Spatial correlations of population and ecological factors with distribution of visceral leishmaniasis cases in southwestern Iran.

BACKGROUND & OBJECTIVES Leishmaniasis as a dynamic disease may be markedly influenced by demographic and ecological factors. A geospatial information system study was developed to determine the distribution of visceral leishmaniasis (VL) cases in relation to population, climatic and environmental factors in Fars province, southwest of Iran. METHODS The dwelling addresses of 217 VL patients were obtained from hospital files. A hazard map produced by unifying buffers (5 km) around nomads travel routes (NTR) was developed to survey the effect of close proximity to NTR on the distribution of VL. Mean annual rainfall (MAR), mean annual temperature (MAT), four months temperature mean (T4), elevation, slope and landcover were climatic and environmental factors that have been analysed. Finally, data of dwelling foci were extracted from maps and analysed using logistic regression models. RESULTS Close proximity to NTR was the most important factor influenced on the disease distribution. Climatic factors were in second rank. Among them, temperature especially T4 is the most effective variable and rainfall was also shown to be another effective climatic agent. Most cases of VL were reported from temperate and semiarid areas in western and central regions while arid condition was a confined factor. The environmental factor of landcovers including urban, dry farm and thin forest regions was revealed as the third rank effective factor. Altitude importance was only shown when its effect was studied independently from other factors. INTERPRETATION & CONCLUSION These findings present the distribution of VL in Fars province is influenced by combination of ecological and nomads demographical variables although closeness to NTR and nomads role in distribution and continuance of kala-azar are the most important factors.