Epidemiology and Ecology of V. cholerae in Bangladesh

Cholera continues to cause significant morbidity and mortality throughout the developing world. The primary objective of the original proposal was to test the hypothesis that environmental factors involving surface waters were responsible for the observed periodicity and pandemic nature of cholera. Data collected from our pervious study (2003 -2007) strongly suggest, that environmental factors are predictive of cholera outbreaks. Work will now focus on the positive associations that were found, and comparing the V. cholerae strains isolated from the environment and those from patients. With our successes to date, we will continue clinical and environmental surveillance in association with ICDDR,B, the University of Maryland Biotechnology Institute and School of Medicine, and Emory University and Johns Hopkins University, Bloomberg School of public Health, USA. Clinical and environmental surveillance will continue at Mathbaria one of the original sites near the Sundarbans, area of mangrove swamps close to the Bay of Bengal. We have replaced Bakerganj by Chhatak, which is situated in the north eastern part of the country. These two widely separated geographical sites have documented different seasonal cholera outbreaks. We will continue to use assays which will focus on 1) identifying V. cholerae (both culturable and viable but not culturable cells (VBNC) in surface waters, using both standard techniques and colony blots with non-radioactive DNA probes (for V. cholerae species, O1, O139, ctx, and tcpA) DNA extraction, and PCR, 2) assessing the relationship between clinical and environmental isolates by genotyping (using AFLP, ERIC-PCR, and MLST) and 3) identifying and enumerating V. cholerae attached to plankton using direct fluorescent antibody techniques, and fluorescent in-situ hybridization assays. Using improved assays, developed during the course of current study we will determine genetic associations between clinical and environmental isolates which will enable us to establish key epidemiological relationships that have been difficult to document at the genomic level. We will develop refined model of cholera transmission by including factors recognized from our previous study, incorporating the new variables that prove to be correlated with cholera case, but not yet included in our predictive model.

Using these data we will further refine our model of cholera transmission which will be useful in predicting outbreaks of cholera, thereby facilitate early mobilization of preventive and treatment measures