Risk Mapping of Visceral Leishmaniasis: The Role of Local Variation in Rainfall and Altitude on the Presence and Incidence of Kala-Azar in Eastern Sudan

Abstract

Visceral leishmaniasis (VL) is a vector-borne disease highly influenced by environmental factors. A model was developed for mapping the distribution and incidence of VL in Gedaref State, eastern Sudan, in relation to different environmental factors. Geographical information systems (GIS) were used to extract and map regression results for environmental variables of 190 villages in Gedaref State, including rainfall, vegetation status, soil type, altitude, distance from river, topography, wetness indexes, and average rainfall estimates. VL incidence in each village was calculated from hospital records. By use of logistic and linear multivariate regression analyses, models were developed to determine which environmental factors explain variability in VL presence and incidence. We found that average rainfall and the altitude were the best predictors of VL incidence. The resulting models were mapped by GIS software predicting both VL presence or absence and incidence at any locality in Gedaref State. The results are discussed in relation to VL control.

Identification of environmental parameters and risk mapping of visceral leishmaniasis in Ethiopia by using geographical information systems and a statistical approach

“…In the current study, the annual average temperature shows a high leverage on VL occurrence (33%), which is in line with a previous study done in Gedaref State in Sudan by Elnaiem (2003). Soil was found to be the second most important determinant with a percentage influence of 27%.…”

“…According to FAO data, vertisol has a high content of the expanding clay type known as montmorillonite that forms cracks when dried but which absorbs water and swells causing self-mulching during the rainy season. The deep cracks provide a sand fly microhabitat suitable for breeding and resting (Elnaiem, 2003). This soil type is found associated with the red acacia and P. orientalis, which are common in areas endemic for L. donovani transmission (Gebre-Michael et al, 2010).…”

“…The range of 1,794-1,872 m was found to be the second most favourable category for VL in this study. The Elnaiem et al (2003) study in Gedaref state of Sudan, using a probabilistic model, concluded that altitude is one of the best predictors for the presence of VL in a village. The long-known endemic foci established through epidemiological surveys and self-reported cases of VL in Ethiopia are from the lowlands and the recently reported highland foci range from 1,800 to 2,000 m (Ali et al, 1994;Hailu et al, 1996;Alvar et al, 2007;Herrero et al, 2009;Sordo et al, 2012).…”

Environmental modelling of visceral leishmaniasis by susceptibility-mapping using neural networks: a case study in north-western Iran

“…Geographical information systems (GIS) can be applied for risk mapping and identifying endemic areas for diseases (Elnaiem et al, 2003;Rinaldi et al, 2006;Pezeshki et al, 2012). For example, Bhunia et al (2011) studied the influence of the distribution of inland water bodies on transmission of VL and presence of its dominant vector in a GIS model.…”

Localization of kala-azar in the endemic region of Bihar, India based on land use/land cover assessment at different scales

“…Posteriori risk modelling for kala-azar in Africa and Asia suggests that rainfall, altitude and cultivation patterns can predict the transmission rates (Elnaiem et al, 2003;Sudhakar et al, 2006;Bhunia et al, 2010a). Landscape variables such as land use/land cover (LULC) may be particularly important since they are directly linked to vector presence (Feliciangeli et al, 2006).…”