e., ST6 and ST7, which are frequently isolated in Asia but rarely present in Western countries. In conclusion, this qPCR proved by far the most sensitive of the tested methods and allowed subtype determination by direct sequencing of qPCR products. New diagnostic tools such as the qPCR are essential for evaluating the clinical relevance of Blastocystis subtypes and their role in acute or chronic digestive disorders.

Eradication of Blastocystis carriage with antimicrobials: reality or delusion?

Metronidazole constitutes a mainstay in the antimicrobial therapy of intestinal protozoa, and is also traditionally considered first-line therapy in cases where there is a requirement to treat Blastocystis, a common protist of disputable clinical significance. Many compounds have been used in attempts to eradicate the parasite, and an accumulating body of data indicates that successful antimicrobial eradication of Blastocystis is far from straightforward. This review focuses on some issues that prevent us from reaching a clear understanding of how to eradicate Blastocystis based on chemotherapeutic intervention, by focusing on conflicting reports on the efficacy of metronidazole and other compounds and study design and data limitations. The review provides a comprehensive overview of antimicrobials used to target Blastocystis, and discusses issues pertaining to drug resistance, treatment failure, and reinfection. Finally, key methodological and molecular diagnostic tools that will assist in the generation of data required to improve current knowledge are identified and discussed.

Molecular characterization of Blastocystis isolates from zoo animals and their animal-keepers

Blastocystis is an enteric protist and one of the most frequently reported parasitic infections in humans and a variety of animal hosts. It has also been reported in numerous parasite surveys of animals in zoological gardens and in particular in non-human primate species. PCR-based methods capable of the direct detection of Blastocystis in faeces were used to detect Blastocystis from various hosts, including non-human primates, Australian native fauna, elephants and giraffes, as well as their keepers from a Western Australian zoo. Additional faecal samples were also collected from elephants and giraffes from four other zoos in Amsterdam (The Netherlands), Antwerp (Belgium), Melbourne and Werribee (Australia). Information regarding the general health and lifestyle of the human volunteers were obtained by questionnaire. Overall, 42% and 63% of animals and zoo-keepers sampled from the Western Australian zoo were positive for Blastocystis, respectively. The occurrence of Blastocystis in elephants and giraffes from other cities was similar. This is the first report of Blastocystis found in the elephant, giraffe, quokka, southern hairy nosed wombat and western grey kangaroo. Three novel and what appear to be highly host-specific subtypes (STs) of Blastocystis in the elephant, giraffe and quokka are also described. These findings indicate that further exploration of the genetic diversity of Blastocystis is crucial. Most zoo-keepers at the Perth Zoo were harbouring Blastocystis. Four of these zoo-keeper isolates were identical to the isolates from the southern hairy nosed wombat and five primate species.

Subtype analysis of Blastocystis isolates from symptomatic patients in Egypt

Blastocystis sp. has been described as the most common intestinal parasite in humans and has an increased impact in public health. To improve our understanding of the molecular epidemiology of this human-emerging parasite, we determined the Blastocystis subtypes (STs) and their relative frequency in Egyptian patients living in or in the vicinity of Cairo and presenting gastrointestinal symptoms. We obtained a total of 20 stool samples identified as positive for Blastocystis by microscopic examination of smears. Genotyping using partial small subunit ribosomal RNA gene analysis identified a total of 21 Blastocystis isolates corresponding to 19 single infections and one mixed infection (ST1 and ST3). Three STs were identified: ST3 was the most common ST in the present Egyptian population (61.90%) followed by ST1 (19.05%) and ST2 (19.05%). Together with previous studies carried out in different areas in Egypt, a total of five STs (ST1, ST2, ST3, ST4, and ST6) have been found in symptomatic patients. These data were compared to those available in the literature, and we underlined variations observed in the number and relative proportions of STs between and within countries. On the whole, it seemed that Blastocystis infection is likely not associated with specific STs even if some STs are predominant in the epidemiologic studies, but rather with a conjunction of factors in the course of infection including environmental risk and parasite and host factors.

Molecular epidemiology of human Blastocystis isolates in France

Blastocystis sp. is the most common eukaryotic parasite in the intestinal tract of humans. Due to its strong impact in public health, in this study, we determined the frequency of different Blastocystis subtypes in patients in France. We hypothesized on the mode of transmission and tested a possible relationship between the subtype and symptomatic status. We obtained a total of 40 stool samples identified as positive for Blastocystis by microscopic examination of smears. Participants consisted of 25 symptomatic and 15 asymptomatic patients, for whom clinical and parasitological data were collected. For nested-polymerase chain reaction and genotyping, DNA was extracted directly from fecal samples or from fecal cultures. Morphological forms observed in fecal cultures were uncorrelated with symptomatic status. Genotyping using partial small subunit rRNA gene analysis identified a total of 43 Blastocystis isolates corresponding to 37 single infections and three mixed infections by two different subtypes. These 43 isolates belonged to five subtypes (1, 2, 3, 4, and 7) with predominance of subtype 3 (53.5%). Patient symptomatic status was uncorrelated with Blastocystis subtype.

Molecular characterization of Blastocystis isolates from children and rhesus monkeys in Kathmandu, Nepal

To investigate the possible transmission of Blastocystis organisms between local rhesus monkeys and children in Kathmandu, Nepal, we compared the subtype (ST) and sequence of Blastocystis isolates from children with gastrointestinal symptoms and local rhesus monkeys. Twenty and 10 Blastocystis isolates were established from 82 and 10 fecal samples obtained from children and monkeys, respectively. Subtype analysis with seven sequence-tagged site (STS) primers indicated that the prevalence of Blastocystis sp. ST1, ST2 and ST3 was 20%, 20% and 60% in the child isolates, respectively. In contrast to human isolates, ST3 was not found in monkey isolates and the prevalence of ST1 and ST2 was 50% and 70%, respectively, including three mixed STs1 and 2 and one isolate not amplified by any STS primers, respectively. Since Blastocystis sp. ST2 has been reported as the most dominant genotype in the survey of Blastocystis infection among the various monkey species, sequence comparison of the 150bp variable region of the small subunit rRNA (SSU rRNA) gene was conducted among ST2 isolates of humans and monkeys. Sequence alignment of 24 clones developed from ST2 isolates of 4 humans and 4 monkeys showed three distinct subgroups, defined as ST2A, ST2B and ST2C. These three subgroups were shared between the child and monkey isolates. These results suggest that the local rhesus monkeys are a possible source of Blastocystis sp. ST2 infection of humans in Kathmandu.

Pursuing the clinical significance of Blastocystis--diagnostic limitations

The clinical significance of one of the most prevalent single-celled intestinal parasites worldwide, Blastocystis, remains unsettled. A plethora of clinical and epidemiological studies have been undertaken to generate data on its prevalence in different populations and investigate the role of the parasite as a cause of gastro- and extra-intestinal disease. In this article, we pinpoint limitations of studies that seek to determine the clinical significance of Blastocystis, based on shortcomings in our understanding of Blastocystis diagnosis and biology, and identify methodologies for further studies aimed at determining the molecular epidemiology and clinical impact of this parasite.

Oh my aching gut: irritable bowel syndrome, Blastocystis, and asymptomatic infection

Blastocystis is a prevalent enteric protozoan that infects a variety of vertebrates. Infection with Blastocystis in humans has been associated with abdominal pain, diarrhea, constipation, fatigue, skin rash, and other symptoms. Researchers using different methods and examining different patient groups have reported asymptomatic infection, acute symptomatic infection, and chronic symptomatic infection. The variation in accounts has lead to disagreements concerning the role of Blastocystis in human disease, and the importance of treating it. A better understanding of the number of species of Blastocystis that can infect humans, along with realization of the limitations of the existing clinical laboratory diagnostic techniques may account for much of the disagreement. The possibility that disagreement was caused by the emergence of particular pathogenic variants of Blastocystis is discussed, along with the potential role of Blastocystis infection in irritable bowel syndrome (IBS). Findings are discussed concerning the role of protease-activated receptor-2 in enteric disease which may account for the presence of abdominal pain and diffuse symptoms in Blastocystis infection, even in the absence of fever and endoscopic findings. The availability of better diagnostic techniques and treatments for Blastocystis infection may be of value in understanding chronic gastrointestinal illness of unknown etiology.

New insights on classification, identification, and clinical relevance of Blastocystis spp

SUMMARY

Blastocystis is an unusual enteric protozoan parasite of humans and many animals. It has a worldwide distribution and is often the most commonly isolated organism in parasitological surveys. The parasite has been described since the early 1900s, but only in the last decade or so have there been significant advances in our understanding of Blastocystis biology. However, the pleomorphic nature of the parasite and the lack of standardization in techniques have led to confusion and, in some cases, misinterpretation of data. This has hindered laboratory diagnosis and efforts to understand its mode of reproduction, life cycle, prevalence, and pathogenesis. Accumulating epidemiological, in vivo, and in vitro data strongly suggest that Blastocystis is a pathogen. Many genotypes exist in nature, and recent observations indicate that humans are, in reality, hosts to numerous zoonotic genotypes. Such genetic diversity has led to a suggestion that previously conflicting observations on the pathogenesis of Blastocystis are due to pathogenic and nonpathogenic genotypes. Recent epidemiological, animal infection, and in vitro host-Blastocystis interaction studies suggest that this may indeed be the case. This review focuses on such recent advances and also provides updates on laboratory and clinical aspects of Blastocystis spp.

Detecting Blastocystis using parasitologic and DNA-based methods: a comparative study

Few studies have targeted the relative performance of diagnostic methods used for the detection of Blastocystis, a unicellular organism often present in fecal specimens from individuals with and without gastrointestinal symptoms. Aims of this study included a comparison of the formol ethyl acetate concentration technique (FECT), permanent trichrome staining of feces fixed in sodium acetate-acetic acid-formalin (SAF-PST), xenic in vitro culture (XIVC), and polymerase chain reaction (PCR) regarding Blastocystis screening of 107 samples from 93 patients with suspected enteroparasitic disease. Compared with PCR, the sensitivity/specificity of XIVC, SAF-PST, and FECT was 89%/100%, 82%/100%, and 50%/100%, respectively. False-negative results generated by the FECT and SAF-PST appeared to be associated with Blastocystis sp. subtype 3. A comparison of results obtained by dideoxy sequencing of positive PCR products amplified from DNA extracted directly from feces and DNA extracted from 5- and 28-day-old XIVC of 10 randomly chosen Blastocystis isolates showed no disparities, indicating that XIVC has very little or no impact on subtype distribution or variation within a given specimen. It is recommended that short-term XIVC be used for cost-effective screening of fresh fecal specimens for Blastocystis infection to generate valid prevalence estimates and to identify isolates for molecular characterization in studies aiming to illuminate the molecular epidemiology of Blastocystis.

Is this recently characterized gastrointestinal pathogen responsible for rising rates of inflammatory bowel disease (IBD) and IBD associated autism in Europe and the United States in the 1990s?

In 2006, a pathogenic variant of the common intestinal organism Blastocystis was discovered in patients who were experiencing chronic gastrointestinal symptoms. Most species of Blastocystis inhabit humans with no symptoms. The discovery of a pathogenic variant of Blastocystis is significant, because Blastocystis is related to Entamoeba, a similar organism with pathogenic variants that kill over 100,000 people each year. Recent research has shown that Blastocystis infections may be undetectable using existing clinical methods. Medical case reports from the Middle East, Europe, and United States suggest that infection with this variant may already be widespread and misdiagnosed as one of several functional disorders.

HYPOTHESIS

A more virulent or transmissible type of Blastocystis emerged in the Middle East in the 1980's, and was transmitted to Europe and the United States by military and more significantly vacation and business travel. The lack of adequate tests made it impossible to detect the infection. Transmission to the larger population resulted in rising inflammatory bowel disease (IBD) rates in Europe in the 1990's. The relationship between IBD and autism is explored, along with the possibility that the same pathogen causes both conditions.

SUPPORTING DATA

Serological and epidemiological findings are presented supporting the hypothesis. Blastocystis survives sewage treatment, shows low host specificity, and can be spread by many animals. Several communities which have been studied due to high autism rates are located close to rivers which receive large quantities of sewage effluent, such as South Thames (England), Olmsted County (Minnesota, USA) and many communities in Oregon (USA).

CONCLUSIONS

Scientists from other countries represent the first line of defense against emerging infectious diseases, but their publications on Blastocystis are not well known in the United States and Europe. With the publication of corroborating research by Western scientists in core scientific journals, it is hoped that an appropriate response from the public health system will be forthcoming. Investigation into the existence of infection in the groups mentioned with sensitive and specific tests should be performed. Such tests could include a serum antibody test and a Polymerase Chain Reaction test specific to the pathogenic variant.

Colony growth of Philippine isolates of Blastocystis hominis in simplified, soft agar medium

The agar-cloning technique of Blastocystis hominis has been observed in both solid and semisolid agar using Iscove's modified Dulbecco's medium. In this study, Philippine isolates of B. hominis were grown by pour-plate method in semisolid agar using Locke's solution. Inoculated plates contained 0.7% agar, 10% horse serum, and 0.1% sodium thioglycollate. Plates were incubated at 37 degrees C in a microaerophilic jar for 7-10 days. Biconvex disk-shaped colonies were seen abound at the bottom half of the medium. Colonies growing at the agar-glass interface were flat and consisted of thin layers of cells. From these colonies, large amoeboid cells were frequently seen on the periphery, whereas smaller cells were concentrated at the core. Analysis of the SSU rDNA genetically established the identity of the clones to be B. hominis. This is the first report on agar cloning of Blastocystis in a compound medium.

Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which abdominal pain is associated with a defect or a change in bowel habits. Gut inflammation is one of the proposed mechanisms of pathogenesis. Recent studies have described a possible role for protozoan parasites, such as Blastocystis hominis and Dientamoeba fragilis, in the etiology of IBS. Dientamoeba fragilis is known to cause IBS-like symptoms and has a propensity to cause chronic infections but its diagnosis relies on microscopy of stained smears, which many laboratories do not perform, thereby leading to the misdiagnosis of dientamoebiasis as IBS. The role of B. hominis as an etiological agent of IBS is inconclusive, due to contradictory reports and the controversial nature of B. hominis as a human pathogen. Although Entamoeba histolytica infections occur predominately in developing regions of the world, clinical diagnosis of amebiasis is often difficult because symptoms of patients with IBS may closely mimic those patients with non-dysenteric amoebic colitis. Clinical manifestations of Giardia intestinalis infection also vary from asymptomatic carriage to acute and chronic diarrhoea with abdominal pain. These IBS-like symptoms can be continuous, intermittent, sporadic or recurrent, sometimes lasting years without correct diagnosis. It is essential that all patients with IBS undergo routine parasitological investigations in order to rule out the presence of protozoan parasites as the causative agents of the clinical signs.