The Granger causality analysis of the impact of climatic factors on visceral leishmaniasis in northwestern Iran in 1995–2019

Visceral leishmaniasis (VL) as a vector-borne disease, is an endemic in the northwest and south of Iran and sporadic in other areas in the country. This study was performed to investigate the Granger causality analysis of the impacts of climatic factors on VL in northwestern Iran throughout the period from 1995 to 2019. In a longitudinal study, the epidemiological data of patients suffering from VL were collected from the health centers and hospitals in Meshkinshahr County, Ardabil province, between 1995 and 2019. Moreover, the environmental and climatic data of each location, such as temperature, humidity, rainfall, the number of frost and warm days in the year, were obtained from the meteorological center of the county and put into the Excel software. The incidence rate of VL was modeled by time series analysis and to compare its relationship with other time series covariates, the Granger causality analysis was used. The results of Granger causality analysis showed that some climatic variables including daily mean temperature, absolute minimum temperature, maximum and minimum temperature and maximum humidity were the main factors affecting the prevalence of VL in northwestern Iran. The findings greatly demonstrated that the potential of Granger causality in epidemiologic status of VL in northwestern Iran. Moreover, the results suggest that in addition to patient-related and biological factors, environmental and climatic factors such as temperature and humidity also play a major role in completing the transmittance cycle of VL in an endemic focus.