Par le Pr Rita R. Colwell, PhD, DsC
Distinguished University Professor
University of Maryland, College Park
John Hopkins University Bloomberg School of Public Health, Baltimore, USA
During the mid-1980s, satellite sensors were developed to monitor the continents and oceans of Planet Earth for purposes of understanding climate, weather, vegetation, and their seasonal variations. During that period of time, the role of the environment in infectious disease incidence and transmission was investigated, both qualitatively and quantitatively, using those satellite sensors to document seasonality of diseases, initially malaria and cholera, but since extended to Campylobacter, Salmonella, Shigella, and other agents of infectious diseases. This new technology revealed a very tight connection of the environment to many infectious diseases, especially waterborne and/or vector infectious diseases. With satellite sensors, those relationships could be quantified, comparatively analyzed, and even more predictive models developed. More recent studies of epidemics have provided even more powerful models, both retrospective and prospective, for understanding and predicting disease epidemics. Epidemics of the water borne diseases caused by vibrios and aeromonads can be characterized with information from satellite monitoring of temperature, salinity, and chlorophyll, the latter serving as a tag for phytoplankton that seasonally precede zooplankton in abundance in coastal and river waters. Since our studies have shown that components of zooplankton (copepods and cladocerans, predominantly) carry vibrios in their natural flora, data obtained using satellite sensors offer the capacity for predicting epidemics. Recent studies of historical data for India on cholera deaths 1875-1948, coupled with meteorological data stored in archives for India in that time period, provide critical data from which to build a useful model to study the cholera epidemic that erupted in Haiti in 2010, and outbreaks of other vibrio diseases, e.g., Vibrio parahaemolyticus food borne disease and Vibrio vulnificus. As determined from historical data for India, elevated air temperatures for two months preceding a cholera epidemic, coupled with significantly heavier rainfall at the time of onset of the epidemic, and occurrence in a geographic region where sanitation and access to safe drinking water were affected by a disruptive event, e.g., an earthquake, the probability of epidemic cholera , as opposed to endemic cholera, is high. Examples of cholera epidemics in Bangladesh, Zimbabwe, and Haiti, as well as earlier studies on Campylobacter are provided. Based on these studies, an early warning system for a waterborne infectious disease can, indeed, be developed, providing a powerful tool for protecting public health and for measuring effects of climate change on infectious disease agents.
In parallel with environmental studies, genomic analyses of Vibrio species, including V. parahaemolyticus, V. vulnificus, and V. cholerae, provided evidence of multiple sources of the causative agent of epidemics. Furthermore, metagenomic data of clinical samples revealed more than one pathogen, frequently four to ten different pathogens, were present in clinical samples collected from cholera patients.
A new method for identification and quantification of bacteria to species and strains, GENIUS, was employed in metagenomic analysis of clinical samples of these cholera patients, utilizing DNA sequence data. The results indicated the necessity to redefine diarrheal disease causal agents as a community of pathogens, rather than a single agent. In conclusion, with the tools of satellite sensing and environmental modeling, coupled with genomic analyses, the inter-relationships of infectious disease, climate, and human health can be better understood and more effective protective measures developed.
Lundi 23 juin 2014 à 10h30 à l'IPEV (1er étage)