Browse by author
Lookup NU author(s): John Broderick
Full text is not currently available for this publication.
Vibrio cholerae, the aetiological agent of cholera, is an autochthonous component of brackish water ecosystems. Attachment to phytoplankton and zooplankton has been shown to increase survival and growth of the bacterium in mesocosm experiments. As a result, correlations between water temperature, chlorophyll a and outbreaks of the disease have been attributed to a plankton mediated chain of infection. It is hypothesised that nutrient enrichment of brackish waters might result in similar increases in environmental V. cholerae. Water samples were taken from brackish waters on the south coast of Sri Lanka and analysed for soluble nitrate, phosphate, salinity. V. cholerae was detected using a species specific nested polymerase chain reaction (PCR). Nitrate concentration was found to correlate with Secchi depth readings and salinity implying that the hydrodynamic regime is important in regulating the trophic state of each of the water bodies. Comparison with counts of faecal Streptococci taken from a parallel study of the ecosystems suggests soluble nitrates, most likely from agricultural sources, are more significant than wastewater in the eutrophication of the brackish waters sampled. Low levels of V. cholerae were detected and binary logistic analysis could not attribute presence or absence to any other variable or combination of variables. If environmental levels of V. cholerae are independent of phytoplankton abundance and its correlates then relationships between physical environmental variables and incidence of disease may be more likely to be due to direct effects on the bacteria's growth. Tentative recommendations for Sri Lankan coastal management are that V. cholerae are present in the brackish water ecosystems tested are unlikely to pose a public health risk because of their low concentrations. There do not appear to be grounds to manage lagoons for lower productivity as high phytoplankton levels do not appear to predispose a water body to the presence of V. cholerae.
Author(s): Broderick JF
Publication type: Report
Publication status: Published
Series Title:
Year: 2003
Pages: 10
Institution: School of Marine Science and Technology, University of Newcastle Upon Tyne
Place Published: Newcastle Upon Tyne, UK
