Association of Blastocystis hominis with human disease

Blastocystis spp., Cryptosporidium spp., and Entamoeba histolytica exhibit similar symptomatic and epidemiological patterns in healthcare-seeking patients in Karachi

In this study, we collected data on the incidence of enteric parasites in healthcare-seeking individuals along with their symptoms to quantify the potential roles of factors such as age, sex, and seasonality in infection. We performed analysis to identify factors which could help differentiate parasitic infection from other causes of gastrointestinal illness in a community. The size of the patient population (n = 339), patient selection methodology, collection methods, and statistical analysis followed approaches from similar studies in core clinical journals. Ethical approval was obtained from the University of Karachi's Ethical Review Board. Fecal specimens (n = 339) submitted by symptomatic patients were collected from two clinical laboratories, along with information about the patients' age, sex, and symptoms. We found that symptoms of fever, vomiting, and constipation were 100 % predictive of finding a parasitic infection, while diarrhea was 88 % predictive of a parasitic infection. Gastrointestinal parasite-positive patients reported diarrhea (~60 %), vomiting (~30 %), fever (~25 %) and constipation (~25 %), while parasite-negative patients exhibited a symptomatic profile without fever, vomiting, and constipation. The distribution of symptoms in parasite-positive patients remained relatively invariant regardless of the parasite identified. Blastocystis spp.-mono-infected patients reported a similar profile to patients positive for Entamoeba histolytica/Entamoeba dispar and Cryptosporidium spp. Most parasitic infections exhibited a strong seasonal pattern, with a peak incidence in summer months. Infection by Blastocystis spp. was the most prevalent, and it was the only infection mathematically correlated to rainfall by Pearson's method. We observed no increase in healthcare-seeking behavior following a stressful community event, namely, the attempted assassination of Benazir Bhutto in Karachi. The data suggest that parasitological testing would produce a high yield of positive results when performed on healthcare-seeking patients in Karachi in 2007 with symptoms of fever, vomiting, or constipation and a low yield when performed on patients noting only abdominal pain. Parasitological testing also produces a higher yield on patients seen in summer months.

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.

Blastocystis hominis revisited

Blastocystis hominis is a unicellular organism found commonly in the intestinal tract of humans and many other animals. Very little is known of the basic biology of the organism, and controversy surrounds its taxonomy and pathogenicity. There morphological forms (vacuolar, granular, and ameboid) have been recognized, but recent studies have revealed several additional forms (cyst, avacuolar, and multivacuolar). The biochemistry of the organism has not been studied to any extent, and organelles and structures of unknown function and composition are present in the cells. Several life cycles have been proposed but not experimentally validated. The form used for transmission has not been defined. Infections with the organism are worldwide and appear in both immunocompetent and immunodeficient individuals. Symptoms generally attributed to B. hominis infection are nonspecific, and the need for treatment is debated. If treatment appears warranted, metronidazole is suggested as the drug of choice, although failures of this drug in eradicating the organism have been reported. Infection is diagnosed by light microscopic examination of stained smears or wet mounts of fecal material. Most laboratories identify B. hominis by observing the vacuolar form, although morphological studies indicate that other forms, such as the cyst form and multivacuolar form, also should be sought for diagnosis.