CLIMATE, OCEANS, AND HUMAN HEALTH: THE ECOLOGY AND EVOLUTION OF CHOLERA

Disease agents do not exist in a vacuum, but rather require appropriate environmental conditions, presence of intermediate hosts or vectors, and, for human pathogens, specific social and economic factors that allow for infection and transmission. Thus, the study of disease dynamics requires interdisciplinary understanding gleaned from microbiology, protozoology, genetics, entomology, ornithology, ecology, hydrology, climatology, and ocean and atmospheric sciences, to name some of those most relevant. The web of connection of these seemingly disparate fields and disciplines is best defined as biocomplexity. Cholera, a devastating disease afflicting predominantly those countries lacking sanitation and safe water distribution systems and the source of which is the aquatic environment, provides an exemplary model for study. It is a disease caused by the bacterium, Vibrio cholerae, the host of which is a zooplankter, the copepod, and the ravages of cholera are influenced by environmental factors, including temperature, tides, salinity, and nutrients. More recently, genomics of the causative agent has further extended understanding of its function and epidemiology. More than 125 isolates of Vibrio cholerae and related Vibrio spp. have been sequenced and their genomes analyzed to determine not only pathogenic properties, but also lateral gene transfer, environmental fitness, and evolution. Predictive models for cholera have been constructed and their application to the Haitian cholera epidemic has been illuminating, with strong evidence for environmental drivers of both distribution of the bacterium in the environment and incidence of cholera in the human population. Monitoring parameters predictive of conditions conducive for cholera outbreaks has been achieved with satellite observing systems. This technology has proven not only useful in cholera epidemics but can be employed effectively for monitoring vector borne diseases, in general.