Zonation of Shigellosis and its Relationship With Climatic Factors, Case Study: Chaharmahal and Bakhtiari Province Between 2011 and 2014

Background and aims: Shigellosis or bacillary dysentery is an infectious disease transmitted through water and food. It is a type of infectious colitis caused by Shigella bacteria. The aim of this study is to determine the prevalence and the spatial distribution of shigellosis and its relationship with climatic factors in Chaharmahal and Bakhtiari province. Methods: In this study, population of infected people to shigellosis in the province during 2011 to 2014 obtained from reliable sources and analyzed. The statistics were standardized for every city in the event of illness per hundred thousand people. The relationships between incidence of the disease and the climatic factors (temperature, rainfall and humidity) were investigated by Pearson correlation coefficient after generation of zonation map using GIS and analysis of the concentration centers. Results: According to the results, Koohrang, Lordegan and Ardal cities are classified as high risk areas with an incidence more than 400 000 people. Borujen and Faarsan cities are medium risk areas with an incidence less than 250 per 100 000, and Shahr-e-kord city with an incidence less than 100 per 100 000 people is considered a low risk area. The incidence grows with increase in the temperature. Increase in the precipitation and humidity decreases incidence of the disease. Concentration and prevalence of shigellosis mostly occur in west of the province, because this area is located in the neighborhood of Khuzestan province, and also due to nomadic residence of Bakhtiari nomads in this part during summer and their unhealthy lifestyle, limited access to treated water and especially consumption of untreated surface water. The higher concentration of nomadic residence and higher contamination of water increase incidence of waterborne diseases. The frequency increase of the disease in warm seasons can be due to prevalence of Shigella dysentery in the region. Conclusion: Based on the results, significant positive correlations exist between the surface water consumption, the temperature increase, the number of pisciculture centers in the area and incidence of the disease. Significant negative correlations are also observed between the rainfall, humidity and incidence of the disease.