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 at the National Taiwan University report on a case history of a 34-year old Filipino man who developed heart failure following heart valve surgery. The heart failure was followed by persistent diarrhea and sepsis. Infectious disease testing, which included testing for viruses, E. histolytica, and C. diff failed to identify any pathogen other than Blastocystis. Symptoms resolved following treatment with metronidazole. The paper was published in the International Journal of Surgical Case Reports.
Blastocystis has at times been called a non-pathogenic yeast, so researchers at the University of Singapore put that claim to the test, by comparing the response of Blastocystis to the intestinal yeast Saccharomyces Boulardi. Their study reports that exposure of intestinal samples from mice to Blastocystis produces a significant amount of up-regulation of inflammatory chemicals, including interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α). The study found that production of the inflammatory factors in macrophages was caused primarily by up-regulation of factor ERK in cells, as inhibition of ERK significantly suppressed both mRNA and protein expression of IL-6 and TNF-α and mRNA expression of IL-1β. Exposure of cells to Saccharomyces Boulardi did not produce that effect. The study also examined experimental animal infection with Blastocystis sp. subtype 7 on mice, and found increased rate of inflammation, but that was not statistically significant [in contrast to earlier study by El-Wakil]. The researchers suggested that pre-treatment of mice with Dextran Sulfate, which was intended to emphasize potential Blastocystis pathology, may have negated the effect of Blastocystis. The study was published in Infection and Immunity.
A study of Blastocystis in a commercial pig herd and an immunosuppressed research herd shows a high prevalence of Blastocystis sp. subtype 5 in those groups. The researchers report that this particular species is likely host-adapted to pigs. Examination of intestinal biopsies from the pigs show no apparent signs of pathology or invasiveness, with Blastocystis cells appearing on the surface of the intestines in samples examples. The study was published in PLOS-One.
A study of Blastocystis infection in the Irish using sensitive DNA analysis techniques shows an overall prevalence of 56% in a point-prevalence study of 105 asymptomatic individuals. A separate smaller study tracked Blastocystis infection in 5 asymptomatic and showed the presence and subtype of infection remained consistent over at least 5 years. The study was published in FEMS Microbiology Ecology.
Researchers in Turkey studying results from examination of 111,889 stool samples report an overall prevalence of 5% (5486/111,889) in stool samples examined. The majority of positive samples showed Giardia, with Ascaris lumbricoides, and Blastocystis hominis: 16%, 7%, and 6%, respectively. Between 2000 and 2012, a highly significant reduction in general parasite prevalence was determined, compared to the 1988 and 2000 time period (p<0.001). The study was published in the Turkish Journal of Parasitology.
For many first world travelers, a trip to the tropics ends in diarrhea, which can be challenging for physicians to diagnose, due to the large number of organisms that can cause that illness. Researchers in Switzerland report some success with the use of a multiplex nucleic acid test in identifying pathogens in returning travelers, both adults and children. Although the multiplex test did not cover Blastocystis, results suggest that this might be an appropriate addition to the assay. The test was more successful at identifying pathogens in children, with 52% of samples from children showing positives, with rotavirus being the most common at 27%. Adult samples were positive only 11% of the time, but a separate microscopic examination showed Blastocystis infection in 23% of those individuals. The study was published in the journal Infection.
Researchers studying nuclear genes in Blastocystis report that a large number of those genes require a process known as mRNA polyadenylation to create functional termination codons, a process necessary for correct cell functioning. This process is somewhat unique in the animal world, found in Blastocystis and a few other organisms, but rarely in human genes. Although the authors did not note the treatment potential, a number of other researchers have studied mRNA polyadenylation as a treatment target for HIV, and even endometriosis, suggesting that this might one day be investigated as a treatment for Blastocystis infection. The study was published in Genome Biology and Evolution.
Researchers studying Blastocystis prevalence and transmission in Calarca’ Columbia report that children in public daycare environments have a high rate of Blastocystis infection, measured at 57.5%. While both Blastocystis-positive and Blastocystis-negative children reported a high rate of diarrhea, children with Blastocystis reported a significantly increased rate (45% vs. 33%, p < 0.05). Blastocystis infection was correlated with the presence of Blastocystis in a sugar cane beverage, drinks other than bottled milk, and foods. The study was published in Biomedia.
Although some infections occur with a consistently higher prevalence in less industrialized areas, Blastocystis sometimes breaks that rule. Researchers comparing Blastocystis infection in pig farmers in Southeast Queensland Australia to Cambodia report an infection rate of 83.3% in SEQ, vs. 55.2% in Cambodian villagers. Pigs in SEQ were more likely to be infected with Blastocystis, with 76.7% of the Austrian pigs infected vs. 45.2% of Cambodian pigs. Even more interesting, although both groups of pigs were infected predominantly with Blastocystis sp. subtype 5, that subtype was not found in Cambodians, but was found in the Austrians, suggesting that transmission from pigs to humans occurs in SEQ but not Cambodia. The study was published in Veterinary Parasitology.
An Austrial study of pigs reports that 81.5% of animals studies showed fecal IgA response to Blastocystis antigens. Immunosuppressed pigs were significantly more likely to show a response to Blastocystis antigens than immunocompetent pigs. Fecal IgA response has previously been studied in humans, but this may be one of the first studies on animal response. The researchers noted that since pigs infected with Blastocystis do not show intestinal pathology, a trait shared with many humans infected with Blastocystis, those animals may provide a good model for some human infections. The study was published in Parasite Immunology.