Association of Blastocystis hominis with signs and symptoms of human disease

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

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

Prevalence and Associated Factors of Blastocystis sp. Infection in Patients with Gastrointestinal Symptoms in Spain: A Case-Control Study

Blastocystis sp. is known to be the most prevalent parasite in fecal samples of humans worldwide. In the present report, a case–control study (1:9.89 (≈10)) was performed, by analyzing data from 3682 patients who attended a public hospital in the northern area of Spain showing gastrointestinal symptoms. Diagnosis was performed in human fecal samples by means of optical microscopy. The prevalence of Blastocystis sp. in patients with gastrointestinal symptoms was 9.18% (338/3682). Most of the Blastocystis sp.-infected patients tested negative for protozoa and helminths, and were underweight and foreign-born (26.4%), mainly from Africa and Central/South America. Gastrointestinal symptoms, such as abdominal pain, anorexia, halitosis, plus relative eosinophilia, as well as co-infections with pathogenic bacteria were associated with Blastocystis sp. infection. Both type 2 diabetes and treatment with immunosuppressive medicines at the time of Blastocystis sp. detection were associated with a higher proportion of infected patients. This is the first case–control study of Blastocystis sp. in humans in northern Spain and may contribute to surveillance and intervention strategies by public health authorities.

Relative Frequency of Blastocystis Subtypes 1, 2, and 3 in Urban and Periurban Human Populations of Arequipa, Peru

Blastocystis is one of the most common protozoa found in the human gut and are genetically diverse and widely distributed around the world. Nonspecific and inconsistent symptoms have been associated with this protozoon; thus, its clinical importance remains controversial. Our aim was to estimate the relative frequency of Blastocystis subtypes 1, 2, and 3, which are the predominant subtypes reported in South America, based on conserved regions of SSU rDNA sequences and determine the factors associated with them. A total of 116 Blastocystis-positive stool samples were processed using conventional PCR with Blastocystis-specific primers. We identified subtype 1 (10.3%), subtype 2 (7.8%), subtype 3 (25.0%), and mixed subtype infections (8.7%). However, we could not identify any Blastocystis subtypes in 48.3% of the samples; therefore, it is likely that other subtypes were present in the area. No association was found between any gastrointestinal symptom and single or mixed Blastocystis subtypes. We found a statistically significant association between Blastocystis subtype 2 and irritable bowel syndrome (OR = 17.8, 95% CI = 1.5-408.4, p = 0.039); however, the number of samples with IBS was small (n= 4). There was no association between the Blastocystis subtypes and any epidemiological variable studied. In rural populations, we only identified subtype 1, while in urban and periurban populations, we identified subtypes 1, 2, and 3.

Blastocystis hominis: A Pathogenic Parasite

Background: Blastocystis hominis is recognized as a common intestinal parasite. Some studies have reported the effect of phenotypic, serologic, and biochemical indices on the parasites’ pathogenic characteristics. Objectives: This study aimed to introduce B. hominis as a pathogen, trying to change views about this parasite and introduce it as a parasite important in medical sciences. Methods: An open-ended, language-restricted (English) search was conducted in MEDLINE (PubMed), CINAHL, Scopus, and the Cochrane Library databases (from 1990 to 2018) using specific search criteria to identify Blastocystis spp. Results: The search of the literature retrieved 158 published articles on Blastocystis spp. Among these articles, the ones related to the pathogenicity of B. hominis were selected for further investigations. Results obtained in this study showed that the number of articles within five-year periods had an increasing trend. Also, studies of B. hominis have mainly investigated its pathogenic characteristics, accounting for 37.34% of the studies. Conclusions: This study showed comprehensive reasons for proving the pathogenesis of the parasite. It is hoped that further studies would fill the existing gaps regarding this parasite and identify its true identity as a medically important parasite.

Antiprotozoal potential of Salvadora persica against three virulent subtypes of Blastocystis sp

Blastocystis sp. is a group of anaerobic protozoa parasitizing the gastrointestinal tract of humans and a broad variety of animals. Evidences of Blastocystis parasites resistance development to antiprotozoal drugs urge the exploration of new therapeutics. Antiprotozoal potential of Salvadora persica, a medicinal plant traditionally used for oral hygiene, was evaluated in vitro against Blastocystis sp. human isolates. Until now, no study has described the effect of S. persica extracts on this parasitic protozoa. Blastocystis sp. positive stool samples collected from patients with gastrointestinal complaints and asymptomatic individuals diagnosed by microscopy were furthermore cultured in vitro and characterized by PCR and multiplex-PCR using sequence-tagged-site primers to determine their subtypes. Out of 21 Blastocystis sp. isolates, five were determined as ST1, 14 as ST3, and two as ST5 subtypes. Antiprotozoal activity of untreated and heat-treated S. persica roots aqueous extracts was evaluated in vitro by serial dilutions on three Blastocystis sp. subtypes; ST1, ST3, and ST5 isolated from symptomatic patients. A significant killing activity was observed with both, untreated and heat-treated aqueous extracts of S. persica at minimal concentration of 2.5 μl/ml compared to parasites' growth controls (P < 0.05). Maximal antiprotozoal effect was reached at a concentration of 20 µl/ml of S. persica aqueous extract. Means of growth inhibition effect obtained with untreated and heat-treated extracts at 40 µl/ml against the three subtypes of Blastocystis sp. were 80% (SD 2.3) and 82% (SD 1.1), respectively. No significant difference was observed in the inhibitory effect of S. persica extracts between the three Blastocystis sp. subtypes. Aqueous extract of S. persica roots contains therefore heat-stable components with significant antiprotozoal activity against Blastocystis sp. subtypes ST1, ST3, and ST5 in vitro. Further investigations are required to determine and characterize the active antiprotozoal components of S. persica roots and their evaluation in vivo.

Sexual Transmission of Intestinal Parasites and Other Enteric Pathogens among Men Who Have Sex with Men Presenting Gastrointestinal Symptoms in an STI Unit in Barcelona, Spain: A Cross-Sectional Study

Sexually transmitted infections (STIs) are a major problem worldwide. In addition, the spectrum of STIs is now expanding, including parasitic, bacterial, and viral infections. The study retrospectively describes the presence of enteric pathogens among 73 patients with gastrointestinal symptoms of enteritis and proctocolitis attending to an STI unit in Barcelona, Spain, between 2015 and 2016. Only patients investigated for intestinal parasitic infections were included in the study. Different diagnostic procedures were established for the detection of parasites, bacterial enteropathogens, and other STI agents. Entamoeba histolytica was the most prevalent pathogen in our cohort (20.5%), especially among individuals with proctocolitis. Contrarily, Giardia intestinalis was detected in 11.0% of patients, only associated with enteritis cases. Polymicrobial infections were common in our study (45.2%). Of note, 55.6% of shigellosis cases were coinfected with E. histolytica. The investigation highlights the importance of including parasites as differential gastrointestinal diagnosis, disregarding travel history, particularly among risk populations.

Occurrence of Blastocystis-subtypes in patients from Italy revealed association of ST3 with a healthy gut microbiota

An epidemiological survey on Blastocystis was carried out enrolling a total of 2524 subjects referred to the Umberto I Academic Hospital in Rome, for the routine parasitological exams, during 2017–2018. The studied population included a sample of immunocompromised individuals (N = 130) followed at the same hospital.

DNA sequencing of the small subunit rRNA gene (SSU rDNA) locus was performed on samples positive to the coproparasitological analysis to molecular characterize the Blastocystis-subtypes.

Microscopical analysis detected Blastocystis in 192/2524 (7.6%) of the enrolled subjects. It was the organism most frequently identified in the analysed faecal samples diagnosed in single infection (5.6%) or in co-infection with other enteric protozoa (2%). Furthermore, it was found mainly in immunocompromised patients (22.3%) compared to immunocompetent ones (6.8%).

As expected, ST3 was the most occurring subtype identified in 40% of the subjects, followed by ST1 (29%), ST2 (16%), ST4 (12%), and ST7 (3%).

Next-generation sequencing (NGS) of the 16S rDNA was performed on a sub-sample of Blastocystis-ST3-carriers, homogenous by age and gender, as well as on Blastocystis-free subjects, to profile and compare their gut bacterial composition. A higher bacterial diversity was found in ST3-Blastocystis-carriers, which exhibited a high abundance of Prevotella, Methanobrevibacter and Ruminococcus while, a high percentage of Bacteroides was found in Blastocystis-free subjects.

This study evidenced the presence of Blastocystis in 7.6% of faecal samples in Italy and a high circulation of the protist among immunocompromised patients (22.3%). Molecular characterization of positive samples evidenced the occurrence of five different subtypes, including zoonotic ST such as the ST7, highlighting the risk of transmission from animals. Study of the gut microbiota composition confirms previous evidences according to which, the colonisation by Blastocystis would be linked with an eubiotic gut characterized by potentially beneficial species such as Prevotella and Ruminococcus, rather than with a dysbiotic state, with a high abundance of Enterobacteriaceae, and corroborated the role of the protist as “an old friend” of the human gut.

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Microscopical analysis detected Blastocystis in 7.6% subjects in Italy.

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Molecular methods allowed the identification of 5 STs (ST1, ST2, ST3, ST4, ST7).

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ST3 resulted the most frequent subtype.

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NGS of the 16S rDNA gene was performed in Blastocystis-ST3-carriers.

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Blastocystis-ST3 resulted correlated to an eubiotic gut characterized by potentially beneficial species.

Interactions between a pathogenic Blastocystis subtype and gut microbiota: in vitro and in vivo studies

BACKGROUND

Blastocystis is a common gut eukaryote detected in humans and animals. It has been associated with gastrointestinal disease in the past although recent metagenomic studies also suggest that it is a member of normal microbiota. This study investigates interactions between pathogenic human isolates belonging to Blastocystis subtype 7 (ST7) and bacterial representatives of the gut microbiota.

RESULTS

Generally, Blastocystis ST7 exerts a positive effect on the viability of representative gut bacteria except on Bifidobacterium longum. Gene expression analysis and flow cytometry indicate that the bacterium may be undergoing oxidative stress in the presence of Blastocystis. In vitro assays demonstrate that Blastocystis-induced host responses are able to decrease Bifidobacterium counts. Mice infected with Blastocystis also reveal a decrease in beneficial bacteria Bifidobacterium and Lactobacillus.

CONCLUSIONS

This study shows that particular isolates of Blastocystis ST7 cause changes in microbiota populations and potentially lead to an imbalance of the gut microbiota. This study suggests that certain isolates of Blastocystis exert their pathogenic effects through disruption of the gut microbiota and provides a counterpoint to the increasing reports indicating the commensal nature of this ubiquitous parasite.

Prevalence of non-pathogenic types of gastrointestinal protozoa in population in Slovakia and their potential importance in the aspect of public health

The aim of the research was to determine the prevalence of non-pathogenic protozoa circulating in the human population of Slovakia. We particularly focused on the socially deprived areas with poor sanitation conditions, as they are one of the factors affecting the transmission of these infections. Within this study, 2760 people were coprologically screened for the presence of protozoan cysts. The analyzed group comprised 1173 men and 1587 women from different regions of Slovakia. The total prevalence (2.03%) of non-pathogenic protozoa species was determined. The prevalence of Entamoeba coli was 0.80%, the prevalence of Endolimax nana 0.58%, and the prevalence of Blastocystis hominis was 0.65%. The presence of non-pathogenic protozoa was more frequent in women than that in men, in all age groups. The highest incidence of Entamoeba coli was found in children aged one month - seven years (0.79%), the lowest in the age group of 19-88 years (0.66%). Endolimax nana was most frequent in 8-18 year-olds (0.95%), where the statistical significance was found (p<0.05). The prevalence of Blastocystis hominis by the age group ranged from 0.39 to 0.95%. We did not find any statistical significance (p>0.05) for Entamoeba coli, and similarly for Blastocystis hominis associated with the sex and age. Although the circulation of non-pathogenic protozoa in the human population is far from being limited to the developing countries, their occurrence is also frequent in the population of developed countries. Despite their controversial pathogenicity, they should not be neglected, particularly in the patients with gastrointestinal symptoms.

Prevalence of intestinal parasitic infections and associated risk factors for hookworm infections among primary schoolchildren in rural areas of Nakhon Si Thammarat, southern Thailand

Background

Soil-transmitted helminth (STH) infections are among the most common type of infections worldwide and are widely distributed in tropical areas. In rural areas of southern Thailand where most land is used for agriculture, children are at risk of acquiring parasites, especially STHs. Assessing the current situation regarding parasitic infection in these areas is a prerequisite for developing appropriate control measures. This study is aimed at determining the prevalence of intestinal parasitic infections, the intensity of STH infections and the associated risk factors among primary schoolchildren in Nopphitam District, Nakhon Si Thammarat Province, Thailand.

Methods

A cross-sectional study involving 299 schoolchildren between 7 and 12 years of age was conducted between January and March 2016. A questionnaire administered by direct interviews was used to collect sociodemographic information and data on associated risk factors. Stool samples were processed using direct wet smears, formalin-ethyl acetate sedimentation concentration, and the modified Kato-Katz technique.

Results

The overall prevalence of intestinal parasites among the 299 children was 16% (48 of 299), with 32 children infected with hookworms (10.7%), 10 with Blastocystis hominis (3.3%), seven with Giardia intestinalis (1.6%), one with Enterobius vermicularis (0.3%), and one with Trichuris trichiura (0.3%). The hookworm infection intensity, measured by the median eggs per gram (EPG) of stool, was 1200 EPG (Interquartile range (IQR): 360–3200). Most children had light-intensity hookworm infections, but two had heavy-intensity infections. When participants included in the sample were classified by age, children 10–12 years old demonstrated higher intestinal parasite prevalence than those aged 7–9 years (adjusted odds ratio (AOR) = 2.3, 95% CI: 1.1–4.9, P = 0.030). Inadequate handwashing before meals was statistically associated with hookworm infections (AOR = 2.3; 95% CI: 1.1–4.8, P = 0.037).

Conclusions

This study highlights that hookworms are the most prevalent STH infection in the study area. Older age group (10–12 years) and inadequate handwashing before meals were statistically associated with hookworm infections. Accordingly, appropriate strategies and education on personal and environmental hygiene should be implemented. Moreover, the cost-effectiveness of mass drug administration in this area should be further investigated.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-6023-3) contains supplementary material, which is available to authorized users.

Prevalence and staining characteristics of Blastocystis isolates from food animals in Tamil Nadu

The present study was undertaken to investigate the prevalence and staining characteristics of Blastocystis isolated from food animals. Smears of the duodenal and caecal mucosal scrapings, collected from food animals, were stained with Giemsa, Gram's, modified acid-fast and acridine orange. Blastocystis was identified in 295 samples, including faeces and intestinal contents of animals like small ruminants (95), poultry (170) and pigs (30). The prevalence in pigs was found to be high (94.4%) followed by poultry (29.4%) and small ruminants (14%). Various forms of Blastocystis such as vacuolar, granular and amoeboid forms were identified by using different stains. The parasites stained with Giemsa were identified by the presence of eosinophilic nucleus and basophilic cytoplasm. In organisms stained with Gram's stain, the cytoplasm of the vacuolar forms took up the counter stain safranine. Blastocystis appeared as a pink colored cyst against bluish green background with modified acid-fast staining. The study shows that there is a very high prevalence of Blastocystis among the food animals investigated. Simple parasitological procedures, including direct microscopical examination and staining with agents like Giemsa, Gram's and acridine orange can assist identification of the parasites from intestinal contents and faecal material.

Prevalence of intestinal parasitic infection and associated risk factors among village health volunteers in rural communities of southern Thailand

Background

Intestinal parasitic infections remain prevalent and constitute a public health problem in certain rural areas of Thailand. Village health volunteers (VHVs), who are members of a Thai healthcare alliance, function as key providers of health prevention measures, disease control, and health education and share national health promotion campaigns with community members. This study is aimed at evaluating the prevalence, intensity, and risk factors for intestinal parasitic infection in VHVs in order to design community awareness and health education campaigns for the target population.

Methods

This cross-sectional study was conducted between January to April 2016 among village health volunteers (VHVs) from four sub-districts of Nopphitam District, Nakhon Si Thammarat Province, southern Thailand. Subjects for the study were selected using a simple random sampling method. Socio-demographic variables and risk factors were collected by a structured questionnaire. Stool specimens were collected and processed using direct wet mount and formol-ether concentration techniques to determine the presence of parasites and modified Kato-Katz thick smear to determine the intensity of infection.

Results

A total of 324 VHVs were enrolled. The overall prevalence of intestinal helminths was 9.3% (95% confidence interval [CI]: 6.3–13.0). The prevalence of hookworm, Strongyloides stercoralis, and Trichuris trichiura were 8.0% (95% CI: 5.3–11.5), 0.9% (95% CI: 0.2–2.7), and 0.3% (95% CI: 0–1.7), respectively. Mean intensity of hookworm infection was 1732 eggs per gram of stool. The prevalence was lower for protozoan infection than for helminth infection. Blastocystis hominis accounted for the highest percentage of intestinal protozoan infections 4.0% (95% CI: 2.2–6.8), followed by Giardia intestinalis 0.6% (95% CI: 0–2.2). No statistically significant difference was observed in the prevalence of intestinal parasitic infection among sub-districts (p > 0.05). Having dogs at home was associated with soil-transmitted helminth (STH) infection in study participants (Crude prevalence ratio [CPR]: 2.3; 95% CI: 1.0–5.2).

Conclusions

This study is the first to describe the prevalence of intestinal parasitic infection VHVs from southern Thailand. Hookworm infection is more prevalent than other types of STH infection. The development of community awareness campaigns and appropriate control measures should be considered to reduce the prevalence of hookworm infection, especially among VHVs who are the key persons providing health education to the community.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4486-2) contains supplementary material, which is available to authorized users.

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

Background

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

Methods and Principal Findings

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

Conclusion

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

First case of intestinal acariasis from Egypt

We are hereby reporting a case where the eggs and adults of the mold mites; Tyrophagus putrescentiae (Shrank) and the trophozoites of Blastocystis sp. were found in stool of three years old child from Minia City, Egypt. Intestinal mite infection was diagnosed after repeated identification of mite’ stages from six consecutive stool samples to exclude the possibilities of contamination and spurious infection. The patient was suffering from severe colicky abdominal pain and burning sensation around the anus one month ago. All other members of his family were having the same acarine in their feces, but were all symptomless. The patient was treated with ivermectin 200 µg/kg body weight once every 10 days for three doses. His cure indicated that he was having asymptomatic blastocystosis.

Prevalence of Intestinal Parasitic Infections in Jiroft, Kerman Province, Iran

BACKGROUND

Intestinal parasitic infections have a worldwide distribution. High prevalence of intestinal parasitic infections in individuals with low socioeconomic status and environmental conditions was found. No study has ever been conducted on the prevalence of these infections in Jiroft. Therefore, in this study prevalence of intestinal parasitic infections was evaluated in Jiroft, Kerman Province, Iran.

METHODS

A total of 1060 individuals from rural and urban areas of Jiroft were sampled accidentally, during 2013-2014. Fresh stool samples were collected from all individuals and examined by formalin ether concentration and agar plate culture. Direct examination was performed on watery samples.

RESULTS

Out of 1060 individuals, 563 (53.1%) and 497 (46.9%) people were from rural and urban areas, respectively. In general, 297 individuals (28%) were infected with intestinal parasites. The prevalence of infection for protozoa and helminthes infections were 27.4% and 1.8%, respectively. The most prevalent protozoans were Blastocystis hominis (13.7%) and Giardia lamblia (7.8%), and that of helminth was Hymenolepis nana (1.1%).

CONCLUSION

Intestinal protozoan parasites were more prevalent than helminth parasites. Source of water supply and personal hygiene were important factors in the distribution of parasites in the study area.

Blastocystissp. Infection Mimicking Clostridium Difficile Colitis

We report an unusual case of severe diarrhea related toBlastocystissp. infection in a patient with end stage renal disease on hemodialysis. The patient was admitted due to profuse diarrhea associated with fever and leukocytosis. Pertinent stool work-up such as leukocytes in stool, stool culture, clostridium difficile toxin B PCR, and serology for hepatitis A, hepatitis B, and hepatitis C and cytomegalovirus screening were all negative. Ova and parasite stool examination revealedBlastocystissp. The patient was given intravenous metronidazole with clinical improvement by day three and total resolution of symptoms by day ten.

Parasitic diarrheal disease: drug development and targets

Diarrhea is the manifestation of gastrointestinal infection and is one of the major causes of mortality and morbidity specifically among the children of less than 5 years age worldwide. Moreover, in recent years there has been a rise in the number of reports of intestinal infections continuously in the industrialized world. These are largely related to waterborne and food borne outbreaks. These occur by the pathogenesis of both prokaryotic and eukaryotic organisms like bacteria and parasites. The parasitic intestinal infection has remained mostly unexplored and under assessed in terms of therapeutic development. The lack of new drugs and the risk of resistance have led us to carry out this review on drug development for parasitic diarrheal diseases. The major focus has been depicted on commercially available drugs, currently synthesized active heterocyclic compounds and unique drug targets, that are vital for the existence and growth of the parasites and can be further exploited for the search of therapeutically active anti-parasitic agents.

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

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

The prevalence of Blastocystis hominis and other protozoan parasites in soldiers returning from peacekeeping missions

Blastocystis hominis is a common intestinal parasite found in humans living in poor sanitary conditions, living in tropical and subtropical climates, exposed to infected animals, or consuming contaminated food or water. The aim of this study was to determine the prevalence of B. hominis in Polish military personnel returning from peacekeeping missions in Iraq and Afghanistan. In total, 1,826 stool samples were examined. Gastrointestinal parasites were detected in 17% of the soldiers. The examined stool samples most frequently contained vacuolar forms of B. hominis (15.3%) and cysts of Entamoeba coli (1.0%) or Giardia lamblia (0.7%). In 97.1% of stool samples from infected soldiers, we observed less than five developmental forms of B. hominis in the field of view (40×). The parasite infections in soldiers were diagnosed in the autumn and the spring. There was no statistical correlation between age and B. hominis infection. Our results show that peacekeeping missions in countries with tropical or subtropical climates could be associated with risk for parasitic diseases, including blastocystosis.

Stress exacerbates infectivity and pathogenicity of Blastocystis hominis: in vitro and in vivo evidences

Background

Stress alters the oxidant-antioxidant state and immune cell responses which disrupts its function to combat infection. Blastocystis hominis, a common intestinal protozoan has been reported to be opportunistic in immunocompromised patients namely cancer. B. hominis infectivity in other altered immune system conditions especially stress is unknown. We aimed to demonstrate the stress effects towards the susceptibility and pathogenicity of B. hominis infection.

Methods/Findings

Three-week-old Wistar rats were divided into four groups: (a)control; (b)stress-induced; (c)B. hominis infected; (d)stress-induced with B. hominis infection; (n = 20 respectively). Stress was induced for an hour daily (30 days) using a Belly Dancer Shaker. Weight gain was monitored, stool samples were collected for B. hominis screening and blood for the determination of differential count, levels of immunoglobulin, oxidative damage, and peripheral blood mononuclear cell (PBMC) proliferation upon induction with solubilized antigen of B. hominis (Blasto-Ag). Group (b) exhibited the highest level of weight gain. Group (d) had higher levels of parasite cyst count in stools, serum IgE, oxidized protein and lipid compared to the group (c). Levels of monocyte and antioxidant in group (d) were decreased and their PBMCs showed highest inhibition of proliferation level when exposed to Blasto-Ag. Monocyte level in Group (b) showed insignificant difference compared to group (a) but was significantly lower compared to group (c). Antioxidant levels in group (c) were generally lower compared to group (a) and (b). Inhibition level exhibited by Blasto-Ag treated PBMCs of group (c) was higher compared to group (a) and (b).

Conclusion

The pathogenicity and augmentation of B. hominis infection is enhanced when stress is present. Lifestyles today are becoming increasingly stressed and the present findings suggest that the parasite which has been reported to be one of the most common organisms seen in stool surveys, namely in developing countries, may tend to be more pathogenic in stressful situations.

Prevalence of intestinal protozoa infection among school-aged children on Pemba Island, Tanzania, and effect of single-dose albendazole, nitazoxanide and albendazole-nitazoxanide

Background

Pathogenic intestinal protozoa infections are common in school-aged children in the developing world and they are frequently associated with malabsorption syndromes and gastrointestinal morbidity. Since diagnosis of these parasites is difficult, prevalence data on intestinal protozoa is scarce.

Methods

We collected two stool samples from school-aged children on Pemba Island, Tanzania, as part of a randomized controlled trial before and 3 weeks after treatment with (i) single-dose albendazole (400 mg); (ii) single-dose nitazoxanide (1,000 mg); (iii) nitazoxanide-albendazole combination (1,000 mg–400 mg), with each drug given separately on two consecutive days; and (iv) placebo. Formalin-fixed stool samples were examined for the presence of intestinal protozoa using an ether-concentration method to determine the prevalence and estimate cure rates (CRs).

Results

Almost half (48.7%) of the children were diagnosed with at least one of the (potentially) pathogenic protozoa Giardia intestinalis, Entamoeba histolytica/E. dispar and Blastocystis hominis. Observed CRs were high for all treatment arms, including placebo. Nitazoxanide showed a significant effect compared to placebo against the non-pathogenic protozoon Entamoeba coli.

Conclusions

Intestinal protozoa infections might be of substantial health relevance even in settings where they are not considered as a health problem. Examination of a single stool sample with the ether-concentration method lacks sensitivity for the diagnosis of intestinal protozoa, and hence, care is indicated when interpreting prevalence estimates and treatment effects.

Blastocystis hominis and Endolimax nana Co-Infection Resulting in Chronic Diarrhea in an Immunocompetent Male

Blastocystis hominis and Endolimax nana exist as two separate parasitic organisms; however co-infection with the two individual parasites has been well documented. Although often symptomatic in immunocompromised individuals, the pathogenicity of the organisms in immunocompetent subjects causing gastrointestinal symptoms has been debated, with studies revealing mixed results. Clinically, both B. hominis and E. nana infection may result in acute or chronic diarrhea, generalized abdominal pain, nausea, vomiting, flatulence and anorexia. We report the case of a 24-year-old immunocompetent male presenting with chronic diarrhea and abdominal pain secondary to B. hominis and E. nana treated with metronidazole, resulting in symptom resolution and eradication of the organisms. Our case illustrates that clinicians should be cognizant of both B. hominis and E. nana infection as a cause of chronic diarrhea in an immunocompetent host. Such awareness will aid in a timely diagnosis and possible parasitic eradication with resolution of gastrointestinal symptoms.

Intestinal parasitic infection detected by stool examination in foreign laborers in Kaohsiung

Most foreign laborers in Taiwan come from Southeast Asia, where public health is not as well funded as in Taiwan, and parasitic infections are still common. Therefore, we recruited foreign laborers to undergo examination for parasitic infection to determine the infection conditions and follow-up conditions in foreign laborers whose stools were found to be abnormal. A total of 7,360 foreign laborers were enrolled for stool examination in our hospital, and the merthiolate iodine formaldehyde method was used to diagnose intestinal parasite infection. In total, 331 (4.5%) foreign laborers were found to be infected, and Blastocystis hominis was identified as the most prevalent intestinal parasite (2.54%), followed by Trichuris trichiura (0.54%) and hookworm (0.53%). Parasite infection rates among laborers of different nationalities were also significantly different (p < 0.001). Forty-two intestinal-parasite-infected foreign laborers received anti-parasitic therapy in our hospital, and treatment was successful. Among the 154 intestinal-parasite-infected foreign laborers who did not receive treatment in our hospital but were later re-examined, 132 were parasite-free. B. hominis has been the most prevalent intestinal parasite infecting foreign laborers in Taiwan ever since it was added to the list of infections to be screened for stool examination by the Taiwan Centers for Disease Control in 2002. It is important to closely monitor, control and treat parasite-infected foreign laborers to minimize the danger to public health.

Parasitic infection in a young man presenting with non-specific abdominal pain

A 27-year-old man presented with a two-week history of central colicky abdominal pain associated with loose stools. Further history revealed that he had been exposed to contaminated waters. Stool investigation by direct wet stool smears revealed the presence of Entamoeba histolytica and Blastocystis hominis cysts. A diagnosis of amoebiasis secondary to E. histolytica and concurrent B. hominis infestation was made. We would like to emphasise the importance of clinical history including recent travel to endemic areas. Any suspicion of parasitic infection should prompt the clinician to investigate. Early diagnosis and management would prevent serious complications associated with E. Histolytica infection.

Six ulcerative colitis patients with refractory symptoms co-infective with Blastocystis hominis in China

Blastocystis hominis is an enteric parasite which has long been considered as an innocuous commensal living in the intestinal tract. Our research was to explore the role of B. hominis in refractory ulcerative colitis. Our department admitted 122 cases of ulcerative colitis patients. In these patients, there were 73 cases of patients who were responsive to sulfasalazinec, mesalazine in a standard dosage, according to the symptoms change. There was one patient who was detected to have B. hominis infection through stool detection. There were 49 patients with relapse symptoms. In this group, there were six patients who were detected with B. hominis infection through stool detection. The six patients of refractory ulcerative colitis were treated with metronidazole for 10-14 days. They almost completely recovered 3 weeks later. Patients diagnosed with ulcerative colitis should always consider this parasite infection when the symptoms are refractory and cannot be released.

Intestinal protozoan infections in relation to nutritional status and gastrointestinal morbidity in Colombian school children

While Giardia duodenalis infection has been consistently associated with nutrient malabsorption and stunting in children, the effects of other protozoans on nutritional status or gastrointestinal morbidity are less clear. We sought to determine whether infection with common intestinal protozoans including Giardia duodenalis, Entamoeba coli and Blastocystis hominis was associated with anthropometric and micronutrient status, gastrointestinal symptoms, visits to the doctor or school absenteeism in children 5-12 years of age from Bogotá, Colombia. We obtained stool samples from 442 children enrolled in primary schools in 2006 and examined the presence of intestinal protozoans in relation to height, body mass index, plasma concentrations of vitamins A and B12, ferritin and zinc and erythrocyte folate. In addition, we examined the associations between protozoan infections and the incidence of common gastrointestinal symptoms, which were registered prospectively in morbidity diaries. The prevalence rates of G. duodenalis, E. coli and B. hominis infection were 6.3, 23.1 and 22.4%, respectively. Giardia infection was associated with lower height-for-age z-score (p = 0.04), whereas E. coli infection was associated with low erythrocyte folate (p = 0.04), and B. hominis infection was related to higher vitamin A levels (p = 0.05). Infection with E. coli was also associated with a significantly higher incidence of fever but fewer visits to the doctor, while B. hominis infection was associated with significantly less diarrhea, diarrhea with vomiting, doctor visits and school absenteeism. In conclusion, G. duodenalis and E. coli infections were associated with indicators of poor nutritional status in this population, while B. hominis was related to apparently decreased morbidity.

Intestinal parasitic infections among intellectual disability children in rehabilitation centers of northern Iran

Parasitic infection is highly prevalent throughout the developing countries of the world. These infections are the major problem in rehabilitation centers for the mentally retarded. There have been many reports about the prevalence of parasitic infection among different groups of people in Iran; however, the epidemiological data in intellectual disability (ID) individuals are rare and there are no such data from northern Iran. The aim of the present study was to determine the incidence of intestinal parasitic infections among the inhabitants of rehabilitation centers of Mazandaran province, northern Iran. A triple fecal specimens was collected from each of the 362 participants (183 males, 179 females) residing in six rehabilitation centers of Behshahr, Sari, Amol, Nowshahr and Ramsar. Each specimen was examined by direct wet mounting, formol-ether concentration, Ziehl-Neelsen and trichrome permanent staining. The overall infection rate of intestinal parasite was 26.2% (95 out of 362 subjects; 22.4% in males and 30.2% in females). Giardia lamblia was the most commonly found protozoan parasite (8.0%) followed by Entamoeba coli (5.5%), Blastocystis hominis (3.3%), Endolimax nana (2.8%) and Entamoeba histolytica (1.7%). Double infections were E. coli and B. hominis (1.1%), G. lamblia and Chilomastix mesnili (1.1%), G. lamblia and B. hominis (0.5%), G. lamblia and E. coli (0.5%), E. histolytica and E. coli (0.5%), E. nana and E. coli (0.5%) and E. nana and B. hominis (0.5%). No egg-positive case was found. These helminthic parasites were found to be not common among the participants, 75% of whom had been treated with mebendazole by guardians as a tradition, every 6 months. Nevertheless, our data in rehabilitation centers in northern Iran suggest that infection is not higher than that in community population in recent years in this geographical area.

Sexual transmission of intestinal parasites in men who have sex with men

Direct oral-anal sexual contact is a common practice among men who have sex with men (MSM) and is implicated in the transmission of various enteric pathogens including intestinal parasites. The present study reviewed data on the sexual transmission of intestinal parasites among MSM, and highlighted advances in the diagnosis of such infections. The emergence and spread of intestinal parasites is of public health concern particularly in the homosexual community. Intestinal parasitic infection should be considered in the differential diagnosis of gastrointestinal disease in this population. Combination of traditional diagnostic procedures with implementation of testing based on novel molecular methods in the accurate identification of intestinal parasites is important so that early intervention and control of infection is facilitated.

Expression of interferon gamma and proinflammatory cytokines in the cecal mucosa of rats experimentally infected with Blastocystis sp. strain RN94-9

Blastocystis hominis is a zoonotic intestinal protozoan parasite whose pathogenic potential is still controversial. The aim of the present study was to clarify the pathogenicity of Blastocystis parasites in rats. Oral inoculation with 1 x 10(5) cysts of Blastocystis sp. strain RN94-9 in rats resulted in chronic infection in the cecum at least until 4 weeks after infection. Histological examination revealed neither mucosal sloughing nor inflammatory cell infiltration but showed a slight but significant increase in goblet cell numbers in the cecal mucosa 1-3 weeks post-infection. Differential staining of acidic and neutral mucins by the alcian blue-periodic acid-Schiff method showed that the predominantly increased cells were neutral mucin(+) but not acidic mucin(+) goblet cells. Reverse transcription real-time polymerase chain reaction studies demonstrated significant upregulation of the expression of interferon-gamma, interleukin (IL)-12, and tumor necrosis factor alpha, but not IL-6 or granulocyte-macrophage colony-stimulating factor, in the cecal mucosa at 2 and/or 3 weeks post-infection. The induction of local host responses, including mild goblet cell hyperplasia, and significant upregulation of type-1 and proinflammatory cytokines, suggest that Blastocystis sp. strain RN94-9 is a weakly pathogenic organism that could elicit proinflammatory as well as protective responses in local tissues.

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

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

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

SUMMARY

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

Detection of Blastocystis from stool samples using real-time PCR

We developed a real-time LC PCR assay to detect a 152 bp sequence in an uncharacterized region of the Blastocystis genome. The described assay detected 11 of 11 ATCC strains of Blastocystis from subtypes 1, 3, and 4. Three of three stool samples from Oregon and California military personnel that were negative for Blastocystis by an ova and parasite test as well as a conventional PCR assay were positive for Blastocystis using our real-time LC PCR assay. Diagnosis of Blastocystis infections using this sensitive method, including DNA extraction and real-time PCR, only requires 3 h. The lower limit of detection for Blastocystis in stool using the real-time LC PCR assay was calculated to be 760 cells of Blastocystis per 100 mg of stool, an estimated 760 parasites per reaction. The assay did not cross-react with Ruminococcus hansenii, Anarococcus hydrogenalis, Bifidobacterium adolescentis, Fusobacterium prausnitzii, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, or Lactobacillus acidophilus. Because of the ease of use, sensitivity, specificity, and increase in Blastocystis infections in the USA we believe this assay has the potential to be useful as a clinical diagnosis tool of Blastocystis infection.

Prevalence and Clinical Features of Blastocystis hominis Infection among Patients in Sebha, Libya

OBJECTIVE

To determine the prevalence and seasonal variation, and to assess the clinical manifestations and treatment of blastocystosis in Libyan patients.

METHODS

Three thousand six hundred and forty five stool samples were screened for Blastocystis hominis using normal saline and iodine solution preparations. The clinical features of 108 patients were described, in whom B. hominis was the only parasite isolated. Fifty symptomatic patients were treated with 1500 mg metronidazole daily for 7 days and their stools were re-investigated for B. hominis.

RESULTS

B. hominis was found in 969 (26.58 %) of 3645 stool specimens examined. The infection of B. hominis was significantly more (p < 0.05) in summer than in winter over a three year period. In a prospective study of 108 patients, the most common symptoms with stools positive only for B. hominis were diarrhoea (84.94 %), abdominal pain (66.66 %), flatulence (17.20 %) and vomiting (16.12 %). High concentration of B. hominis cells were found more in symptomatic patients than asymptomatic ones (9.20 cells per 40 X field versus 4.06 respectively) with statistically significant differences (p < 0.001). Patients with B. hominis responded to metronidazole and were fully cured after 7 days.

CONCLUSION

The occurrence of B. hominis infections in outpatients are probably related to weather conditions, with the suggestion that the hot, dry weather of the Sebha region favors the development and transmission of this organism. B. hominis infections might have a role in some pathological conditions, resulting in gastrointestinal symptoms.

Eosinophilia: Causes and pathobiology in persons with prior exposures in tropical areas with an emphasis on parasitic infections

Eosinophilia in patients exposed to tropical or subtropical environments is caused most commonly by helminth (worm) infections. Besides a detailed exposure history, the diagnostic approach must consider other infections and noninfectious causes of eosinophilia, as treatments for many of these disorders differ.

Parasites in nosocomial diarrhoea: are they underestimated?

Nosocomial diarrhoea, defined as diarrhoea occurring more than 72 h after hospital admission, is reported to account for <1% of endemic nosocomial infections and 17% of epidemic nosocomial infections. The yield of diagnoses from stool cultures in nosocomial diarrhoea is low, and information regarding the role of parasites is limited. We conducted a study to determine the responsible bacterial and parasitological pathogens from nosocomial diarrhoea cases in our 2000-bed tertiary care facility over a 16-month period. Of 226 patients, Clostridium difficile toxins A or B were present in 5.5%, giardia cysts and/or trophozoites in 4.4%, Blastocytis hominis in 4.4% and Cryptosporidium sp. in 0.5% of samples. In conclusion, parasites should be sought in nosocomial diarrhoea in endemic areas.

No correlation between clinical symptoms and Blastocystis hominis in immunocompetent individuals

Abstract Background and Aim: Previous reports regarding the clinical significance and pathogenicity of Blastocystis hominis have been contradictory. The aim of this study was to examine the association between Blastocystis and gastrointestinal symptoms in immunocompetent individuals.

METHODS

We monitored over 2800 healthy people for a period of 15 months, and took stool specimens during both asymptomatic periods and during periods of gastrointestinal symptoms.

RESULTS

After exclusion of individuals who had simultaneous identification of other fecal pathogens, we compared the proportions of asymptomatic versus symptomatic individuals positive for Blastocystis and found no significant difference (P = 0.5). Symptom status did not correlate with parasite abundance. We found that some individuals were likely to have Blastocystis detected during both asymptomatic and symptomatic periods, possibly suggesting carriage of the organism.

CONCLUSION

In conclusion, we found no correlation between clinical symptoms and the presence or absence of Blastocystis among this healthy cohort.

Blastocystis hominis, a long-misunderstood intestinal parasite

For over 50 years, Blastocystis hominis has been held to be a harmless intestinal yeast-probably frequent in stool samples from man and other primates, but usually ignored except as a possible source of confusion with Entamoeba histolytica. More recently, its status as a protozoan parasite has been accepted, and it is now increasingly recognized as an agent of intestinal disease - usually self-limiting but occasionally fatal in monkeys. Here, Charles Zierdt reviews the status o f this intriguing protozoan, drawing attention to its unusual biochemistry.

The effects of extracts from anti-diarrheic Thai medicinal plants on the in vitro growth of the intestinal protozoa parasite: Blastocystis hominis

The activities of n-hexane, dichloromethane and methanol extracts from five anti-diarrheic Thai medicinal plants, Acacia catechu (Fabaceae) resin, Amaranthus spinosus (Amaranthaceae) whole plant, Brucea javanica (Simaroubaceae) seed, Piper longum (Piperaceae) fruit and Quercus infectoria (Fagaceae) nut gall were tested against the in vitro growth of fresh isolates of the intestinal protozoan parasite, Blastocystis hominis. The extracts at concentrations that ranged from 62.5 to 2000 microg/mL, were incubated with several isolates of Blastocystis hominis for 48 h. The activities were classified as killed, inhibited, moderately inhibited and not-inhibited. Dichloromethane and methanol extracts from the Brucea javanica seed and a methanol extract from Quercus infectoria nut gall showed the highest activity. At a concentration of 2000 microg/mL, the three extracts killed 82, 75 and 67% of the Blastocystis hominis samples tested and inhibited 94, 100 and 76% of them, respectively. Metronidazole, used as a reference antiprotozoan drug, at a concentration of 40 microg/mL, killed 97% of the Blastocystis hominis isolates and inhibited all samples tested at concentrations that ranged from 1.25 to 20 microg/mL.

Blastocystis hominis and travelers

B. hominis is a unicellular protozoan commonly identified in stool specimens of travelers who have returned from tropical countries. It has a world-wide distribution, and infection is more common in developing countries compared to industrialized nations. Clinical features of illness which have been attributed to Blastocystis include nausea, anorexia, abdominal pain, flatulence and acute or chronic diarrhea. The preferred method of diagnosis is a permanently stained smear of an unconcentrated stool specimen. The presence of B. hominis in stool specimens of symptomatic travelers should prompt clinicians to search for other unrecognized co-pathogens. Due to controversy regarding the pathogenicity of B. hominis in humans, clinicians are often faced with the dilemma of whether or not they should offer treatment for B. hominis infection in returned travelers. The most commonly used drugs for treatment include metronidazole and trimethoprim-sulfamethoxazole (TMP-SMX), when treatment is deemed necessary. Prevention in travelers should focus on food and water precautions as the organism is transmitted by the fecal-oral route.

Blastocystis hominis as a cause of hypoalbuminemia and anasarca

The protozoan Blastocystis hominis has been considered nonpathogenic, but this classification has come under scrutiny in light of reports in the medical literature indicating it could be the cause of intestinal disorders and, in one case, hypoalbuminemia. Reported here is a severe case of infection with B. hominis that caused acute gastroenteritis with prolonged diarrhea, hypoalbuminemia and anasarca. The diagnosis was based on the parasitological finding, since no other pathological evidence was found. The patient responded favorably to treatment with metronidazole for 10 days. This case supports the idea that B. hominis should be considered as a cause of opportunistic infection in debilitated patients despite the controversy surrounding its pathogenicity.

[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.

Polyparasitism with Schistosoma mansoni, geohelminths, and intestinal protozoa in rural Côte d'Ivoire

Single species infections with schistosomes, geohelminths, and intestinal protozoans are common over large parts of sub-Saharan Africa, and it is expected that polyparasitism affects a considerable proportion of the population, hence posing a great toll on public health. However, few investigations have been carried out to quantify the extent of polyparasitism. Here, a detailed assessment is reported for the epidemiology of Schistosoma mansoni, geohelminths, and intestinal protozoan infections, with particular emphasis on polyparasitism among 260 community members in rural Cĵte d'Ivoire. Schistosoma mansoni, Entamoeba coli, and hookworm were the predominant species with prevalences of 71.5, 64.6, and 51.9%, respectively. Only 8 individuals displayed no infection, whereas two-thirds of the population harbored 3 or more parasites concurrently. There were a series of significant pairwise parasite co-occurrences, e.g., between S. mansoni and hookworms and between S. mansoni and E. coli. It is concluded that polyparasitism in the population studied here was very common, which is probably the case also in other areas of rural Cĵte d'Ivoire and elsewhere in sub-Saharan Africa. These findings call for integrated approaches to effectively control multiple parasitic and protozoan infections.

Effect of trimethoprim-sulfamethaxazole in Blastocystis hominis infection

OBJECTIVE

Blastocystis hominis (B. hominis) is a common intestinal parasite that has long been considered nonpathogenic. Recently there have been many reports supporting a role for the organism as a potential pathogen. We performed a study to examine the pathogenicity of B. hominis and the effect of trimethoprim-sulfamethaxazole (TMP-SMX) on this organism.

METHODS

Stool samples of patients, who came to the Department of Parasitology, Faculty of Medicine, Celal Bayar University, were examined by direct wet-mount, trichrome staining, formalin-ethyl acetate concentration, and Kinyoun acid fast techniques for intestinal parasites, and bacteriological stool cultures were performed. Fifty-three symptomatic patients (38 children and 15 adults) with two consequent stool samples positive for abundant B. hominis (five or more organisms per x400 field) and negative for other parasitic and bacterial pathogens were treated with TMP-SMX for 7 days, children 6 mg/kg TMP, 30 mg/kg SMX, and adults 320 mg TMP, 1600 mg SMX, daily. On the seventh day, at the end of treatment, stool samples of all patients were examined by same methods, and clinical symptoms were again evaluated.

RESULTS

B. hominis was eradicated in 36 of 38 (94.7%) children, and 14 of 15 (93.3%) adults. Clinical symptoms disappeared in 39 (73.6%), decreased in 10 (18.9%), and no change was observed in one (1.9%) patient, whereas symptoms persisted in all three (5.7%) patients in whom B. hominis could not be eradicated. Mean number of stools per day was significantly decreased from 4.3 to 1.2 in the 33 children (p < 0.001), and decreased from 3.5 to 1.0 in the four adults (p = 0.06) with diarrhea.

CONCLUSIONS

These results suggested that B. hominis may be pathogenic, especially when it is present in large numbers, and TMP-SMX is highly effective against this organism. Although there are some anecdotal reports, to our knowledge this is the first study examining the effect of TMP-SMX on B. hominis in humans.