Toward Early Warning and Early Action in Sudan: Public Health and the Environment

By Sudan Health and Air Quality Team , posted on November 17th, 2013 in DEVELOP Fall 2013 VPS

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Team Location: International Research Institute for Climate and Society, Palisades, New York

Kala Azar reporting sites in Gedaref State, Sudan, with overlay of average minimum land surface temperature (LST) from April 23-30, 2010, using the data set from the MODIS sensor aboard the NASA Aqua satellite. Image Credit: Sudan Health and Air Quality Team, NASA DEVELOP National Program

Kala Azar reporting sites in Gedaref State, Sudan, with overlay of average minimum land surface temperature (LST) from April 23-30, 2010, using the data set from the MODIS sensor aboard the NASA Aqua satellite. Image Credit: Sudan Health and Air Quality Team, NASA DEVELOP National Program

Authors:
Alex Sweeney (Columbia University), Project Lead
Andrew Kruczkiewicz (Columbia University)

Mentors/Advisers:
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)

Past/Other Contributors:
Dia Elnaiem, Ph.D. (University of Maryland – Eastern Shore)
Omran F. Osman, Ph.D. (Federal Ministry of Health and the University of Khartoum, Sudan)
Doctors without Borders, Switzerland and the Netherlands

Abstract:
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.

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4 comments
anjward7
anjward7

This is really important work.   I hope soon we can understand better and find a way to relieve endemic regions soon.Did you all come across anything in the literature that described vector control as a way of fighting this disease?

 

andrewkruczkiewicz
andrewkruczkiewicz

@anjward7 Hi! Yes, we have read about possible ways to control the vector, but through our research and conversations with partners in the field we find that we are not at that stage yet. There is still work to be done to understand the relationship between climate and the vector. NASA satellite data and new advancements in remote sensing technology are making that possible in an exciting way!

anjward7
anjward7

@andrewkruczkiewicz  Thanks!  When vector control is ready, remotely sensed data products will continue to help target areas where resources should be disbursed.  What other future work was turned up as a result of your study? 

andrewkruczkiewicz
andrewkruczkiewicz

@anjward7 Hi, Glad to see you are interested! Future work include high resolution monitoring of water bodies, understanding the flooding patterns of the nearby Nile River, analyzing the relationship between flora and sandfly development and conversing with local authorities to understand the non-climatic socioeconomic drivers of the disease.

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