Abstract
Modelling the spatial distributions of human parasite species is crucial to understanding the environmental determinants of infection as well as for guiding the planning of control programmes. Here, we use ecological niche modelling to map the current potential distribution of the macroparasitic disease, lymphatic filariasis (LF), in Africa, and to estimate how future changes in climate and population could affect its spread and burden across the continent. We used 508 community-specific infection presence data collated from the published literature in conjunction with five predictive environmental/climatic and demographic variables, and a maximum entropy niche modelling method to construct the first ecological niche maps describing potential distribution and burden of LF in Africa. We also ran the best-fit model against climate projections made by the HADCM3 and CCCMA models for 2050 under A2a and B2a scenarios to simulate the likely distribution of LF under future climate and population changes. We predict a broad geographic distribution of LF in Africa extending from the west to the east across the middle region of the continent, with high probabilities of occurrence in the Western Africa compared to large areas of medium probability interspersed with smaller areas of high probability in Central and Eastern Africa and in Madagascar. We uncovered complex relationships between predictor ecological niche variables and the probability of LF occurrence. We show for the first time that predicted climate change and population growth will expand both the range and risk of LF infection (and ultimately disease) in an endemic region. We estimate that populations at risk to LF may range from 543 and 804 million currently, and that this could rise to between 1.65 to 1.86 billion in the future depending on the climate scenario used and thresholds applied to signify infection presence.
Highlights
The role of risk mapping in describing the spatial patterns of infection and guiding the planning of parasite control is wellestablished, and has been demonstrated for a range of major parasitic diseases, including malaria [1,2], trypanosomiasis [3,4], schistosomiasis [5,6], onchocerciasis [7], and lymphatic filariasis [8,9,10]
We evaluated Maxent, a presence-only maximum entropy-based niche modelling technique [41], to describe the ecological requirement and current potential distribution of Lymphatic filariasis (LF) in Africa, and to determine for the first time how future climate change may affect the distribution and burden of this disease on the continent so that better prevention and control efforts could be directed to mitigate against the effects of such change
The relative importance and contribution of the original ten environmental, altitude and population density variables to the initially selected three niche models of LF occurrence, assessed by considering the percentage contribution that each variable made to the total test gain and by using a jackknife procedure to determine which of these variables caused the biggest lost in model AUC when each was excluded one at a time, resulted in the selection of the following five variables: population density, mean maximum temperature, mean temperature in the coldest month, mean annual precipitation and altitude
Summary
The role of risk mapping in describing the spatial patterns of infection and guiding the planning of parasite control is wellestablished, and has been demonstrated for a range of major parasitic diseases, including malaria [1,2], trypanosomiasis [3,4], schistosomiasis [5,6], onchocerciasis [7], and lymphatic filariasis [8,9,10]. Following the conclusion by an independent International Task Force for Disease Eradication that lymphatic filariasis may be one of only six infectious diseases that can be considered to be ‘‘eradicable’’ or ‘‘potentially eradicable’’ [18], the World Health Assembly in 1997 adopted Resolution WHA50.29 calling for the elimination of LF as a public health problem globally
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
