Identification of climatic and environmental factors associated with incidence of cutaneous leishmaniasis in Central Iran using satellite imagery

ABSTRACT

Objective: To determine the effect of climatic and environmental factors on the incidence of cutaneous leishmaniasis in Qom province in 2018. Methods: In this cross-sectional study, the data on cutaneous leishmaniasis incidence were collected from the Disease Control and Prevention Center in Qom province. Climatic and environmental data including Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), and soil moisture were extracted using satellite images. Data of altitude and sunny hours were provided based on shuttle radar topography mission digital elevation model and hemispherical viewshed algorithm, respectively. The associations of climatic and environmental variables with the incidence of the disease were analyzed by Pearson correlation method. The ArcGIS 10.3 software was used to determine the geographical distribution of these factors. Results: There were positive correlations between cutaneous leishmaniasis incidence and the two climatic factors: LST and sunny hours per day (P=0.041, P=0.016), and it had weak negative correlations with the digital elevation model (P=0.27), soil moisture (P=0.54), and NDVI (P=0.62). The time delay analysis showed that in one-, two-, and three month periods, the correlations increased with a 95% confidence interval. Accordingly, the correlation with the three-month time delay was positive and relatively strong between the cutaneous leishmaniasis incidence and LST and sunny hours (P=0.027, P=0.02); nevertheless, there were negative correlations between the cutaneous leishmaniasis incidence and the soil moisture (P=0.27) and NDVI (P=0.62). Conclusions: As Qom is located in one of the semi-arid climate zones, topography and solar energy are important factors affecting the incidence of cutaneous leishmaniasis in autumn. Therefore, appropriate disease control programs are recommended.