Epidemiology and pathogenicity of Blastocystis hominis

Abstract

A prospective study was performed on a large outpatient population to evaluate the epidemiology and pathogenicity of Blastocystis hominis. Patients with stool specimens positive for B. hominis and negative for other bacterial and parasitic pathogens were sent a questionnaire and were requested to submit a follow-up specimen for ova-and-parasite examination. B. hominis was identified in 530 of 16,545 specimens (3.2%). There was a spectrum of clinical-pathological presentations in the 143 patients evaluated. An asymptomatic carrier state was seen in 19 patients. Fifteen patients had an illness consistent with acute self-limited B. hominis gastroenteritis, and 21 patients had chronic gastroenteritis associated with B. hominis. In the epidemiological evaluation of 130 patients, the most common symptoms were watery diarrhea, abdominal pain, and gas. We did not find a statistically significant association between the number of organisms present and the disease state. In summary, our results are consistent with a role for B. hominis in acute and chronic gastroenteritis; however, further detailed studies are necessary to determine whether that role is one of association or causation.

Intestinal parasitic infection and associated symptoms in children attending day care centres in Trujillo, Venezuela

“…The pathogenic potential of some intestinal parasites is well established, while others may or may not cause symptoms, depending on the host immune status and other factors. Among the protozoa, Giardia duodenalis and Entamoeba histolytica have been associated with persistent and acute diarrhoea (Utzinger et al 1999;Newman et al 2001), while Blastocystis hominis and Cryptosporidium parvum tend to cause marked symptoms primarily in immunocompromised hosts (Doyle et al 1990;Chacin-Bonilla et al 1993). Entamoeba dispar, a protozoan morphologically identical to E. histolytica, is a nonpathogenic gut commensal (Reed 1995).…”

Isoenzyme patterns of Blastocystis hominis patient isolates derived from symptomatic and healthy carriers

“…The prevalence of B. hominis in man is between 1.6 and 16% in industrialized countries (Sheehan et al 1986;Sun et al 1989) and more than 50% in developing countries (Ashford & Atkinson 1992;Torres et al 1992). The pathogenic potential of B. hominis is still a matter of discussion (Doyle et al 1990;Garavelli et al 1991;Kain et al 1987;Markell & Udkow 1986;Miller & Minshew 1988;Senay & MacPherson 1990;Sun et al 1989). Some authors do not believe in pathogenic effects caused by B. hominis due to the unspecific symptoms, which are acute or chronic diarrhoea and other enteric symptoms.…”

Blastocystis hominis colitis in a haemophilic patient as a cause of lower gastrointestinal bleeding

“…This antibiotic may show activity against other pathogens so it has been hypothesized that its success may be due to clearance of either B. hominis or other frequently associated microorganisms; actually in some 26% of cases stool samples can be positive for another enteric infectious agent (bacteria or parasites, mainly amoebae) [1]. Cotrimoxazol and paromomycin can be regarded as alternative therapies in cases of unresponsiveness or intolerance to metronidazole [2]. The parasite is extremely resistant to environment conditions and even to antiprotozoal drugs in its cystic form.…”

“…Blastocystis hominis is an enteric parasite which has long been considered as an innocuous commensal living in the intestinal tract [1]; it can be found throughout the world. Unlike morphology many issues regarding pathogenicity, vital cycle, taxonomy, form used for transmission, treatment or molecular biology of this parasite remain unclear [2]; a faecal-oral transmission by contaminated water or food has been advocated to be the most important although this issue has not been experimentally confirmed [2].…”