Role of estuarine biogeochemistry on abundance and types of Vibrio cholerae in West Bengal: seasonality and relation with cholera incidence
Final Report Abstract
Main goal of this project was to investigate the role of estuarine biogeochemistry on abundance and types of Vibrio cholerae in West Bengal, its seasonality and relation with cholera incidence. During one-year, synchronous sampling campaigns were carried out at two sites at the Hoogly River, a main distributary of the Ganges and also in the Matla mangrove estuarine region The planned work should capture the natural and anthropogenic drivers of Vibrio abundance on a seasonal basis, implying the sampling during one year at two different locations with high and low anthropogenic input. The first comprised a low salinity urban setting in Kolkata (HB), the other a rural, brackish milieu at Diamond Harbour (DH). Driving forces on biogeochemical parameters from intra-day to year round variations of hydrological and climatic changes were studied. It was found that not only anthropogenic input but mainly hydrological variables such as salinity, turbidity, tidal range, temperature and monsoonal precipitation controlled the abundance of cultivable Vibrio, including pathogenic V. cholerae and V. parahaemolyticus. During monsoon, total bacteria and cultivable vibrios (CVC) increased by orders of magnitude at both sites, following elevated river discharge and higher washout of anthropogenic input. The latter was higher in Kolkata, leading to constantly higher abundance of coliforms, especially fecal coliforms and Escherichia coli. Noteworthy, turbidity dependence of CVC was observed particularly at Diamond Harbour, where CVC in intertidal surface sediments and waters followed analogous trends, suggesting bentho-pelagic coupling of Vibrio dynamics. Vibriophages also regulated the occurrence of V. cholera O1 and there was a clear interplay between seasonal variation of V. cholera O1 and its phage O1 Φ in the Hoogly River and cholera incidence in Kolkata. There was a high prevalence of toxin producing enteropathogenic Vibrios among estuarine crabs in the Matla region. CVC was highest from external chitinaceous shell (mean 7 x 107 CFU/gm) of crabs, followed by gut (mean 4 x 106 CFU/gm) and gills (mean 4 x 106 CFU/gm) respectively, reflecting the affinity of Vibrio sp. towards chitinous substrates as an attachment enhancing factor. In riverineestuarine water samples, CVC ranged between 1 and 880 CFU/mL. In comparison CVC among sediment samples ranged between 200 and 600 CFU/gm; increasing substantially in winter months to a range of 800 - 2000 CFU/gm. Considerably higher isolation of toxin producing V. cholerae O1 and V. parahaemolyticus from estuarine crabs indicate that crab plays the dual role of both concomitant transmission and transformation of Vibrios from non-toxigenic to toxigenic progeny. Due to the relevance of these findings for coastal management and human health in tropical regions, it is intended to expand the conducted studies to the aquaculture, socio-economic and public health realms in the Bay of Bengal through the follow-up project “One health: Aquaculture-related pathogen and disease emergence in tropical coastal zones (Bay of Bengal)”, which will participate in the Leibniz Competition 2016.
Publications
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2014. Influence of hydrologic and anthropogenic factors on the abundance variability of enteropathogens in the Ganges estuary, a cholera endemic region. Science of the Total Environment 472: 154-161
Batabyal, P., Einsporn, M.H., Mookerjee, S., Palit, A., Neogi, S.B., Nair, G.B., Lara, R.J.
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2011. Biogeochemical controls on the bacterial population in the eastern Atlantic Ocean. Biogeosciences, Special Issue: Molecular biogeochemical provinces in the eastern Atlantic Ocean. Biogeosciences 8: 3747–3759
Neogi, S.B., Koch, B.P., Schmitt-Kopplin, P., Pohl, C., Kattner, G., Yamasaki, S., Lara, R.J.
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2012. Occurrence and distribution of plankton-associated and free-living toxigenic Vibrio cholerae in a tropical estuary of a cholera endemic zone. Special Edition on “Wetlands and Human Health” Wetlands, Ecology and Management 20(3): 271-285
Neogi, S.B., Islam, M.I., Nair, G.B., Yamasaki, S., Lara, R.J.
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2014. High prevalence of toxin producing enteropathogenic vibrios among estuarine crab in Ganges delta of West Bengal, India. Infection, Genetics and Evolution 26: 359-361
Batabyal, P., Mookerjee, S., Einsporn, M.H., Lara, R.J., Palit, A.
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2014. Seasonal dynamics of Vibrio cholerae and its phages in riverine ecosystem of Gangetic West Bengal: cholera paradigm Environmental Monitoring and Assessment 186:6241-6250
Mookerjee S., Jaiswal A., Batabyal P, Einsporn M., Lara, R. J., Sarkar B.L., Neogi, B.S., Palit, A.
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2014. The role of wetland microinvertebrates in spreading human diseases. Wetlands Ecology and Management.
Neogi, S.B., Yamasaki, S., Alam, M., Lara, R.J.
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Influence of hydrologic and anthropogenic factors on the abundance variability of enteropathogens in the Ganges estuary, a cholera endemic region. Science of The Total Environment, Volume 472, 15 February 2014, Pages 154-161
Einsporn, M.H., Palit, A., Neogi, S.B, Batabyal, P., Mookerjee, S., Nair, S.G., Lara, R.J.
