Monday, 10 January 2005: 2:00 PM
Climate Factors Affecting Human Health in Coastal Regions
An environmental source of cholera was hypothesized as early as the late nineteenth century by Robert Koch, but not proven because of the inability to isolate Vibrio cholerae, the causative agent of cholera, from the environment between epidemics. Standard bacteriological procedures for isolation of vibrios from environmental samples, including water, between epidemics generally were unsuccessful because Vibrio cholerae, a marine vibrio, requiring salt for growth, enters into a dormant, "viable but nonculturable stage," when conditions are unfavorable for growth and reproduction. Recently, an association of Vibrio cholerae with zooplankton, notably copepods, has been established. Furthermore, the sporadicity and erraticity of cholera epidemics have now been correlated also with climate and climate events, such as El Niņo. Since zooplankton have been shown to harbor the bacterium and zooplankton blooms follow phytoplankton blooms, remote sensing can be employed to determine the relationship of cholera epidemics with sea surface temperature (SST), sea surface height (SSH), chlorophyll, and turbidity. Cholera occurs seasonally in Bangladesh, with two annual peaks in the number of cases. From clinical data and data obtained from remote sensing, it has been found that when the height of the ocean is high and sea surface temperature is also elevated, cholera cases are most numerous. When the height is low and the sea surface temperature also low, little or no cholera occurs. Because SST, SSH, and blooms of plankton have been significantly correlated with cholera epidemics, selected climatological factors and incidence of V. cholerae can be recorded, and prediction of cholera epidemics is now possible. Simple filtration interventions have proven successful, based on the association of V. cholerae with plankton. They are a simple, although transient, solution to the age-old problem of controlling this waterborne disease.