[The distribution of intestinal parasites among children in Denizli]

Intestinal parasitic disease appears to be an important national health problem in our country. Parasitic infection distribution is related to the socioeconomic status and environmental factors. The aim of this study was to determine the distribution of intestinal parasites among children in the 1-15 age group in the Denizli province. Parasitic infection was observed in 256 (10.2%) out of 2518 children. The highest rate of 31.4% was that of Giardia intestinalis. The rates of Enterobius vermicularis and Blastocystis hominis were found to be 29.6% and 14% respectively.

[The role of protozoan parasites in etiology of urticaria]

In order to investigate a possible link between parasites and chronic urticaria, the prevalence of intestinal protozoans in stool samples of individuals with chronic urticaria (n=55) and healthy controls (n=43) were evaluated with native lugol, formol-ethyl acetate concentration and trichrom dye, modified acid fast. In the case of Giardia intestinalis (G. intestinalis) ELISA was also used. In the study 29.1% of the patients were found to have protozoan (Blastocystis hominis + G.intestinalis) infections. On the other hand, only 11.6% of the patients in healthy group were having a protozoon infection, all of which were B. hominis. There was no statistically significant difference between the patient group and control group regarding the frequency of B. hominis presence. Also, the number of G.intestinalis positive patients were also statistically different in patient group from those of healthy controls. In patients whom were positive for protozoan infections, agent specific therapy was used. In 7 of these patients symptoms of the disease were subsided with this therapy while six continued to have relapses. Three patients had missed the control visits therefore the course of the disease was not evaluated. As a conclusion, protozoans should be considered in the etiology of chronic urticaria and stool examination should be done in these patients routinely.

Association of Blastocystis subtype 3 and 1 with patients from an Oregon community presenting with chronic gastrointestinal illness

Chronic gastrointestinal illness of unknown etiology is a significant problem in the United States. Using a real-time LightCycler PCR assay we detected Blastocystis in nine patients from a metropolitan area of Corvallis, Oregon who presented with diarrhea, abdominal pain, fatigue, joint pain, skin rash and psychiatric co-morbidity. Phylogenetic analysis identified six infections with Blastocystis sp. subtype 3, and one with subtype 1, using the standard Stensvold nomenclature. Most patients with subtype 3 had previously tested negative with conventional parasitological diagnostics, had been symptomatic for over 4 years, and reported antibiotic failure.

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.

Drinking water: a possible source of Blastocystis spp. subtype 1 infection in schoolchildren of a rural community in central Thailand

In January 2005, a survey of intestinal parasitic infections was performed in a primary school, central Thailand. Of 675 stool samples, Blastocystis was identified with a prevalence of 18.9%. Genetic characterization of Blastocystis showed subtype 1 (77.9%) and subtype 2 (22.1%). Study of the water supply in this school was performed to find the possible sources of Blastocystis. Blastocystis from one water sample was identified as subtype 1, which had a nucleotide sequence of small subunit (SSU) ribosomal RNA (rRNA) gene that was 100% identical to that of Blastocystis infected in schoolchildren. Our information supports the evidence of water-borne transmission in this population.

Protein profile and morphometry of cultured human Blastocystis hominis from children with gastroenteritis and healthy ones

A total of 180 children of age group 5-12 years old in both sexes, of whom 90 were symptomatic and negative for other parasites, rotavirus or pathogenic bacteria. Another 90 children were asymptomatic, but with B. hominis in stools. Direct smear, formaline-ethyl acetate sedimentation concentration, kinyon carbol-fuchin stain, stool culture, enzyme immunoassay, culturing, morphometric study, gel electrophoresis and experimental infection of mice were done. The results showed that the central body cysts (CB), granular and multivacuolar forms isolated from symptomatic patients were larger than those from asymptomatic ones. The CB form was common compared to other forms and isolated from 104 cases. B. hominis infection was prevalent among males rather than females (60.5% versus 39.5%). The clinical data showed that diarrhea was the most common symptom (58.9%). The infection intensity had a direct relation with illness duration. The polyacrylamide gel electrophoresis showed that isolates from symptomatic and asymptomatic patients ranged between 24-130 kDa. All isolates showed similar banding patterns. Only minor differences was in low MW (30, 50 kDa) and in high MW (118 kDa) in samples from symptomatic patients. The histopathological examination of caecum, colon and small intestine of B. hominis mice infected from symptommatic patients showed infiltration with inflammatory cells and tissue invasion by the parasite.

Clinical significance of Blastocystis hominis: experience from a medical center in northern Taiwan

BACKGROUND AND PURPOSE

Blastocystis hominis is an intestinal protozoan. The pathogenic role of this organism in human beings is still controversial and has varied among reports from different geographic areas. The purpose of this study was to determine the clinical significance of B. hominis in northern Taiwan.

METHODS

A total of 100 patients who had a positive B. hominis stool examination during the period April to December of 2001 were retrospectively identified from Taipei Veterans General Hospital. The demographic and clinical characteristics of these patients were reviewed from the medical records.

RESULTS

All of the patients were adults. Fifty nine patients had more than one underlying diseases, including malignancies. Twenty one patients presented with fever and 10 patients had gastrointestinal symptoms, including diarrhea and/or abdominal pain. However, all of the patients had other conditions that might have contributed to the clinical presentation, and they improved without specific treatment for B. hominis. Furthermore, there were no significant differences in clinical symptoms and white blood cell count between patients with malignancy or diabetes mellitus and those without. Six patients had hypereosinophilia that could not be attributed to other causes. Among 34 patients who had a further stool examination within one year, B. hominis was undetectable in 31 patients (91.2%), despite their having no specific antiprotozoal treatment.

CONCLUSIONS

The association of clinical symptoms and B. hominis could not be delineated from our study, even in immunocompromised patients. All of the patients improved without receiving any specific therapy. More studies from different areas are needed in order to delineate the clinical significance B. hominis.

[The prevalence of Microsporidium among patients given a diagnosis of cancer]

The aim of this study was to determine the frequency of Microsporidium among patients given a diagnosis of cancer. For this purpose fecal samples from 320 patients aged 23.60+/-23.00 years were examined using native-Lugol and sedimentation methods and evaluated with modified trichrome, trichrome, and calcofluor dyes. Moreover a control group of 320 non-cancer patients was set up. While 10.9% of the patient group was found to have Microsporidium, only 5.6% of the control group did. Comparison between the control and patient groups in terms of presence of Microsporidium revealed a statistically significant difference. The analysis of a possible relation between intestinal parasites and the presence of Microsporidium revealed a statistically significant correlation between Microsporidium and Blastocystis hominis (P < 0.05). The frequencies of intestinal parasites in the control group and the patient group were found to be 17.8% and 18.1%, respectively. From the findings it was concluded that presence of intestinal parasites and Microsporidium in cancer patients can cause critical problems and adversely affect the therapy. Moreover it was suggested that cancer patients should be informed about regular feces examination and protection against parasites in order to improve their life standards and protect them against parasite infections during treatment.

[The distribution of intestinal parasites and their causative factors in children]

Intestinal parasitic infection prevalence in children who had been brought to our hospital together with related factors. The study was carried out in 400 children who were chosen at random among those brought to our hospital. All stool samples were examined with nativelugol, formol-ether, Kinyon acid-fast, methods. The cellophane tape preparations and hemoglobin concentration measurement were used. Intestinal parasites found in 156 of 400 (39%) children were Giardia intestinalis (19.8%) Enterobius vermicularis (15%), Blastocystis hominis (5.8%). Socio-economic and educational level of patient's family, living in urban area, having abdominal pain, anal itching, salivation during sleep, and nasal itching had been found related with the prevalence of parasitic infection. No relationship were found in the other factors. Because WHO guidelines favor routine screening and treatment of parasitic infections of school-age children when the prevalence of parasitic infections in community exceeds 50%, all children should be evaluated for parasitic infections if they have one or more risk factors.

Cross-sectional surveys and subtype classification of human Blastocystis isolates from four epidemiological settings in China

The prevalence and geographical distribution of the intestinal protozoa Blastocystis in humans across China is unknown, and the relative importance of different subtypes has yet to be investigated. We assessed the community prevalence and relative frequencies of different Blastocystis subtypes in four epidemiological settings in China, i.e., Shanghai municipality, Yongjia county (Zhejiang province), Eryuan county, and Menghai county (both Yunnan province). Blastocystis infection was detected with the culture method, and the subtype was identified with polymerase chain reaction using a set of subtype-specific primers. The prevalence at the four study settings was 1.9, 5.9, 18.4, and 32.6%, respectively. People aged greater than or equal to 60 years had a higher prevalence in the former two settings, Shanghai and Yongjia, whereas the highest infection rate was found among individuals aged 10-17 years in the latter two settings, Eryuan and Menghai. A higher prevalence was found in men in the former two settings but in women in the latter two settings. Five different Blastocystis subtypes were identified from the 192 isolates. Subtype 3 was the predominant type, followed by subtype 1. In conclusion, the epidemiology of Blastocystis varies across China.

Prevalence of Blastocystis hominis and Strongyloides stercoralis infection in Okinawa, Japan

This study was conducted to clarify the prevalence of Blastocystis hominis and Strongyloides stercoralis infection in Ryukyu University Hospital, Okinawa, Japan, between January 2004 and November 2006. Stool samples collected from 3,292 patients were examined by the direct smear method, formalin-ether sedimentation method, and agar plate culture method. The prevalence rate of B. hominis and S. stercoralis infection was 1.0 and 3.4%, respectively. The prevalence rate of B. hominis infection in patients aged >80 years old was significantly higher than that in patients <80 years old (P < 0.001). The prevalence rate of S. stercoralis infection was significantly higher in patients with B. hominis infection compared with those without (P < 0.001). This study demonstrated a prevalence rate for B. hominis and S. stercoralis infection and an association between B. hominis and S. stercoralis infection in Okinawa, Japan.

[Infection by Blastocystis: a review]

Blastocystis sp. is an anaerobic unicellular micro-organism belonging to the kingdom Chromista, frequently found in the digestive tracts of humans and animals, the pathogenic role of which continues being controversial for human beings. Its genetic classification, which shows nine sub-types, some of which seem to have a role in cases with gastrointestinal symptomathology, opens a new field for research. In this article, an extensive revision is carried out which includes the historic development of the parasite, its taxonomy, epidemiology, morphology, vital cycle, as well as biochemical, cytochemical and genetic aspects, the pathogenic role in contrast with different variables which include the sub-types, quantity, response to the treatment and association with other pathogens. Finally, the clinical and therapeutic aspects are also reviewed.

Molecular epidemiology of human Blastocystis in a village in Yunnan province, China

The purpose of this study was to improve our understanding of the molecular epidemiology of human Blastocystis, focusing on 239 randomly selected individuals in a single village in Yunnan province, China. Emphasis was placed on the relative frequency of different Blastocystis subtypes and underlying risk factors. We used a cross-sectional study design, by employing a pre-tested questionnaire to obtain demographic data and behavioural risk factors, and collected faecal samples for culture and subsequent identification of Blastocystis. DNA was extracted from Blastocystis isolates and the subtypes were identified using 7 subtype-specific sequenced-tagged site (STS) primers. Overall, 78 faecal samples were Blastocystis culture-positive (32.6%, 95% confidence interval: 26.7-38.6%). The majority (n=73, 93.6%) were single infections with one of the known subtypes, whereas 2 isolates consisted of 2 concurrent subtypes. The remaining 3 isolates could not be identified with the currently known STS primers. Risk factors for a Blastocystis infection were drinking unboiled water, consumption of raw water plants and pig ownership. The consumption of raw water plants was positively associated with subtype 1 infections, and drinking unboiled water with subtype 3 infections. In conclusion, human Blastocystis was common in this village in southwest China, and different subtypes were associated with distinct transmission routes or sources of infection, and hence Blastocystis subtypes might be linked to specific environmental compartments.

Prevalence of intestinal parasites among primary schoolchildren in Derna District, Libya

The prevalence of intestinal parasites and some hygienic factors was evaluated in primary schoolchildren in Derna District. A total of 1039 stool specimens were examined by direct smear and formaline-ether concentration methods. The results showed that 31% of the children were infected with at least one or two parasites. These parasites were Giardia lamblia (12.7%), Blastocystis hominis (6.7%), Entamoeba histolytica/ Entamoeba dispar (6.6%), Entamoeba coli (3.2%), E. hartmanni (1.0%), Enterobius vermicularis (0.6%), Ascaris lumbricoides (0.1%) and Hymenolepis nana (0.1%). A significant difference was between infection rate and parent's education (P = 0.000), socio-economic status of the family (P = 0.000), family size and number of rooms in houses (P = 0.000). Also, there was a significant differences between infection rate and source of water for human consumption (P = 0.05).

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.

Characteristics of Blastocystis hominis infection in a Turkish university hospital

In order to determine characteristics of Blastocystis (B.) hominis infection; 770 individuals' stool specimens were examined both by simple and concentration techniques and stained with iodine solution and trichrome in the Parasitology Laboratory of Hacettepe University Faculty of Medicine, Turkey. Among the examined 770 specimens, B. hominis was detected in 94 (12.2%). B. hominis was the most common intestinal parasite among the study group. It was mostly detected with Dientamoeba fragilis. Among the groups the incidence of B. hominis in allergic patients was higher than controls. Among the immunosuppressed patients, B. hominis was detected significantly higher in patients who had solid tumours. Of the 48 individuals who had only B. hominis in their stool the most common symptom was abdominal pain. Concentration technique with trichrome stain was more sensitive than simple smear with lugol solution for the detection of B. hominis. Studies with more patients must be planed to understand the B. hominis infection in solid tumour patients and coexistence of B. hominis and D. fragilis.

[Evaluation of intestinal parasites in a period of four years in the coprology laboratory of a training hospital]

Parasitological examination of stool samples of 9867 individuals, submitted from both inpatient and outpatient departments to the Microbiology Department of an 800-bed Training Hospital between 1.1.2003 and 31.12.2006, revealed that 582 individuals (5.9%) were infected with intestinal parasites. Different diagnostic methods were employed in two different periods, and Blastocystis hominis, Giardia intestinalis and Entamoeba histolytica/dispar were found to be the most common parasites, respectively. Patients were predominantly male (67% (n=336) male vs. 33% (n=165) female) and aged between 15-25 years (36%). In addition, 14% (81/582) patients had multiple parasitoses. Despite being labor-intensive, parasitological examination of stool samples with necessary staining methods by experienced staff will surely help determine both the diagnosis and exact prevalence of intestinal parasitic infections in Turkey.

[Is Blastocystis hominis an opportunist agent?]

Despite its high prevalence throughout the world, major issues about Blastocystis hominis remain unresolved, including fundamental areas such as taxonomy and pathogenicity. Sequences of the SSUrRNA gene place Blastocystis in the stramenophiles. Analysis of the elongation factor 1-alpha gene, however, indicates similarity to Entamoeba histolytica. There is considerable morphological variability and karyotype diversity, and it appears that more than one species is present in humans and animals. In culture, three major forms predominate: vacuolar, granular, and ameboid. The vacuolated form (usually 10 to 30 mum) was most frequently detected in fecal specimens. The prevalence of Blastocystosis in humans appears to be higher in developing countries (30% to 50%) than in developed countries (1.5% to 10%), and has been associated with travel. B. hominis is the most common parasite isolated from stool specimens in symptomatic and asymptomatic persons in a variety of settings. Isolates resembling B. hominis have been described in a variety of mammals, birds, reptiles, and even insects. The significance of this human infection is uncertain.

Frequency of Giardia lamblia among children in Dohuk, northern Iraq

Out of 1261 stool specimens collected from children in Dohuk city, northern Iraq, the prevalence of Giardia lamblia infection was 38.5%. The highest rate of infection was in orphan care centres (48.1%) and the lowest in the paediatric hospital (31.3%). The age group 10-12 years had the highest rate (81.2%) and 7-9 years the lowest (22.9%); boys had a higher rate than girls. Some infected samples (70/486) showed double or triple infections and G. lamblia was combined with Hymenolepis nana, Blastocystis hominis, Entamoeba histolytica and Iodamoeba buetschlii.

[Blastocystosis or Zierdt-Garavelli disease: a clinical pathway]

The author presents the clinical pathway of blastocystosis, a disease due to Blastocystis hominis, an intestinal parasite that has long been enigmatic, which can occasionally be the cause of clinical manifestations.

Infection of Blastocystis hominis in primary schoolchildren from Nakhon Pathom province, Thailand

A study was conducted to evaluate the infection status of Blastocystis hominis in children from four public schools in Phuttamonthon district, Nakhon Pathom province, Thailand during November to December 2004. A total of 814 faecal specimens were used for B. hominis cultivation using Jones' medium. Mixed infections with other intestinal parasites were also examined by formalin ethyl acetate concentration method. It was found that 13.51% (110 of 814) of the children examined were infected with B. hominis. Mixed infections with other intestinal protozoa and helminths were observed in 10.91% (12 of 110) of B. hominis positive specimens. There were Giardia lamblia cysts (4.55%), Trichomonas hominis trophozoites (1.82%), Entamoeba histolytica cysts (0.91%), Endolimax nana cysts (0.91%), Strongyloides stercoralis larvae (0.91%), hookworm eggs (0.91%), and Trichuris trichiura eggs (0.91%). Of the children positive for B. hominis, there was no significant differences between sex (P > 0.05) and showed no correlation between age and the percentage of infection. The different infection rates among four schools indicated the involvement of hygienic factors which promoted the infection of this common intestinal protozoan. Variation in size of B. hominis was found in culture medium, which might indicate to the presence of different strains of B. hominis infection.

Zoonotic protozoa--food for thought

Outbreaks of water- and foodborne diseases caused by Cryptosporidium, Giardia and Toxoplasma are well documented. Three features of these zoonotic protozoa ensure a high level of environmental contamination and enhance the likelihood of waterborne transmission. Firstly, they are responsible for disease in a broad range of hosts including man, have a low infectious dose enhancing the possibility of zoonotic transmission, secondly, their transmissive stages are small in size and environmentally robust and thirdly are insensitive to the disinfectants commonly used in the water industry. In addition, there is growing evidence for the role that water and food can play in the transmission of the microsporidia, Balantidium and Blastocystis to humans.

Epidemiology of Blastocystis hominis and other intestinal parasites in a Vietnamese female immigrant population in southern Taiwan

There has been a rapid increase in cross-border female marriage immigrants in Taiwan. In this study, 1,434 Vietnamese female marriage immigrants arriving between July 1998 and June 2001 were examined for intestinal parasites. Most (77.9%) of these women were 20-29 years of age. The prevalence of intestinal parasite infection was 37.7%, and the trend increased from 1999 to 2001 (statistically significant, p < 0.0001), but decreased among age subgroups (p < 0.0001). Among the 20 species of intestinal parasites found in this study, 10 species (27.8%) were transmitted via the fecal-oral route, 5 (14.6%) via the soil-mediated route, and 5 (0.7%) by food-borne infection. The prevalence of blastocystosis (20.4%) and hookworm (9.7%) remained high among this population. The results provide unprecedented information on intestinal parasitic infection among these immigrants in southern Taiwan and recommend that appropriate health care be given after parasite infection is confirmed in these migrant communities.

[Investigation of intestinal parasites in residents of the Kayseri Karpuzsekisi basin]

In this study, we collected stool and cellophane tape samples from residents in four villages located in the Kayseri-Karpuzsekisi basin in order to investigate the distribution of intestinal parasites. A total of 240 samples collected from Hanyeri (40), Sariküklü (20), Dokuzpinar (80) and Karpuzsekisi (120) were investigated. The parasites detected were as follows: Blastocystis hominis, 82 (34.16%); Enterobius vermicularis, 37 (15.41%); Entamoeba coli 26, (10.83%); Entamoeba hartmanni, 10 (4.16%); Giardia intestinalis, 7 (2.91%); Endolimax nana, 5 (2.08%); Entamoeba histolytica/E. dispar, 4 (1.66%); and Taenia saginata, 1 (0.41%).

Blastocystis hominis and other intestinal parasites in a community of Pitanga City, Paraná State, Brazil

The objective was to estimate the prevalence of Blastocystis hominis, to evaluate the effectiveness of different techniques for its diagnosis as well as to estimate the prevalence of other intestinal parasites in the community of Campo Verde, a district of Pitanga. The work was carried out from August to October 2004. Samples of feces from children and adults were collected and submitted to the techniques of direct wet mount, flotation in zinc sulphate solution, tube sedimentation, sedimentation in formalin-ether and staining by Kinyoun and iron hematoxylin methods. From 181 studied individuals, 128 (70.7%) showed protozoa and/or helminths in stool samples. The most prevalent species were Endolimax nana (33.7%); B. hominis (26.5%); Giardia lamblia (18.2%); Entamoeba coli (17.1%); Ascaris lumbricoides (16.6%); Iodamoeba bütschlii (9.4%); and ancylostomatidae (7.7%). B. hominis was only identified by the techniques of direct wet mount, sedimentation in formalin-ether and staining by iron hematoxylin, though the latter was less sensitive than the other methods. The high frequency of B. hominis demonstrated by this study indicates the need to include laboratory techniques that enable identification of the parasite on a routine basis.

Prevalence of Blastocystis hominis among "healthy" food handlers in Dammam, Saudi Arabia

A prospective study was carried out to see the prevalence of B. hominis in food handlers in Dammam, Eastern Province of Saudi Arabia. A total of 17073 food handlers were examined, 8.50% persons were positive for this organism in their stool. In 2.4% of the food handlers, B. hominis was the only parasite, whereas in 1.9% and 4.2% of the cases, this organism was found in association with pathogenic and non pathogenic parasites respectively. We could find the correlation between the dietary habits and the presence of organism in stool. In 19.9% of the positive food handlers in whom rice was the predominant food the organism was seen, when compared to 80.1% of the predominantly wheat eaters.

Elevada prevalência de blastocistose em pacientes do Centro de Saúde de Soledad, Estado Anzoátegui, Venezuela

Entre 98 exames parasitológicos de fezes de pacientes do Centro de Saúde de Soledad, Anzoátegui, Venezuela, foram encontrados 46 (46,9%) positivos para Blastocystis hominis.

Blastocystis hominis among symptomatic and asymptomatic individuals in Talkha Center, Dakahlia Governorate, Egypt

Blastocystis hominis is now getting acceptance as an agent of human intestinal disease. B. hominis in stool samples of symptomatic and asymptomatic individuals was evaluated as a possible cause of gastro-intestinal troubles. B. hominis was found in 106 (10.1%) out of 1050 individuals examined from six villages and one city in Talkha Center, Dakahlia Governorate. The highest infection rate was in Manshayt El-Badawy village (25.47%), whereas Talkha City showed the lowest rate (4.73%). Age group 10-20 years had higher infection (13.3%). In twenty-three symptomatic patients, B. hominis represented the only causative parasitic agent. The most common symptoms were diarrhoea (30.4%), abdominal pain (26.1%), flatulence (21.7%). vomiting (13.1%) and fatigue (8.7%). High concentrations of B. hominis were found in symptomatic patients than in asymptomatic ones with statistical significant difference (8.2 cells/100 x field versus 3.8 respectively). The mean number of B. hominis was significantly high in patients complaining of diarrhoea and abdominal pain.

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.

Prevalence of Blastocystis hominis infection in asymptomatic individuals from Bangkok, Thailand

Fresh stool examination was performed from 2,230 participants who enrolled in annual check-up programs of the Faculty of Medical Technology, Mahidol University in 1999-2000 and 2004. In this study, Blastocystis hominis infection was diagnosed by culturing in Jones' media. A total of 21% of fecal specimens (in 1999-2000) and 13.7% (in 2004) were positive for B. hominis. The vacuolated form was the predominant form found in culture solution after 48 hours of incubation. The distribution of infection was highest between the ages of 21-30 years (p<0.05). There was no significant difference in infection between male and female groups. Other parasites, eg Giardia lamblia, Entamoeba histolytica, Entamoeba coli, Endolimax nana, Trichomonas hominis, Strongyloides stercoralis, Opisthorchis viverrini and Taenia species, were also found by fresh stool examination.

[Epidemiologic and laboratory assessments of etiologic implications of Blastocystis hominis in gastrointestinal diseases]

Authors present the first laboratory and epidemiological results which reveal the circulation in a population of protozoan Blastocystis hominis and its implication in the determinations of some gastrointestinal troubles, with fever, diarrhea and constipation, intense intestinal meteorism, associated with abdominal pain and cramps. Out of the 3106 investigated patients, 9.7% presented B. hominis as a unique etiologic agent, with an increased prevalence in adults (74.3%) and women (65.3%). Blastocystis infection with clinical manifestations or its asymptomatic form is included among emergent diseases.

Epidemiological survey of Giardia spp. and Blastocystis hominis in an Argentinian rural community

The aim of this study was to relate personal data, socio-cultural and environmental characteristics, and the presence of symptoms/signs with the frequencies of Giardia spp. and Blastocystis hominis among a rural population in Buenos Aires Province, Argentina. Of the surveyed population (350), 3.7% were infected with only Giardia spp. or 22.9% with B. hominis, and 2.3% were infected with both protozoa. The frequency of infection according to sex; 6.1% of males were infected and 1.6% of females by Giardia spp., 26.7% and 19.5% by B. hominis, and 2.4% and 2.2% by both parasites, respectively. Giardia spp. was detected in only three adults (over 14 years), but B. hominis was more frequent in adults than in children. The prevalences of these protozoa in this community are lower than those reported by other Argentinean studies, which is probably associated with the low density of the studied population (5.95 inhab/km2). Statistical analysis revealed that a male sex, flooding of the home, the use of a latrine, and an abdominal pain were correlated with the presence of these parasites, which indicate the importance of these factors in rural communities.

Blastocystis hominis infection in irritable bowel syndrome patients

Irritable bowel syndrome (IBS) is a functional bowel disorder in which abdominal pain is associated with a defect or a change in bowel habits. Subtle inflammation, especially after infectious enteritis, has been sometimes suspected as one mechanism of pathogenesis. This research was performed (1) to evaluate the prevalence of parasitic infections and (2) the possible association of IBS and parasitic infections. Fifty-nine IBS patients were recruited using symptom-based criteria (Rome Criteria II) with an absence of intestinal parasitic infection by direct smear method. Stool samples of individual patients were examined using 7 methods, ie examination for stool occult blood, simple saline smear method, formalin-ether technique, culture for Blastocystis hominis, modified trichrome stain, modified Ziehl-Neelsen method, and trichrome stain for parasitic and bacterial infections. Of the 59 patients, stool samples of 13 patients (22.1%) were positive for parasites. These were B. hominis (13.6%), Strongyloides stercoralis larvae (1.7%), Giardia lamblia cysts (1.7%), and non-pathogenic protozoa, ie Endolimax nana cysts (5.1%). The prevalence rate of parasitic infections in the control group (20%) was not statistically different from the patients. There was no statistical difference between B. hominis infection in IBS patients and control was found in this study (p = 0.87). In the IBS group, B. hominis infection predominated (13.6%), while other parasitic infections were found in 8.5%. The culture method for B. hominis is more sensitive than the direct (simple) stool smear method, which is the routine diagnostic method in most laboratories. These results were also found in control group.

Elevada porcentagem de blastocistose em escolares de São Paulo, SP

Em exame parasitológico de fezes de 227 alunos de escola pública de São Paulo (SP), encontramos 87 (38,3%) positivas para Blastocystis hominis. A blastocistose ainda suscita controvérsias e indefinições, merecedoras de esclarecimentos sobretudo para evitar contratempos no âmbito da saúde pública e das atenções médico-assistenciais.

Evidence of waterborne transmission of Blastocystis hominis

A cross-sectional study was performed in February 2001 to evaluate the prevalence and risk factors of Blastocystis hominis infection in army personnel who resided in an army base in Chonburi, Thailand. A total of 904 army personnel were enrolled in this study. Short-term in vitro cultivation was used to detect B. hominis in stool samples. In this population, B. hominis was the parasite most frequently found, and was identified in 334 of 904 stool specimens (36.9%). A significant association between B. hominis infection and symptoms was identified that might emphasize the role of B. hominis as a human pathogen. After adjustment for potential confounders, significantly increased risk of being infection with B. hominis was associated with being a private, working in a specific unit, and consuming unboiled drinking water. Thus, waterborne transmission of B. hominis infection was indicated at this army base. However, other modes of transmission cannot be ruled out.

Comparison of methods for detecting Blastocystis hominis

In order to determine the comparative sensitivity of two methods of detecting Blastocystis hominis and to investigate the seasonality of infection with this enteric protozoan parasite, the present study was conducted. In each of two 3-month periods representing winter, spring (February-April) and summer (July-September), 500 routine stool submissions were examined for B. hominis using microscopy following either formol-ether concentration or in vitro culture using Jones' medium. The organism was detected in 39 of the 1,000 samples investigated using the in vitro culture technique and in none of the samples using the formol-ether concentration technique. In 82% of the B. hominis-positive samples, no concurrent bacterial or parasitic pathogens were found, and diarrhoea was the most commonly recorded symptom among patients. Infection was more prevalent in summer than in winter/spring, occurring primarily in the 71-80-year age group. Cysts were detected in 20.5% of positive samples, but only following Ficoll-Paque concentration of formol-ether concentrates. Cyst excretion was more prevalent in summer than in winter/spring.

[Prevalence of Blastocystis hominis among food handlers from Caroni municipality, Bolivar State, Venezuela]

A cross-sectional survey was conducted to determine the prevalence of Blastocystis hominis infection in a random sample of apparently healthy food handlers. A total of 415 individuals attending the Manoa Urban Outpatient Clinic (Caroní Municipality, Bolívar State, Venezuela) in the Adult Hygiene Program and who requested health certification to work as food handlers were studied. Stool samples obtained by spontaneous evacuation were examined by direct microscopy and the Willis concentration method. A total of 150 individuals were infected (36.14%), 107 (25.78%) of whom with B. hominis. There was no difference between males and females (p > 0.05), but there was a significant difference between ages (chi(2) = 12.17; g.l. = 4), with infection more frequent between 18 and 27 years. In 71.02% of the cases, B. hominis was the only parasite. Giardia lamblia was the parasite most frequently associated with B. hominis (2.41%). In the majority (85%) of infected individuals, less than five microorganisms per microscopic field were observed. We conclude that B. hominis is a frequent intestinal parasite among food handlers in Caroní Municipality, Bolivar State, Venezuela.

[Investigation of intestinal parasites in AIDS patients]

In this study, enteric parasites were investigated in the stool samples of 38 AIDS patients (23 with chronic diarrhea and 15 without diarrhea) prospectively. At least three stool samples from each patient were investigated microscopically for ova or trophozoites. The samples were concentrated with formol-ether method and wet preparations stained with lugol were examined. In addition, the concentrated samples were stained with modified asid-fast (Kinyoun's), rhodamine-auramine, modified trichrom and calcoflor methods. Enteric parasites were detected in 18 (47%) of the 38 patients, 16 patients harbored a single parasite, and 2 patients were found to be infected with more than one parasite. Only one (7%) of 15 AIDS patients without diarrhea, were found to be infected with Giardia lamblia. On the other hand, 17 (74%) of 23 AIDS patients with chronic diarrhea were found to be infected with various enteric parasites. Cryptosporidium spp. was detected in 9 (39%) of these 23 patients, and in 2 of them Microsporidium spp. accompanied Cryptosporidium. In 2 (9%) of these 23 patients G. lamblia were detected, while Isospora belli, Blastocystis hominis, Entamoeba histolytica, Strongyloides stercoralis and Trichuris trichiura were detected in one patient each. As a result, the detection rate of emerging parasites, including Cryptosporidium spp, Microsporidium spp, I. belli, B. hominis, and S. stercoralis was significantly higher than conventional parasites (39% versus 13%; z=2.34, p=0.01), and CD4 T cell counts were found to be significantly lower among AIDS patients with chronic diarrhea than those without diarrhea (x2=34.33, p<0.001).

Clinical characteristics and endoscopic findings associated with Blastocystis hominis in healthy adults

Ninety-nine individuals with stools positive for Blastocystis hominis but negative for other parasites were identified from medical records of healthy adults who had received a physical examination at Taipei Veterans General Hospital from November 2000 to October 2002. The medical records of these 99 positive cases and 193 randomly selected controls, matched for age, sex, and date of examination, were retrospectively reviewed. The pathogenicity of B. hominis could not be demonstrated due to a lack of association with the development of gastrointestinal symptoms or pathologic findings on endoscopic examination. Multivariate analyses revealed that chronic hepatitis B infection was a predisposing condition to the acquisition of B. hominis (odd ratio = 2.848, 95% confidence interval = 1.299-6.242, P = 0.009), and concentration of urate was significantly lower in B. hominis-positive individuals (mean +/- SD = 361.64 +/- 87.44 versus 392.57 +/- 93.38 micromol/L; P = 0.009). Among the 64 individuals who underwent gastric biopsy, Helicobacter pylori was found more frequently in the individuals harboring B. hominis (19 of 26 versus 15 of 38; P = 0.017).

Hematological effects of Blastocystis hominis infection in male foreign workers in Taiwan

Blastocystis hominis found in stool specimens has been the most frequently identified parasite among foreign workers from Southeast Asia in Taiwan since 1992. The prevalence of B. hominis was 14.1% in this study. In their quarantine physical examinations, 121 male Thai workers were examined hematologically and screened for stool parasites using the merthiolate-iodine-formaldehyde concentration method. Hematological values were compared in workers with and without a B. hominis infection. Multiple regressions were used to adjust for age. Those infected with any parasite other than B. hominis were excluded from further analysis. The workers infected with B. hominis had a lower leukocyte count (6.5+/-0.4 X 10(3)/microl) than those who were not (7.4+/-0.2 X 10(3)/microl). This was mainly caused by a reduced neutrophil count (3.2+/-0.4 vs 4.2+/-0.2 X 10(3)/microl). Hemoglobin (13.9+/-0.3 vs 14.5+/-0.1 g/dl) and hematocrit (41.4+/-0.6 vs 42.9+/-0.2%) were also reduced in B. hominis-positive workers.

Secretory and humoral antibody responses to Blastocystis hominis in symptomatic and asymptomatic human infections

The study included 3 groups of individuals, in the first 2 groups they had positive stool microscopic examinations only for B. hominis indicating blastocystosis, with and without gastrointestinal symptoms, respectively, while the last group included apparently healthy individuals with no parasites in stool. Stool and serum samples of these individuals were subjected to detection of anti-B. hominis fecal and serum IgA and serum IgG antibodies by indirect ELISA, and detection of B. hominis fecal and serum antigens by double sandwich ELISA. In symptomatic B. hominis infections with positive stool microscopy the study recorded first: specific secretory IgA and humoral IgA and IgG antibody responses at a prevalence of 100%, 83.3% and 86.6%, respectively, with an increased significant difference (P<0.001) of each from healthy controls, together with an increase in level of secretory IgA than that of humoral IgA antibody (P<0.001), and second: the presence of specific antigens in stool and serum at a prevalence of 96.6% and 90%, respectively. With an increased significant difference (P<0.001) of each from healthy controls together with the former at a higher level than the latter (P<0.05). In asymptomatic B. hominis infections with positive stool microscopy the study recorded first; absence of each of the studied specific secretory and humoral antibody responses with no significant difference (P>0.05) of each from healthy controls, and second; absence of specific antigens in stool and serum with no significant difference (P>0.05) of each from healthy controls nor from each other. The explanations and implications of these results are discussed.

A placebo-controlled treatment trial of Blastocystis hominis infection with metronidazole

Blastocystis hominis, previously considered a harmless yeast, is now classified as a protozoan inhabiting the human intestinal tract. The pathogenicity of B. hominis remains controversial and is currently the subject of extensive debate.1- 5 As a result of the uncertainty surrounding the pathogenic role of B. hominis, large-scale treatment trials of B. hominis infection have so far been lacking. In spite of this, several drugs have been reported to be active against the parasite.6-8 The present study was carried out in order to evaluate the efficacy of metronidazole treatment in inducing clinical remission and parasitologic eradication in immunocompetent individuals with B. hominis as the only evident cause of diarrhea.

Blastocystis hominis among food vendors in Xochimilco markets

Blastocystis hominis is a pathogenic protozoon that lives in the human bowel and causes diarrhea: the mode of transmission is a passive one, through the ingestion of stool-contaminated water or foods that contain infective forms of the parasite. The purpose of this study is to report the prevalence of Blastocystis hominis among food vendors in the markets within the Xochimilco jurisdiction, Mexico City, Mexico. A cross-sectional study was conducted in which food vendors answered an epidemiological questionnaire and underwent a serial stool culture. The frequency of the intestinal parasitoses reported was estimated and an analysis was carried out associating the presence of Blastocystis hominis with socio-economic and hygienic factors using the odds ratio at a 95% confidence interval. The frequency of intestinal parasites and commensals was 50.4%; Blastocystis hominis was found in 48 (41.7%) food vendors. The risk analysis showed that Blastocystis hominis was associated with: male gender, poor personal hygiene habits, personal history of parasitosis, and family history of parasitosis. The prevalence reported is high when compared with other populations studied. The relevance of this report lies on the fact that food vendors handle foods and could transmit the infection to consumers.

[Human blastocystosis: prospective study symptomatology and associated epidemiological factors]

An attempt has been made to contribute to the understanding of the symptoms and factors associated with the Blastocystis Hominis infection, as seen in persons seeking outside consultation from the Dermatological and Transmissible Diseases Department (DTDD) at the C.H.N.H. This is a case-control study carried out in people between the ages of 5 and 80 in a period from January to March 1999. The cases tested positive in parasitological tests for Blastocystis Hominis and were absent of other enteropathogens. The controls tested negative in parasitological tests for Blastocystis Hominis and were absent of other enteropatoghens. A clinical chart was used to register details of symptomatology and factors associated with the Blastocystis Hominis infection. 74 cases and 70 controls were studied, matched by sex and age. A statistical correlation was obtained (p<0.05) among symptomatic persons and presence of Blastocystis Hominis (91,9%). The symptomatology associated with the Blastocystis Hominis infection by order of statistical significance (p<0.05) was: Abdominal pain (OR=3) 1.47<OR<6.60, abdominal ballooning (OR=2.36) 1.06<OR<5.29, urticaria (OR=3.19) 0.81<OR<12.48. The only risk factor associated with the Blastocystis Hominis infection was the consumption of unboiled water (OR=2.52) 1.01<OR<5.83. In conclusion, Blastocystis Hominis is associated to symptomatic subjects with abdominal pain and ballooning and urticaria, who possess at least two or three positive tests. This infection would be facilitated by the consumption of unboiled water.

Incidence of Blastocystis hominis in faecal samples submitted for routine microbiological analysis

Over a one-year period, 1390 faecal samples were submitted to Aberystwyth Public Health Laboratory for routine microbiological examination. All were stained using a commercial trichrome method. Blastocystis hominis was detected in 96 (6.9%), making it the most common parasite found in the study. Of the B. hominis-positive specimens, 73% were missed on direct microscopy. Molecular typing of B. hominis has revealed extensive genetic diversity in morphologically identical strains and thus detection by microscopy alone may not be sufficient to confirm the role of this organism in human disease.