Is Blastocystis hominis a cause of diarrhea in travelers? A prospective controlled study in Nepal.

Although the pathogenicity of Blastocystis hominis has been extensively debated in the medical literature, controlled studies of the association between B. hominis and diarrhea are lacking. We conducted a case-control study among expatriates and tourists in Kathmandu, Nepal, in which we compared the prevalence of the organism among patients with diarrhea to that among a control group without diarrhea. B. hominis was detected in 56 (30%) of 189 patients with diarrhea, compared with 40 (36%) of 112 asymptomatic controls. Patients with diarrhea were significantly more likely to have > or = 10 B. hominis organisms per high-power (400x) field than were controls. However, among the 25 patients with this concentration of organisms, other enteric pathogens were detected in 17 (68%). Only 8 (4%) of 189 patients with diarrhea had > or = 10 B. hominis organisms per high-power field detected in the absence of other pathogens, compared with 5 (5%) of 112 asymptomatic controls. Thus, B. hominis in higher concentrations was not associated with diarrhea. There were no specific symptoms associated with B. hominis infection, and the presence of higher concentrations of the organism in stool was not associated with more-severe symptoms. Despite the high prevalence of the organism among travelers and expatriates in Nepal, the results of this study suggest that B. hominis does not cause diarrhea in this population.

Placebo-controlled trial of co-trimoxazole for Cyclospora infections among travellers and foreign residents in Nepal.

Cyclospora is a coccidian (previously referred to as cyanobacterium-like bodies) that has been implicated in cases of prolonged diarrhoea. The average duration of symptoms is more than three weeks, and no specific treatment has been shown to shorten the illness. A case report suggested that co-trimoxazole may be effective. Expatriate persons with gastrointestinal complaints and cyclospora detected on examination of faeces were recruited from two clinics in Kathmandu, Nepal, between May and August, 1994. Participants were assigned in a randomised, double-blinded manner to receive either cotrimoxazole (160 mg trimethoprim, 800 mg sulphamethoxazole) or placebo tablets twice daily for 7 days. Of 40 patients included in the study, 21 received cotrimoxazole and 19 placebo. There were no significant differences between these two groups in age, sex, time in Nepal, duration or severity of illness, or presence of other enteric pathogens. After 3 days, 71% of patients receiving co-trimoxazole still had cyclospora detected, compared with 100% of patients receiving placebo (p = 0.016). After 7 days, cyclospora was detected in 1 (6%) of 16 patients treated with co-trimoxazole who submitted stool specimens compared with 15 (88%) of 17 patients receiving placebo (p < 0.0001). Eradication of the organism was correlated with clinical improvement. There was no evidence of relapse of infection among treated patients followed for an additional 7 days. Treatment with co-trimoxazole for 7 days was effective in curing cyclospora infection among an expatriate population in Nepal.

Epidemiology of diarrhoeal illness associated with coccidian-like organism among travellers and foreign residents in Nepal.

A newly described organism called CLB (coccidian-like or cyanobacterium-like body) has been identified in cases of prolonged diarrhoea. To confirm an association of CLB with disease and identify risk factors for transmission, we conducted a case-control study of travellers and foreign residents at two outpatient clinics in Kathmandu, Nepal. Patients without diarrhoea were matched to CLB cases by clinic and date of visit. For comparison, patients with other causes of diarrhoea were also studied. Stools were examined for enteric pathogens with standard microbiological and molecular genetic techniques. CLB was identified in 108 (11%) of 964 individuals with gastrointestinal symptoms compared with only 1 (1%) of 96 symptom-free controls (p = 0.003). 7% of residents in the US Embassy community acquired the infection. The diarrhoeal illness associated with CLB lasted a median of 7 weeks (interquartile range 4-9) compared with 9 days (4-19) for individuals with other causes of diarrhoea (p < 0.0001). The prevalence of other enteric pathogens was no higher among CLB cases than among symptom-free controls. Patients with CLB infection were more likely than controls to report consumption of untreated water (odds ratio 3.98; 95% CI 1.29-13.14); organisms of the same appearance were identified in an epidemiologically implicated water sample. The significant association of CLB with prolonged diarrhoea, and the low rate of other enteropathogens in CLB cases, strongly supports the hypothesis that CLB is a new pathogen. Epidemiological and environmental data suggest that the organism is waterborne.