Co-variations of Cholera with Climatic and Environmental Parameters in Coastal Regions of Tanzania

Abstract

The bacterium causing cholera, Vibrio cholerae, is essentially a marine organism and its ecological dynamics have been linked to oceanographic conditions and climate. We used autoregressive models with external inputs to identify potential relationships between number of cholera cases in the coastal regions of mainland Tanzania with climatic and environmental indices (maximum air temperature, sea surface temperature, wind speed and chlorophyll a). Results show that between 2004 and 2010 coastal regions of mainland Tanzania with approximately 21% of the total population accounted for approximately 50% of the cases and 40% of the total mortality. Significant co-variations were found between seasonally adjusted cases and coastal ocean chlorophyll a and to some degree sea surface temperature, both lagged by one to four months. Cholera cases in Dar es Salaam were also weakly related to the Indian Ocean Dipole Mode Index lagged by 5 months, suggesting that it may be possible to predict Cholera outbreaks for Dar es Salaam 5 months ahead of time. The results also suggest that the severity of cholera in coastal regions is set by conditions in the ocean and that longer-term environmental and climate parameters may be used to predict cholera outbreaks along the coastal regions.