Team Location: International Research Institute for Climate and Society, Palisades, New York
Alex Sweeney (Columbia University), Project Lead
Andrew Kruczkiewicz (Columbia University)
Pietro Ceccato, Ph.D. (International Research Institute for Climate and Society, Columbia University)
Madeleine Thomson, Ph.D. (International Research Institute for Climate and Society, Columbia University)
Dia Elnaiem, Ph.D. (University of Maryland ÛÒ Eastern Shore)
Omran F. Osman, Ph.D. (Federal Ministry of Health and the University of Khartoum, Sudan)
Doctors without Borders, Switzerland and the Netherlands
Visceral Leishmaniasis (VL), also known as kala azar, is a disease caused by the parasitic protozoa, Leishmania donovani. It is transmitted by the bite of a female sandfly of the genus Phlebotomus. Regions endemic to this disease exist within Eastern Africa with geographic hotspots in Sudan and South Sudan. In the past 30 years, outbreaks have occurred cyclically within these two countries, but recent shifts in endemicity have necessitated a more robust understanding of the drivers of the disease.
Research has found that there may be a relationship between environmental factors and the spread of VL. Unfortunately, this relationship is complex since the vector, the vector’s environment and the human population exhibit unique sensitivities to the environment.
In order to understand transmission, it is necessary to understand the climatic factors associated with VL and its ecological boundaries (Quate, 1964). No concerted effort, until now, has been undertaken to understand how leishmaniasis cases are associated with climate variables on a year-to-year basis, and whether there is a significant association with wet or dry years (Ashford & Thomson, 1991). This project examined temperature, precipitation, normalized difference vegetation index (NDVI) and relative humidity. In addition, we looked at environmental factors associated with the habitat of Phlebotomus orienatlis. These include the presence of water bodies, vertisols (specifically black cotton soils), and forests predominated by Acacia and Balanites trees (Elnaiem, 2011).
To account for the influence of climatic variables on VL, cluster and time series analyses were performed using remotely sensed products over the study period of 1996-2012. To account for the effect of water bodies on VL, the NASA Jet Propulsion Laboratory Inundated Fraction product was used. The higher-resolution Landsat data was then used to validate and downscale this product. Earth observation data were obtained primarily from NASA Earth satellites, such as Landsat, Aqua, Terra, Tropical Rainfall Measuring Mission (TRMM), QuikSCAT (Quick Scatterometer) and ALOS (Advanced Land Observation Satellite). Epidemiological data were obtained from the University of Maryland Eastern Shore, provided by Dr. Dia Elnaiem and Doctors without Borders from Switzerland and the Netherlands.
Results of this study suggest that the climate state during the months of March, April, May, and June (MAMJ) can predict conditions for P. orientalis. Examining the environmental parameters during the height of sand fly activity, it was found that lack of vegetation, a delay in the start of the rainy season, and lower inundation levels in May are conducive to increasing the risk of VL transmission. The results from this study imply that a Leishmaniasis Early Warning System can be developed based on climate variables, much like those that have been established for malaria.