About Blastocystis

Blastocystis is a highly prevalent single-celled parasite that infects the gastrointestinal tract of humans and animals.  It has become the most prevalent gastrointestinal parasitic infection in developed and many developing countries, and it will produce long-term diarrhea, abdominal pain, and other symptoms in healthy individuals.

BRF’s web site has written and audio descriptions from patients, information on the newest research in diagnosis and treatment of Blastocystis ’hominis’ infection, and information on BRF”s advocacy program.

Researchers Identify Blastocystis Subtype Profiles from College Students

Researchers examining Blastocystis isolates from 53 college students report that Blastocystis sp. subtype 3 was the most common (32.1%, 17/53), followed by subtype 7 (9.4%, 5/53), subtype 1 (7.6%, 4/53), subtype 4 (7.6%, 4/53) and subtype 6 (1.9%, 1/53).  Subtypes 2 and 5 were not detected in the populations, and 22 subtypes could not be classified by the method used (STS primer amplification).  The abstract of the study is available on Pubmed.

Thermal Stress Leads to Fast Blastocystis Growth Rates

Blastocystis cells exposed to thermal stress (exposure to a temperature of 41C) exhibited higher levels of heat shock protein 70, and faster growth rates.  The full text of the study published by researchers from the University of Malaysia is available from the journal PLOS-One.

Blastocystis Antigens Induce IL-1B, IL-6, and TNF-alpha Expression in Murine Intestinal Explants

Researchers from the National University of Singapore have published a study in the journal Infection and Immunity reporting that Blastocystis antigens produce statistically significant increases in expression of proinflammatory cytokines such as IL-1Beta, IL-6, and TNF-alpha in mouse intestinal explants.   Serine proteases produced by Blastocystis were found to play a significant role in ERK and cytokine expression in the murine cells.  The text of the study is available from Infection and Immunity.


Animal Contact May Results in Different Transmission Dynamics between Developed and Rural Populations

A multi-institutional study performed between researchers in Australia, Denmark, and Thailand reported that although Blastocystis sp. subtype 5 transmission from pigs may be population-specific.  Blastocystis infection in pigs in both Southeast Queensland (SEQ) Australia, and a rural village in Cambodia was found to be similar, with both groups harboring exclusively Blastocystis sp. subtype 5 at rates of 76.7% and 45.2% respectively.  However, only the animal handlers in Australia were found to be infected with Blastocystis sp. subtype 5, and Australian animal handlers were infected at a higher rate than Cambodian villagers.  The infection rates in the SEQ piggery staff was reported to be 83.3%, vs. 55.2% in the Cambodian villagers.  The text of the paper is available from Veterinary Parasitology.

IBS Patients Infected with Blastocystis Show Statistically Significant Immune Differences

Some Irritable Bowel Syndrome (IBS) patients can be shown to have Blastocystis infection, while others do not, so there is a question as to whether the finding is clinically significant, and if scientific investigation of the Blastocystis infection would yield promising results.  Researchers at Aga Khan University analyzing Peripheral Blood Mononuclear Cells (PBMC) have identified which cytokines are produced in significantly different levels in IBS patients infection with Blastocystis.  The study analyzed PBMC’s from 80 D-IBS (diarrhea predominant IBS patients) without Blastocystis infection, with Blastocystis sp. subtype 1, and with Blastocystis sp. subtype 3.  The researchers reported that although IL-8 expression was similar in the groups,  in Blastocystis sp. subtype 1, IL-8 mRNA expression was increased compared with subtype 3 and controls (P=0.001).   A statistically significantly lower level of IL-10 was found in PBMC’s from D-IBS infected with Blastocystis sp. subtype 1, when compared to controls and Blastocystis sp. subtype 3 (P<0.001), and this low IL-10 production was associated with lymphocyte and plasma cell infiltration (P=0.015 and 0.002 respectively).  In both Blastocystis sp. subtype 1 and 3, IL-12 was associated with goblet cell depletion.  The full study is available in the journal Parasitology.

Blastocystis Plus Stress (but not stress alone) Produces More Significant Immune Inhibition

A number of researchers have suggested that gastrointestinal disease may be due to infection, stress, or a combination of both, but disentangling these causes can be difficult, as classical scientific method of controlled experimentation is not feasible with human subjects.  Researchers at the University of Malaysia have reported results from an animal study that was able to shed some light on the topic.  Three-week old Wistar rats were divided into four groups, mainly and subjected to (a) no stress or infection (control); (b) stress alone; (c) infection with Blastocystis alone; and (d) both stress and infection with Blastocystis.  The study reported that while the stress group gained more weight, there were no significant immunological differences between the stress and control group.  The group infected with Blastocystis showed lower levels of oxidants.  Additionally, infection with Blastocystis was associated with lower peripheral blood mononuclear cell counts.  The group exposed to stress and Blastocystis infection had higher levels of parasite count in stool samples, serum IgE, and oxidized protein compared to the Blastocystis group alone.  The full paper is available from PLOS-One.

Co-culture of Blastocystis and human epithelial cells suggests mechanism for gastrointestinal disease

Researchers working at the University of Singapore report that co-culture of human epithelial cells with Blastocystis sp. subtype 7 (but not Blastocystis sp. subtype 4) results in a statistically significant increase in apoptosis (spontaneous cell death) and produces changes in epithelial resistance, permeability, and tight junction localization.  The full text of the study is available from Biomed Research International.  

Large study (n=10,466) reports statistically higher incidence of low serum iron, high c-reactive protein, and occult blood in Blastocystis-positive patients

A study of 10,466 patients seen at an Iran hospital reports that patients with stool samples positive for Blastocystis infection were statistically more likely to have low serum iron levels.  Additionally, occult blood was positive in 0.93% of Blastocystis-positive cases, and none of the control (p < 0.05).  C-reactive protein was positive in 1.46% of the cases and 0.5% of controls.  Erythrocyte sedimentation rate level was significantly higher in cases with Blastocystis infection as well (p < 0.05).  The full free text is available from Przeglad Gastroenterology.

Researchers from St. Vincent’s Hospital in Australia have published a review and update on the pathogenic potential and treatment options for Blastocystis infection.  The paper describes a number of patient cases, summarizes current information on the life cycle and pathology of Blastocystis infection, and notes that many of the currently used treatments may provide a low degree of success in eradicating the infection.  The full free text is available from Gut Pathogens.

Blastocystis isolates from symptomatic humans behave differently from those from asymptomatic individuals

Researchers from the University of Malaysia report that Blastocystis cultures from symptomatic individuals report different behavior with respect to capase-like proteases.  Fluorescence intensity for active capase-like proteases was significantly greater in isolates from symptomatic individuals in the 72-hour in vitro culture (p < 0.001).  Treatment with metronidazole inhibited the capase activation.  The full free text is available from Parasites and Vectors.