Zoonotic genotypes of Blastocystis hominis detected in cattle and pigs by PCR with diagnostic primers and restriction fragment length polymorphism analysis of the small subunit ribosomal RNA gene

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.

Molecular prevalence of Blastocystis sp. and subtype diversity in fecal samples collected from cattle in dairy farms in Turkey

Close contact with infected animals is one of the main risk factors for zoonotic transmission of enteric protozoan parasite Blastocystis and thus, several animal species are being screened for the detection of the zoonotic subtypes. For this purpose, 22 fecal samples were collected from healthy cattle aged > 2 months and 39 fecal samples were also collected from cattle (aged <2 months) which are treated with TMP-SMX due to diarrhea. Later, Blastocystis sp. and subtypes were investigated by a PCR targeting the SSU rRNA gene and subsequently by sequencing. Among the 22 fecal samples collected from healthy cattle, Blastocystis was detected in 12 of them with a prevalence rate of 54.5 %. Among Blastocystis-positive samples, five different subtypes (ST3, ST5, ST10, ST12, and ST13) were detected. The predominant subtype was ST10 (allele 152) with a prevalence rate of 50 % (6/12). In the other group treated with TMP-SMX due to diarrhea, Blastocystis was detected in only one (2.56 %;1/39) fecal sample and its subtype was ST1 (allele 2). High prevalence of Blastocystis as well as predominance of ST10 (allele 152) were detected in healthy cattle. The identification of zoonotic ST1, ST3, ST5 and ST12 subtypes among the detected subtypes with a high prevalence (46.1 %; 6/13) showed the importance of cattle as a source for transmission of Blastocystis to humans. It was observed that the efficiency of TMP-SMX on the clearance of Blastocystis in cattle was very strong. Moreover, to our knowledge, this is the first study detecting Blastocystis ST13 subtype in the cattle.

Global prevalence, subtypes distribution, zoonotic potential, and associated risk factors of Blastocystis sp. in domestic pigs (Sus domesticus) and wild boars (Sus scrofa): A systematic review and meta-analysis

The intestinal parasite Blastocystis sp. is a widely distributed protist among humans and various animal hosts, with significant prevalence in developing countries. Due to the zoonotic nature of its subtypes (STs), we aimed at global estimation of the prevalence, STs distribution, zoonotic potential, and associated risk factors of Blastocystis sp. infection in domestic pigs (Sus domesticus) and wild pigs/wild boars (Sus scrofa). The study was designed and conducted in 2021 via searching articles in PubMed, Scopus, Google Scholar, and Web of Science databases, based on the PRISMA checklist, and meta-analysis was done using a random-effects model to calculate the weighted estimates and 95% confidence intervals (95% CIs). Totally, 43 papers (47 datasets) reported data on 7977 examined pigs in 24 countries with a total prevalence of 50.9% (95% CI: 42.8-59%). In details, prevalence was higher among domestic pigs [52.4% (95% CI: 43.9-60.7%)] than wild boars [31.2% (95% CI: 11.2-62%)], but is poorly statistically supported as far as the CIs largely overlap. Out of 28 reported STs, nine (ST1-ST7, ST10, and ST15) were reported from domestic pigs, while six (ST1, ST3-ST5, ST8, and ST15) had been isolated from wild boars. Among nine zoonotic STs (ST1-ST8, and ST12), all were identified in examined swine populations, except for ST12. As well, ST1 and ST5 were probably the most frequently circulating STs among these animals. In addition, male and older pigs showed higher Blastocystis sp. infection. Altogether, Blastocystis epidemiology and the distribution of its related STs in pigs is still open to question and requires more extensive studies, especially in the neglected regions of the world.

Detection and molecular identification of Blastocystis isolates from humans and cattle in northern Egypt

Blastocystis is one of the less well-understood waterborne protozoa of medical and veterinary importance. The present study aimed to detect, identify, and subtype Blastocystis in cattle and humans in northern Egypt and to investigate the potential for zoonotic transmission. Fecal samples were collected from 136 humans (68 in contact with animals and 68 no animal contact) and 190 cattle from a rural area in Kafr El-Sheikh Province, Egypt. All samples were microscopically examined by direct wet mount technique and cultured in Jones' medium. Genomic DNA was extracted from positive cultures. A region of the Blastocystis small subunit ribosomal ribonucleic acid (SSU rRNA) gene was amplified using PCR. Blastocystis subtypes were identified by sequencing of the amplified SSU rRNA gene. The relatedness of sequence types obtained in this study and others submitted in GenBank was compared according to their genetic relatedness. Out of 136 human and 190 cattle samples, Blastocystis was detected in 53 (38.9%) and 37 (19.4%), respectively using either culture or direct wet mount. Blastocystis SSU rRNA gene was amplified in 55 samples (32 humans and 23 animals). Six subtypes were identified (STs 1-3 in humans and ST4, ST10 and ST14 in cattle) and were distinguishable with inter (up to 0.075) and intra (up to 0.024) subtype variations. A close phylogenetic relationship between human and animal isolated STs 1-4 was demonstrated. To the best of our knowledge, this is the first study to investigate the the potentiality for zoonotic transmission of certain Blastocystis subtypes in northern Egypt.

A systematic review and meta-analysis on the global prevalence and subtypes distribution of Blastocystis sp. infection in cattle: A zoonotic concern

Blastocystosis is an interesting parasitosis, since the parasitic infection is still seriously neglected and a considerable zoonotic evidence is emerging. Blastocystis sp. infects the intestinal lumen of humans and a wide range of animals, while there is a lack of comprehensive information on Blastocystis epidemiology in cattle worldwide. Thus, the present systematic review and meta-analysis were performed by exploring four electronic databases (PubMed, Web of Science, Scopus, and Google scholar) for relevant published papers up to 7th November 2020, utilizing a random-effects model to pool estimations and assign 95 % confidence intervals (CIs). Results of 28 studies (29 datasets) on cattle showed a 24.4 % (95 % CI: 16.9-33.9 %) prevalence for Blastocystis infection. Also, 16 out of 26 reported subtypes (STs) were isolated from cattle, with ST10 (18 datasets) as the highest-reported [32.3 % (95 % CI: 21.6-45.3)] as well as ST24 and ST25 (one study each) as the lowest-reported STs [1.4 % (95 % CI: 0.2-9.1)]. Additionally, among nine well-known zoonotic STs (ST1-ST8 and ST12), all STs except for ST8 were reported from cattle worldwide, demonstrating this animal species as a potential reservoir for human infections. Meanwhile, the overall prevalence of Blastocystis in various subgroups (publication year, WHO regions, countries, continents, and age groups) was analyzed separately. The finding of the present review article highlights the cattle as a significant source of zoonotic transmission of Blastocystis infection to humans, which must be considered for preventive measures.

Molecular detection and subtype distribution of Blastocystis in farmed pigs in southern China

Blastocystis is one of the most common causative agents of intestinal diseases, which can cause enteric diseases in animals and humans. However, limited data is available on the prevalence or subtypes of Blastocystis infections in farmed pigs in southern China. In this study, a total of 396 fecal samples were collected from farmed pigs in three provinces in southern China in 2016, and screened for Blastocystis by PCR amplification of the small subunit rRNA (SSU rRNA) gene fragment. One hundred and seventy (42.93%) of the examined fecal samples were detected Blastocystis-positive, and two known zoonotic subtypes ST1 and ST5 were identified, with ST5 being the predominate subtype. Moreover, gender, age and region were considered as risk factors that associated with Blastocystis infection in farmed pigs. The present study revealed the prevalence and subtypes of Blastocystis infections in farmed pigs in southern China, which provided essential data for the control of Blastocystis infections in pigs, other animals and humans in China.

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 report on the prevalence and subtype distribution of Blastocystis sp. in dairy cattle in Lebanon and assessment of zoonotic transmission

Blastocystis sp. is frequently identified in a wide range of animal hosts, including bovids. Because of its burden and zoonotic potential, this parasite has been sought in domestic cattle from various countries, since this livestock may also represent a possible reservoir of human infection. However, epidemiological data regarding the prevalence and ST distribution of Blastocystis sp. in this animal group is lacking in Lebanon. Therefore, faecal samples were collected from a total of 254 dairy cattle raised on 55 farms located in the North Lebanon region and screened for the presence of the parasite by quantitative real-time PCR. The overall prevalence of Blastocystis sp. was shown to reach 63.4% in cattle livestock. Sequence analysis of positive samples indicated the presence of seven STs, with predominance of ST10 (44.0%) and ST14 (36.8%) and lower proportions of ST2 (8.0%), ST1 (7.2%), ST5 (2.4%), ST3 and ST7 (0.8% each). This survey was the first conducted worldwide reporting ST2 and ST7 in domestic cattle and confirmed that ST10 and ST14 represent cattle-adapted STs in view of their high prevalence. Faecal samples from in-contact dairy farmers and patients hospitalised in the same Lebanese governorate who reported no contact with cattle livestock were also analysed for the presence of Blastocystis sp. The same three STs were identified in both human cohorts, with predominance of ST3, followed either by ST1 or ST2 depending of the group. No other STs, including ST10 or ST14, have been reported. Moreover, even though ST1, ST2 and ST3 were found to be common to dairy cattle and farmers cohorts, only one ST3 isolate showed 100% sequence identity between both hosts. Consequently, the presence and low prevalence of ST1, ST2, ST3, ST5 and ST7 identified herein in domestic cattle, most of which exhibit low host specificity, could be derived from occasional direct exposure to faecal material from human and non-human hosts or by ingestion of contaminated drinking water or food in the enclosure of the farms. Together with the absence of ST10 and ST14 in the human population, these data suggest that cattle play a negligible role as zoonotic reservoirs of Blastocystis sp.

A Simple Genotyping Method for Rapid Differentiation of Blastocystis Subtypes and Subtype Distribution of Blastocystis spp. in Thailand

Blastocystis spp. is one of the most common protozoa of humans and animals worldwide. The genetic diversity of Blastocystis spp. might be associated with a wide range of symptoms. However, the prevalence of each subtype is different in each country. Until now, there is no standard method for subtyping of Blastocystis spp. We developed a sequential restriction fragment length polymorphism (RFLP) analysis for the rapid differentiation of human Blastocystis subtypes. A large-scale study was also conducted to determine the subtype distribution of Blastocystis spp. in Thailand. Stool samples were collected from 1025 school-age students in four regions of Thailand. Blastocystis infections were identified by direct smear, formalin ethyl-acetate concentration technique (FECT), Boeck and Drbohlav’s Locke-Egg-Serum (LES) medium culture, and polymerase chain reaction (PCR) of small-subunit ribosomal DNA (SSU rDNA). Subtypes of Blastocystis spp. were determined by RFLP. Phylogenetic tree of partial SSU rDNA sequences of Blastocystis spp. was constructed using the Maximum Likelihood (ML) method. Out of 1025 students, 416 (40.6%) were positive for Blastocystis spp. Using two steps of RFLP reactions, we could determine subtype one–three among these students. Subtype 3 was the most common subtype (58.72%) in Thai students, followed by subtype 1 (31.2%), and subtype 2 (10.1%). Blastocystis subtype 3 was the most prevalent in all regions of Thailand. The subtype distribution of Blastocystis spp. in Thailand was different from other countries.

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.

Association of Helicobacter pylori and protozoal parasites in patients with chronic diarrhoea

Introduction An association of Helicobacter pylori and common protozoal parasites in patients with abdominal discomfort and chronic diarrhoea is unclear and may be pathological. Materials and methods One hundred and sixty-one patients with diarrhoea were compared to 114 age and sex matched controls. Stool samples were examined by microscopy and DNA extracted for PCR with specific primers for H. pylori and protozoal parasites Blastocystis sp., Entamoeba sp. (Entamoeba histolytica, Entamoeba dispar and Entamoeba moshkovskii) and Giardia duodenalis (G. duodenalis). Results There was a marked difference in the presence of parasites between patients and controls: no parasite 42/75%, one parasite 42/15%, two or more parasites 16/10%, respectively (p < 0.001). Patients with diarrhoea were more likely to be infected with Blastocystis sp (p < 0.001), E. histolytica (p = 0.027) and E moshkovskii (p = 0.003). There was no difference in the frequency of H. pylori (p = 0.528), G duodenalis (p = 0.697) or E dispar (p = 0.425). Thirty-three patients and 27 controls had H. pylori infection. Of these, 22 patients and 6 controls were infected with Blastocystis sp (p = 0.001), 6 patients and no controls were infected with E. histolytica (p = 0.02), whilst 7 patents and 9 controls were infected with E dispar (p = 0.292). Conclusion In this population, diarrhoea is linked to infection with Blastocystis sp, E. histolytica and E moshkoviskii. In H. pylori infection, diarrhoea is linked to Blastocystis sp and E. histolytica infection. These associations may be linked pathogenically.

Molecular characterization of Blastocystis from pigs in Shaanxi province of China

Blastocystis is an enteric eukaryote of mystery for its ubiquitous presence in animals and humans worldwide and a broad diversity genetically. The animals have been suggested to be an important reservoir to transmit Blastocystis to humans because of high colonization frequency and the presence of zoonotic subtypes. In the present study, the prevalence and subtypes of Blastocystis in pigs in Shaanxi province of China were determined using the molecular technique based on the small subunit rRNA (SSU rRNA) gene fragment. Of 560 pig faecal samples collected from different geographical origins, 419 (74.8%) were positive for Blastocystis colonization. The prevalence was significant affected by the age and the geographical origin. Four subtypes, including three zoonotic (ST1, ST3 and ST5) and one animal specific (ST10) subtypes, were identified. To our knowledge, this study provides the first run-through information for colonization of Blastocystis in pigs in China.

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.

Advantage of using colonic washouts for Blastocystis detection in colorectal cancer patients

Background

There have been previous studies associating microorganisms to cancer and with our recent findings of Blastocytsis antigen having a higher in vitro proliferation of cancer cells strengthens the suspicion. Collecting faecal samples alone to associate this parasite with cancer may not be accurate due to the phenomenon of irregular shedding and the possible treatment administrated to the cancer patients. Hence, this become the basis to search for an alternate method of sample collection. Colonic washout is an almost complete washed up material from colon and rectum which includes various microorganisms such as Blastocystis and other lodged material within the villi. The detection of parasite in colonic washouts will give a better reflection on the association between Blastocystis and CRC.

Methods

Blastocytsis detection was made by in vitro culture method using Jones’ medium, formal ether concentration technique and conventional polymerase chain reaction (PCR) on faecal samples and colonic washouts of 204 CRC patients from colonoscopy procedure. Faecal samples and colonic washouts from 221 normal individuals served as control.

Results

We observed an increased detection of Blastocystis using colonic washouts (n = 53, 12.47%) than faecal samples (n = 26, 6.12%). Eleven faecal samples showed positive results for Blastocystis which were also found in colonic washouts using the PCR technique. This study for the first time showed a significant Blastocystis infection among CRC patients (n = 43, 21.08%) compared to the asymptomatic normal individuals (n = 22, 9.95%). Blastocystis subtype 3 infection was found to be significantly more prevalent (n = 26, 12.75%) compared to other subtypes namely subtype 1: n = 9 (4.41%), subtype 2: n = 1 (0.49%), subtype 5: n = 1 (0.49%) and mixed subtype: n = 6 (2.94%) among the CRC patients.

Conclusion

The study showed that colonic washouts provide a better alternative for Blastocystis detection in CRC patients compared to faecal samples as this prevents treatment regime and the phenomenon of irregular shedding from influencing the detection results obtained from faecal samples.

Cytokine changes in colonic mucosa associated with Blastocystis spp. subtypes 1 and 3 in diarrhoea-predominant irritable bowel syndrome

We determined cytokines (e.g. interleukin-8, 10, 12 and TNF-α) expression by peripheral blood mononuclear cells (PBMCs) and in rectal mucosa in diarrhoea-predominant irritable bowel syndrome (D-IBS) with Blastocystis spp. Eighty patients with D-IBS and Blastocystis spp. infection were classified as 'cases' and 80 with D-IBS without Blastocystis spp. infection were classified as 'control'. Cases were subdivided into D-IBS and Blastocystis sp. defined type 1 (subtype-specific primer SB83) and type 3 (SB227). Stool microscopy and culture were performed. Rectal biopsies were obtained for histology and cytokines by real-time PCR for mRNA expression of cytokines. PBMCs IL-8 was similar in different groups but in type 1, IL-8mRNA was increased compared with type 3 (P = 0·001) and control (P = 0·001). In type 1, IL-10 by PBMCs had a low mean value (14·5±1·6) compared with (16·7±1·5) type 3 and (16±2·3) in controls (P<0·001 and P<0·001, respectively). In Blastocystis sp. type 1, low IL-10 was associated with lymphocyte and plasma cell infiltration (P = 0·015 and P = 0·002, respectively). In Blastocystis sp. type 1 and type 3, IL-12 was associated with goblet cell depletion 23 (85%) (P<0·001) and 8 (29%) (P = 0·037), respectively. In Blastocystis sp. type 1, low IL-10 was associated with a proinflammatory response characterized by IL-8.

Genetic diversity of blastocystis in livestock and zoo animals

Blastocystis is a common unicellular anaerobic eukaryote that inhabits the large intestine of many animals worldwide, including humans. The finding of Blastocystis in faeces in mammals and birds has led to proposals of zoonotic potential and that these hosts may be the source of many human infections. Blastocystis is, however, a genetically diverse complex of many distinct organisms (termed subtypes; STs), and sampling to date has been limited, both geographically and in the range of hosts studied. In order to expand our understanding of host specificity of Blastocystis STs, 557 samples were examined from various non-primate animal hosts and from a variety of different countries in Africa, Asia and Europe. STs were identified using 'barcoding' of the small subunit rRNA gene using DNA extracted either from culture or directly from faeces. The host and geographic range of several STs has thereby been greatly expanded and the evidence suggests that livestock is not a major contributor to human infection. Two new STs were detected among the barcode sequences obtained; for these, and for three others where the data were incomplete, the corresponding genes were fully sequenced and phylogenetic analysis was undertaken.

Subtype distribution of Blastocystis isolates from a variety of animals from New South Wales, Australia

A total of 438 stool samples from 38 different species of animal from seven different locations were studied for the presence of Blastocystis. PCR analysis was completed on all samples and DNA sequence data from the rDNA were submitted to subtype allocation. There was a total of 80 (18%) sequences from 18 species, and nine different subtypes were identified - ST1, ST2, ST3, ST4, ST5, ST7, ST11, ST12 and ST13. This is the first report of Blastocystis from the eastern grey kangaroo, red kangaroo, wallaroo, snow leopard and ostrich. This study highlights the need for further investigation into the genetic diversity of Blastocystis which could help show the zoonotic potential of Blastocystis.

Identification of Blastocystis subtype 1 variants in the Home for Girls, Bangkok, Thailand

A cross-sectional study of Blastocystis infection was conducted to evaluate the prevalence, risk factors, and subtypes of Blastocystis at the Home for Girls, Bangkok, Thailand in November 2008. Of 370 stool samples, 118 (31.9%) were infected with Blastocystis. Genotypic characterization of Blastocystis was performed by polymerase chain reaction and sequence analysis of the partial small subunit ribosomal RNA (SSU rRNA) gene. Subtype 1 was the most predominant (94.8%), followed by subtype 6 (3.5%) and subtype 2 (1.7%). Sequence analyses revealed nucleotide polymorphisms for Blastocystis subtype 1, which were described as subtype 1/variant 1, subtype 1/variant 2. Blastocystis subtype 1/variant 1 was the most predominant infection occurring in almost every house. The results showed that subtype analysis of Blastocystis was useful for molecular epidemiological study.

Subtype distribution of Blastocystis isolates identified in a Sydney population and pathogenic potential of Blastocystis

Blastocystis is one of the most common enteric parasites present in humans. There is still much uncertainty about the pathogenic potential of this parasite, and it was suggested that its pathogenicity could be subtype-related. This report aimed to study 98 Blastocystis isolates found in human stool specimens to identify the subtypes present and carry out phylogenetic analysis on these isolates. This study also aimed to show the relationship between subtype and symptoms. Five-hundred and thirteen stool samples were submitted to five different diagnostic techniques for the detection of Blastocystis. Polymerase chain reaction (PCR)-positive samples were then sequenced and the small subunit (SSU) rDNA sequences were aligned and submitted to phylogenetic analysis. Ninety-eight samples were positive by any of the diagnostic methods for Blastocystis and 96 were positive by PCR. There were seven different subtypes (1, 2, 3, 4, 6, 7 and 8) identified by PCR and sequencing. This is the first large-scale study to examine the occurrence of Blastocystis in Australia. This study reports the high incidence of subtype 3 (44 %) in this population and discusses the emerging idea of subtype-dependent pathogenicity.

Detection of concurrent infection of dairy cattle with Blastocystis, Cryptosporidium, Giardia, and Enterocytozoon by molecular and microscopic methods

Of fecal specimens examined from 47 dairy cattle ranging in age from neonates to multiparous cows, 9, 10, 24, and 17 were positive for Blastocystis spp., Cryptosporidium spp., Giardia duodenalis, and Enterocytozoon bieneusi, respectively, as determined by PCR. Eight 3- to 5-month-old cattle were concurrently infected with three or four of these parasites. This is the first report to identify multiple concurrent infections with these four potentially zoonotic protist pathogens in cattle. None of the cattle exhibited signs of illness or effects of infection on growth and are regarded as healthy carriers. A commercially available immunofluorescence (IFA) microscopic test confirmed six of seven available PCR-positive Blastocystis specimens and identified one IFA-positive cow that was PCR negative.

In vitro sensitivity of Blastocystis hominis to garlic, ginger, white cumin, and black pepper used in diet

To determine the growth pattern and in vitro susceptibility of Blastocystis hominis to metronidazole (MTZ), garlic, ginger, white cumin, and black pepper. Stool specimens were collected from 16 irritable bowel syndrome (IBS) and 10 controls between July-November 2010. Stool microscopy and culture for B. hominis was performed. Drug susceptibility assays was done using 0.01 and 0.1 mg/ml of MTZ, garlic, ginger, white cumin, and black pepper. Effect was assessed on B. hominis culture after 48 h. Stool DNA was extracted using stool DNA extraction kit (Qiagen) and polymerase chain reaction (PCR) done using subtype-specific sequence-tagged-site primers. B. hominis genotype 3 and coinfection of 1 and 3 tended to grow well in culture compared to isolated type 1 infection. Exposed to MTZ at a concentration of 0.01 mg/ml, 38% (6/16) B. hominis from IBS did not grow in culture compared to 100% (10/10) of B. hominis from control (p = 0.001). When they were exposed to MTZ at 0.1 mg/ml, 56% (9/16) B. hominis from IBS did not grow in cultures compared to 100% (10/10) from control (p = 0.01). Forty-four percent (7/16) B. hominis from IBS did not grow in culture compared to 100% (10/10) B. hominis from control when exposed to garlic at a concentration of 0.01 mg/ml (p = 0.003) and following exposure to garlic at 0.1 mg/ml, 38% (6/16) B. hominis from IBS did not grow in cultures compared to 100% (10/10) from control (p = 0.001). B. hominis isolates from IBS had a cell count of 6,625 at a MTZ concentration of 0.01 mg/ml that reduced to 1,250 as MTZ concentration was increased to 0.1 mg/ml (p = 0.08). B. hominis from IBS with a mean cell count of 3 × 10(5) at baseline decreased to 1 × 10(4) when exposed to garlic at 0.01 mg/ml (p < 0.001) and to 1 × 10(3) (p < 0.001) when garlic was 0.1 mg/ml. B. hominis from IBS cell count decreased to 1 × 10(5) when exposed to white cumin at 0.01 mg/ml (p = 0.01) and to 1 × 10(5) (p < 0.001) when white cumin was 0.1 mg/ml. Exposed to black pepper at 0.1 mg/ml, cell count of B. hominis from IBS decreased to 1 × 10(5) (p = 0.01). B. hominis from IBS decreased to 1.3 × 10(5) exposed to ginger at 0.01 mg/ml (p = 0.001). B. hominis isolates were mostly genotypes 3, type 1 and 3 coinfection, and non-typeable B. hominis isolates. B. hominis isolates from IBS mostly genotype 1 demonstrated an increased sensitivity to garlic at 0.01 mg/ml with a B. hominis cell count of 3,714 compared to 6,142 when exposed to 0.01 mg/ml of MTZ. However, this sensitivity did not increase as garlic concentration was increased to 0.1 mg/ml, for B. hominis cell count was 6,000 compared to 1,428 as MTZ was increased to 0.1 mg/ml.

Irritable bowel syndrome: is it associated with genotypes of Blastocystis hominis

Blastocystis hominis is the most common intestinal parasite in humans. An extensive genetic variability has been described recently in B. hominis isolates. The aim of this study was to analyze genotypes of B. hominis isolates obtained from the healthy individuals and patients with irritable bowel syndrome-diarrhea (IBS-D). The patients with IBS-D were enrolled from gastroenterology outpatient department at the Aga Khan University Hospital. History and physical examination was done. Stool microscopy, culture, and polymerase chain reaction for B. hominis genotyping were carried out. The study included 158 patients with IBS-D, mean age 41 +/- 15, age range 16-83 years, and male/female ratio of 109:49. One hundred fifty-seven (49.8%) were taken as healthy control. The dominant B. hominis genotypes were genotype 1 in 87 (65%) and type 3 in 49 (37%). In IBS-D, genotype 1 was present in 75 (86%; P < 0.001) compared to 12 (14%) in controls while type 3 was present in 23 (47%) compared to 26 (53%) in controls (P < 0.001), respectively. Infection with single genotype of B. hominis was present in 70 (73%) with IBS-D and in 26 (27%) in control group while with multiple genotypes in 25 (64%) in IBS-D and 14 (36%) in control group (P = 0.30), respectively. Majority of our patients had typeable B. hominis infection. The genotype of B. hominis in IBS-D was type 1 while in control genotype 3 was predominant.

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.

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.

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.

Subtype distribution of Blastocystis isolates from synanthropic and zoo animals and identification of a new subtype

Blastocystis isolates from 56 Danish synanthropic and zoo animals, 62 primates primarily from United Kingdom (UK) collections and 16 UK primate handlers were subtyped by PCR, sequencing and phylogenetic analysis. A new subtype (ST) from primates and artiodactyls was identified and designated as Blastocystis sp. ST10. STs isolated from non-human primates (n=70) included ST3 (33%), ST8 (21%), ST2 (16%), ST5 (13%), ST1 (10%), ST4 (4%) and ST10 (3%). A high prevalence of ST8 was seen among primate handlers (25%). This ST is normally very rare in humans, suggesting that acquisition of Blastocystis ST8 infections from primates by their handlers had occurred in these cases. Data from published studies of non-human primates, other mammals and birds were collected and interpreted to generate a comprehensive overview on the ST distribution in such animals. On the basis of information on 438 samples, it was found that Blastocystis from primates belong mainly to ST1, ST2, ST3, ST5 and ST8, ungulates and dogs mainly ST1, ST2, ST3, ST5 and ST10, rodents ST4 and birds mainly ST6 and ST7. The data indicate moderate host specificity, most clearly exemplified by the fact that STs isolated from avian and non-avian hosts rarely overlap.

Phylogenetic analysis of Blastocystis isolates from animal and human hosts in the Philippines

To study the genetic diversity and cross-transmissibility of Blastocystis species in naturally infected hosts, 12 Blastocystis isolates from animal and human hosts in the Philippines were analyzed by sequencing the full-length small subunit ribosomal RNA (SSU rRNA) genes. Each sequence showed very high similarity (from 97% to 100%) to homologous sequences of other Blastocystis isolates reported previously. Phylogenetic analysis revealed that the 12 isolates were classified into 4 genetically distinct subtypes: 1, 2, 3, and 6. Results showed that Blastocystis subtypes 1, 2, and 3 were shared by isolates from varied hosts. This study confirms the remarkable heterogeneity of SSU rRNA gene among different Blastocystis isolates. The findings of this study agree with previous reports that the different Blastocystis subtypes have low host-specificity, comprising isolates from humans and various animal hosts. This study also suggests evidence for zoonotic transmission of the parasite and cross-transmissibility among heterogeneous hosts.

A possible link between subtype 2 and asymptomatic infections of Blastocystis hominis

Blastocystis hominis is one of the most common eukaryotic organisms in the intestinal tract of humans, while its pathogenic potential is still controversial. A total of 286 stool samples obtained from adult and pediatric patients with or without gastrointestinal symptoms in two hospitals in Manisa, Turkey, were cultured to detect B. hominis infection. Forty-one and 51 isolates were obtained from the adults and children, respectively, and these isolates were subjected to subtyping by polymerase chain reaction (PCR) with the known sequence-tagged site primers. The correlation between the genotype and the symptoms was evaluated. PCR subtyping indicated that subtype 3 was the most common genotype in both symptomatic and asymptomatic groups, and the second common genotype was subtypes 1 and 2 in symptomatic and asymptomatic groups, respectively. A significant correlation between subtype 2 and the asymptomatic groups was found among both in pediatric and adult patients (chi(2) (cal) = 4.38, df = 1, p = 0.044). However, there were no significant differences between the other genotypes and the symptomatic or asymptomatic groups, as well as both the age and sex of the patients. The present study suggests that subtype 2 is a non-pathogenic genotype of B. hominis.

Predominance of subtype 3 among Blastocystis isolates from a major hospital in Singapore

Blastocystis is an enteric protozoan parasite commonly found in humans and animals. Phylogenetic and genotypic analyses have shown that Blastocystis exhibits extreme genetic diversity, and humans are host to a number of zoonotic isolates. In the present study, the prevalence of Blastocystis in 276 stool samples from a hospital in Singapore was examined, and for the first time, riboprinting using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the genetic diversity of the Blastocystis isolated from the Singapore population. The prevalence rate was determined to be 3.3% (9/276), and Blastocystis displaying two main ribotypes were isolated. As a comparison, we performed PCR-RFLP using two different published methodologies, and both methods allowed the isolates to be divided into two distinct groups based on their riboprint patterns. According to a recently proposed classification scheme, 78% (7/9) of the isolates were of subtype 3, while 22% (2/9) were subtype 1. The predominance of subtype 3 in an urbanized city state such as Singapore is in agreement with the idea that subtype 3 is a genotype of human origin.

Ultrastructural and phylogenetic studies on Blastocystis isolates from cockroaches

Four Blastocystis isolates from cockroaches were established and these isolates were morphologically confirmed as Blastocystis organisms by light and/or electron microscopy. As these isolates were morphologically indistinguishable from Blastocystis isolated from other animals, phylogenetic analyses were conducted using their small subunit ribosomal RNA genes. A analyses of these sequences with previously reported ones that had been classified into nine Blastocystis clades indicated the presence of a new clade that comprised only Blastocystis organisms from cockroaches (clade X). A clade comprised of amphibian and reptilian Blastocystis organisms (clade IX) was located at the basal position of the Blastocystis tree together with the common ancestor of Proteromonas and Protoopalina, clade X emerged after the divergences of these two basal clades and its branching position was clearly supported by bootstrap analysis.

Blastocystis sp. subtype 5: a possibly zoonotic genotype

Blastocystis has a widespread distribution in a variety of animals, which is a potential source of infection for humans. Previous studies show that Blastocystis sp. subtypes 1-4, 6, and 7 were composed of isolates from humans and animals, while Blastocystis sp. subtype 5 included only pig and cattle isolates. A more recent study on the basis of the SSU rDNA sequence has showed that a single Blastocystis isolate amplified directly from the faeces of a Thai human belongs to Blastocystis sp. subtype 5, but that study failed to cultivate this isolate. We report herein two human isolates from in vitro cultures belonging to Blastocystis sp. subtype 5 and one human isolate from in vitro culture containing two distinct genotypes of Blastocystis sp. subtypes 3 and 5 using PCR amplification with seven kinds of sequence-tagged site (STS) primers. Additionally, 16 Blastocystis isolates from pigs living in the same rural area with the three humans infected Blastocystis sp. subtype 5 were also genotyped by PCR with the STS primers, and all isolates from pigs and humans were compared by small-subunit ribosomal RNA (SSU rRNA) restriction-fragment-length polymorphism (RFLP) analyses using two restriction endonucleases (HinfI and RsaI). The results indicated that all of the isolates from pigs showed Blastocystis sp. subtype 5 and the RFLP patterns of all of the isolates from humans except for the mixed one were identical or quite similar to those of the 16 pig isolates with both HinfI and RsaI enzymes. These findings provide additional molecular-based evidence supporting the zoonotic potential of Blastocystis sp. subtype 5. This study also showed that Blastocystis sp. subtype 3 overgrew Blastocystis sp. subtype 5 in vitro.

Terminology for Blastocystis subtypes--a consensus

Blastocystis is a ubiquitous enteric protistan parasite that has extensive genetic diversity and infects humans and many other animals. Distinct molecular methodologies developed to detect variation and obtain information about transmission patterns and clinical importance have resulted in a confusing array of terminologies for the identification and designation of Blastocystis subtypes. In this article, we propose a standardization of Blastocystis terminology to improve communication and correlate research results. Based primarily on published small-subunit ribosomal RNA gene analyses, we propose that all mammalian and avian isolates should be designated Blastocystis sp. and assigned to one of nine subtypes.

Infectivity of different genotypes of human Blastocystis hominis isolates in chickens and rats

Most Blastocystis hominis isolates from humans are believed to be potentially zoonotic. This is because B. hominis isolates found in a variety of other host species have been found to have identical or relatively similar genotypes to those found in human isolates. However, the transmission of human B. hominis isolates to other animals has not been confirmed experimentally. In this study, the infectivity associated with several unique human Blastocystis genotypes (subtypes 2, 3, 4 and 7) was therefore investigated by infecting chickens and rats with two isolates of each subtype experimentally. The results showed that one isolate of subtype 4 and one isolate of subtype 7 was capable of infecting both chickens and rats, while two isolates of subtype 2, another isolate of subtype 4, and another isolate of subtype 7 could only infect chickens. Conversely, two isolates of subtype 3 failed to infect either of the animals. These results confirmed that several genotypes from human isolates could infect chickens and/or rats, indicating that chickens and rats are suitable experimental animal models for studying the zoonotic potential of human Blastocystis isolates.

Blastocystis: subtyping isolates using pyrosequencing technology

Blastocystis is a prevalent single-celled enteric parasite of unresolved clinical significance. Efforts based on molecular methodologies to establish whether pathogenicity is linked to specific isolates of the genetically diverse genus of Blastocystis have been scarce and so far yielded ambiguous results which can be difficult to interpret. To alleviate some of the problems related to unravelling the molecular epidemiology of Blastocystis infections we developed and evaluated a simple and high-throughput sequence analysis (SQA) pyrosequencing technique based on the detection of genotype-specific nucleotide polymorphisms in the 18S small subunit rRNA gene for a rapid and cost-effective post-PCR screening of Blastocystis genotypes. The method was effectively capable of genotyping 48/48 isolates positive by nested PCR in approximately one hour, and in 94% of the cases the isolate detected by PCR and pyrosequencing was also detected by one of two different PCR assays with subsequent dideoxy sequencing.

Direct characterization of Blastocystis from faeces by PCR and evidence of zoonotic potential

In vitro propagation followed by PCR, and a PCR-based method capable of the direct detection of Blastocystis in faeces were utilized to detect Blastocystis from various hosts in Australia, including primates and their handlers from the Perth Zoo. In addition, Blastocystis isolates from dogs and humans living in a localized endemic community in Thailand were also characterized genetically. PCR-based detection directly from faeces was shown to be more sensitive compared with in vitro culture for the detection of Blastocystis. Moreover, phylogenetic analysis of Blastocystis isolates amplified utilizing in vitro techniques prior to PCR revealed that this method favoured the preferential amplification of Blastocystis subtype 5 over subtype 1. This study is the first to provide molecular-based evidence supporting the zoonotic potential of Blastocystis in dogs, possums and primates in a natural setting.

DETECTION OF BLASTOCYSTIS HOMINIS IN UNPRESERVED STOOL SPECIMENS BY USING POLYMERASE CHAIN REACTION

Blastocystis hominis is a common enteric parasite of worldwide distribution. Its pathogenetic potential has not yet been established, although numerous case reports suggest that B. hominis may cause the development of various gastrointestinal symptoms and disorders. The detection of the parasite in stool specimens is conventionally done by microscopy of direct smears, fecal concentrates, or permanently stained smears; however, morphology-based diagnosis is problematic. The aim of this study was to develop and evaluate a polymerase chain reaction (PCR) technique for the direct detection of B. hominis in human stool samples. Primers were based on small subunit ribosomal DNA and able to detect > or =32 parasites/200 mg stool artificially spiked with cultured B. hominis. In the evaluation of 43 clinical specimens, the PCR was tested against the formol ethyl acetate concentration technique (FECT) and a culture technique, proving 100% test specificity and a significantly higher sensitivity than the FECT. The PCR method is recommended for screening clinical specimens for B. hominis infection and for use in prevalence studies.

Genetic variability of Blastocystis hominis isolates in China

To determine if genetic diversity of Blastocystis hominis exists in China, 35 B. hominis isolates obtained from 19 asymptomatic infected individuals and 16 patients with gastrointestinal symptoms were genotyped by PCR using seven pairs of known sequenced-tagged site (STS) primers. Out of the 35 isolates, 29 were identified as one of the known genotypes, while five isolates showed two distinct genotypes, and one isolate was an unknown genotype as this was negative with all the STS primers. In this study, none of the isolates was classified as subtypes 4-7. Compared with the spectrum of human B. hominis subtypes obtained from five geographically different countries (Japan, Pakistan, Bangladesh, Germany, and Thailand), these results showed that subtype 1 was more a popular genotype (18/35) in China. In addition, two groups of the isolates from 19 asymptomatic infected individuals and those from 16 patients with intestinal symptoms were compared with the PCR-based subtype classification. The results suggest a possible relationship between subtype 1 and a pathogenic potential of this parasite.

Analysis of the ITS region and partial ssu and lsu rRNA genes of Blastocystis and Proteromonas lacertae

Blastocystis is a common single-celled enteric parasite found in a large variety of hosts. Recent molecular analysis supports the concept that this eukaryotic organism is a stramenopile most closely related to Proteromonas lacertae, a parasite of reptiles. In this study, the internal transcribed spacer region, partial small subunit rRNA and large subunit rRNA genes from 7 Blastocystis isolates (5 human, 1 pig and 1 sheep), and a Proteromonas lacertae isolate were amplified by PCR, cloned and sequenced. Blastocystis was found to be a typical eukaryote with both ITS1 and ITS2 regions present. Phylogenetic analysis based on the entire PCR amplicon revealed that the Blastocystis isolates did not segregate according to host or geographic origin. The highest sequence identities with the conserved Blastocystis 5.8S rDNA sequence were with the stramenopiles Fibrocapsa japonica, Chattonella marina, Cylindrotheca closterium and Hyphochytrium catenoides. The most parsimonious tree based on the 5.8S rDNA sequence from P. lacertae, 11 other stramenopiles, 2 fungi, 3 algae and 3 alveolates showed Blastocystis positioned within the stramenopiles, with P. lacertae as its closest relative. This work therefore supports the hypothesis that Blastocystis is most closely related to P. lacertae, and that it should be regarded as an unusual stramenopile.

Molecular characterization of Blastocystis isolates in the Philippines by riboprinting

Extensive genomic polymorphism has been demonstrated among morphologically identical Blastocystis isolates. To this end, 32 Blastocystis isolates from the Philippines (12 from humans, 12 from pigs and 8 from chickens) were analyzed genetically by riboprinting or restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR) amplified small subunit rDNA. Three distinct riboprint patterns were observed from the HinfI digestion, while four patterns resulted from the RsaI digestion of Blastocystis SSU rDNA. Restriction fragment profiles between Blastocystis isolates from different hosts were generally different from each other. However, Blastocystis isolates within each host group were practically the same. Cluster analysis of the riboprint patterns revealed seven distinct groups of the Blastocystis isolates, including a zoonotic strain. These results demonstrate the genetic heterogeneity of Blastocystis in the Philippines and a support to the idea of the organism's zoonotic potential.

Infectivity of Blastocystis isolates from chickens, quails and geese in chickens

The infectivity of six Blastocystis isolates obtained from two domestic chickens, two Japanese quails and two domestic geese, were examined in 1-week-old male chicks. All six isolates were able to infect the chicks via the intracecal inoculation of 1x10(6) cells of cultured organisms. Since the infected chicks discharged many cysts in their feces, the infectivity of the concentrated cysts in chicks was compared among three isolates from different bird species. The CK86-1 and QQ93-3 isolates, which were obtained from a chicken and a quail, respectively, were successfully infected in chicks by orally inoculating with 1x10(2)-1x10(6) cysts. On the other hand, the AC03-1 isolate from a goose required more cysts to infect the chicks, from 1x10(3) cysts to 1x10(6) cysts. In addition, when an uninfected normal chick was housed with five experimentally inoculated chicks with cysts of the QQ93-3 isolate, the normal chick became infected, indicating the fecal-oral transmission of the cyst form among the birds. These results show that the transmission of Blastocystis infection occurs easily between the same or different bird species. Therefore, the proposal of new Blastocystis species on the basis of different avian host species is problematic.

Blastocystis in humans and animals: new insights using modern methodologies

Among the waterborne protozoan parasites of medical and veterinary importance, Blastocystis is perhaps one of the less well-understood. However, in recent years, there has been a surge of interest in the organism, fueled in part by the possible association of Blastocystis infection with intestinal disorders, and its unusual taxonomic affiliations. Although there is information on the parasite's morphology, taxonomy and mode of transmission, its pathogenicity, life cycle, and function of certain organelles continue to baffle investigators. The clinical relevance of Blastocystis will be better answered once an animal model is found. Blastocystis infections have a worldwide distribution but prevalence is highest in areas with poor hygiene and deficient sanitation services and facilities. Application of modern molecular tools has advanced knowledge of the organism's genetic diversity, taxonomy and zoonotic potential.

Molecular phylogenies of Blastocystis isolates from different hosts: implications for genetic diversity, identification of species, and zoonosis

Small-subunit (SSU) rRNA gene sequences were obtained by PCR from 12 Blastocystis isolates from humans, rats, and reptiles for which elongation factor 1alpha (EF-1alpha) gene sequences are already available. These new sequences were analyzed by the Bayesian method in a broad phylogeny including, for the first time, all Blastocystis sequences available in the databases. Phylogenetic trees identified seven well-resolved groups plus several discrete lineages that could represent newly defined clades. Comparative analysis of SSU rRNA- and EF-1alpha-based trees obtained by maximum-likelihood methods from a restricted sampling (13 isolates) revealed overall agreement between the two phylogenies. In spite of their morphological similarity, sequence divergence among Blastocystis isolates reflected considerable genetic diversity that could be correlated with the existence of potentially >/=12 different species within the genus. Based on this analysis and previous PCR-based genotype classification data, six of these major groups might consist of Blastocystis isolates from both humans and other animal hosts, confirming the low host specificity of Blastocystis. Our results also strongly suggest the existence of numerous zoonotic isolates with frequent animal-to-human and human-to-animal transmissions and of a large potential reservoir in animals for infections in humans.

Fecal-oral transmission of the cyst form of Blastocystis hominis in rats

The infectivity of two Blastocystis hominis strains, RN94-9 and NIH:1295:1, was examined in 3-week-old SPF Wistar rats. The NIH:1295:1 strain, originally isolated from a guinea pig, was only able to infect rats via intracecal inoculation of the cultured organisms, while the RN94-9 strain, originally isolated from a laboratory rat, was able to infect rats by oral inoculation of the cultures due to the presence of a cystic form in the in vitro culture. Since many cysts were discharged in the feces of the infected rats, the infectivity of the concentrated cysts was compared between the two strains. Successful oral infection was observed in rats inoculated with 1 x 10(2)-1 x 10(6) cysts of the RN94-9 and NIH:1295:1 strains. The infectivity of the ten cysts varied in the three experiments of ten rats, being 20-100% and 30-100% in the RN94-9 and NIH:1295:1 strains, respectively. When an uninfected normal rat was housed with five experimentally inoculated rats, the normal rat became infected, demonstrating the fecal-oral transmission of the cyst form of this parasite. These results show that the Wistar rat is an ideal host for the propagation of strains RN94-9 and NIH:1295:1 of B. hominis, and demonstrate that the cyst form is the only transmissible form of this parasite.