Seasonal cholera from multiple small outbreaks, rural Bangladesh.

Clinical and environmental Vibrio cholerae organisms collected from February 2004 through April 2005 were systematically isolated from 2 rural Bangladeshi locales. Their genetic relatedness was evaluated at 5 loci that contained a variable number of tandem repeats (VNTR). The observed minimal overlap in VNTR patterns between the 2 communities was consistent with sequential, small outbreaks from local sources.

Enterotoxigenic Bacteroides fragilis-associated diarrhea in children 0-2 years of age in rural Bangladesh.

The burden of enterotoxigenic Bacteroides fragilis (ETBF)-related diarrhea was determined in a birth cohort of 252 children in rural Bangladesh. Isolation rates of ETBF in stool and risk factors for acquisition of ETBF and disease were established. Of 382 B. fragilis-positive specimens, 14.4% of the strains found in them produced enterotoxin, as determined by a tissue-culture assay. The overall isolation rate of ETBF was 2.3% (40/1750) from diarrheal specimens and 0.3% (15/5679) from nondiarrheal specimens collected throughout the 2 years of the study (P < .001). ETBF was isolated from 20.3% (40/197) of the B. fragilis-positive diarrheal specimens and from 8.1% (15/185) of the B. fragilis-positive nondiarrheal specimens (P < .001) and was significantly associated with acute diarrheal disease in children > or = 1 year of age (P = .0001). The diarrheal illness was mild in nature. In conditional multivariate analyses that examined environmental and host risk factors, the presence of livestock in the household area was linked to the acquisition of ETBF (chickens, P < .05; cows, P = .06). ETBF was found to be a small but significant contributor to diarrheal disease in this rural community. Improved management of livestock may be useful for the prevention of ETBF infection.

Critical factors influencing the occurrence of Vibrio cholerae in the environment of Bangladesh.

The occurrence of outbreaks of cholera in Africa in 1970 and in Latin America in 1991, mainly in coastal communities, and the appearance of the new serotype Vibrio cholerae O139 in India and subsequently in Bangladesh have stimulated efforts to understand environmental factors influencing the growth and geographic distribution of epidemic Vibrio cholerae serotypes. Because of the severity of recent epidemics, cholera is now being considered by some infectious disease investigators as a "reemerging" disease, prompting new work on the ecology of vibrios. Epidemiological and ecological surveillance for cholera has been under way in four rural, geographically separated locations in Bangladesh for the past 4 years, during which both clinical and environmental samples were collected at biweekly intervals. The clinical epidemiology portion of the research has been published (Sack et al., J. Infect. Dis. 187:96-101, 2003). The results of environmental sampling and analysis of the environmental and clinical data have revealed significant correlations of water temperature, water depth, rainfall, conductivity, and copepod counts with the occurrence of cholera toxin-producing bacteria (presumably V. cholerae). The lag periods between increases or decreases in units of factors, such as temperature and salinity, and occurrence of cholera correlate with biological parameters, e.g., plankton population blooms. The new information on the ecology of V. cholerae is proving useful in developing environmental models for the prediction of cholera epidemics.

A 4-year study of the epidemiology of Vibrio cholerae in four rural areas of Bangladesh.

How Vibrio cholerae spreads around the world and what determines its seasonal peaks in endemic areas are not known. These features of cholera have been hypothesized to be primarily the result of environmental factors associated with aquatic habitats that can now be identified. Since 1997, fortnightly surveillance in 4 widely separated geographic locations in Bangladesh has been performed to identify patients with cholera and to collect environmental data. A total of 5670 patients (53% <5 years of age) have been studied; 14.3% had cholera (10.4% due to V. cholerae O1 El Tor, 3.8% due to O139). Both serogroups were found in all locations; outbreaks were seasonal and often occurred simultaneously. Water-use patterns showed that bathing and washing clothes in tube-well water was significantly protective in two of the sites. These data will be correlated with environmental factors, to develop a model for prediction of cholera outbreaks.