Using Earth Observation To Forecast Human and Animal Vector-Borne Disease Outbreaks

Earth observing technologies, including data from with earth-orbiting satellites, coupled with new investigations and a better understanding of the impact of environmental factors on transmission dynamics of mosquito-borne diseases permitted us to forecast Rift Valley fever (RVF) outbreaks in animals and humans months before an outbreak and in time to protect humans and animals. The classification of RVF epidemics or epizootics as natural disasters directly linked to extreme global climate anomalies cannot be overemphasized. The RVF outbreak of 1997-1998 across 5 countries in the Horn of Africa led to over 90,000 human infections, the loss of more than 100,000 domestic animals, and a costly ban on livestock exports, in addition to the economic impacts described above. The use of remotely sensed vegetation measurements, which have now been archived for the last 30 years, combined with other climate data sets such as rainfall and sea surface temperatures have come to play an important role in the study of the ecology of arthropod-borne diseases. We show that epidemics and epizootics of previously unpredictable RVF are directly influenced by large scale flooding associated with the El Niño/Southern Oscillation. This flooding impacts the ecology of disease transmitting mosquito vectors through vegetation development and other bioclimatic factors. Overall, for East Africa the early warning information provided in 2006 enabled country preparedness and early detection and response activities to be undertaken ~2 months earlier compared with the previous epidemic/epizootic of 1997–1998.  Forecasting permitted enhanced control efforts including vaccination of livestock, vector control, and animal quarantines and animal product use restrictions to minimize impacts of the epizootics/epidemics. This information is now utilized to monitor, model, and map areas of potential RVF outbreaks and is used as an early warning system for risk reduction of outbreaks to human and animal health, trade, and associated economic impacts. Global climate also influences local conditions that can affect other emerging vector-borne disease patterns because the pathogens, their vectors, and hosts are sensitive to temperature moisture, and other ambient environmental conditions. In this presentation, in addition to RVF, we also examine linkages between climate, ecosystems and elevated transmission of dengue, chikungunya, and malaria. During periods of elevated transmission there is a significantly increased risk of globalization of these and other diseases. The ability to predict periods of elevated risk permits us to design better prevention, containment, or exclusion strategies to limit globalization of emerging pathogens.