Are the environmental niches of Vibrio cholerae O139 different from those of Vibrio cholerae O1 El Tor?

BACKGROUND: Vibrio cholerae are known to be normal inhabitants of surface water. However, the environmental niches of the different strains of cholera are not well known, and therefore, populations at risk for cholera outbreaks cannot be clearly identified. METHODS: This study identifies environmental risk factors for cholera caused by V. cholerae O1 El Tor and O139 and environmental niches of the two strains present in Matlab, a cholera endemic area of Bangladesh. The study year was 1993, the year that the O139 strain first appeared in the study area. Patients who had either strain of cholera identified in a laboratory were included in the study. A geographic information system was used to map the household locations of the patients, to describe the human sanitary environment and population density, and to address potential anthropogenic and environmental risk factors of the disease. Spatial point pattern and exploratory spatial data analysis techniques were used to define the environmental niches of the two cholera strains. RESULTS: The study suggests the niches of O1 El Tor and O139 strains of V. cholerae appear to be similar, based on common environmental risk factors. CONCLUSIONS: The results of this study support a theory that O1 El Tor could possibly be replaced by the newer O139 strain in the future.