Spatio-temporal and Ecological Analysis of Brucellosis in North of Iran

Epidemic diseases are a public health concern that has many economic costs and health problems. The geographical distribution of these diseases is a spatial and temporal process. By understanding the process and identifying the factors that affect it, we can take an effective step in preventing and treating these diseases. Brucellosis is one of the most important zoonotic diseases in Iran. To better understand the epidemiology of this disease in northern Iran, the main objectives of this study are to review the annual and monthly trends, to identify spatial and space-time clusters, and to determine the impact of ecological variables. The study was conducted on 6895 patients from April 2009 to March 2017. Data of disease incidence with environmental data including average temperature, maximum temperature, minimum temperature, number of freezing days, humidity, precipitation, evaporation, wind speed, vegetation, elevation, slope and aspect in Golestan, Mazandaran and Gilan provinces as Monthly collected. Global Moran's I was used to investigate spatial autocorrelation. Spatial scan, local moran’s I and space-time scan were used to identify clusters. Spearman correlation was used to study the effect of ecological parameters. The results showed that brucellosis was clustered in northern Iran. The incidence was maximum in the summer (34%) and at least in winter (16%). The months of May, June, July and August were the most susceptible months with a total of 3396 patients. In Local Moran's I, the cities of Minudasht, Kurdkuy, Bandar Ghaz and Galughah were identified as high-high, the cities of Lahijan, Astaneh Ashrafieh and Rasht as low-low and the shaft town was identified as high-low region. In the spatial scan, 10 classes were discovered, most of which were located in Golestan and Mazandaran, and only one was in Gilan. The first and most dangerous classes were in Golestan province. In a space-time scan, 4 classes were identified. The results obtained from the Moran index and spatial scan and space-time scan were confirmed by each other. Spearman showed a positive correlation between incidence of disease with evaporation, aspect, maximum temperature, height and mean temperature, and negative correlation with precipitation, moisture and vegetation. This study shows that in the north of Iran, we see an increase in the incidence of this disease from west to east. Brucellosis is higher in spring and summer in mountainous regions with warm and dry weather. This information can be used for the control strategy used by decision-makers in the field of health.