Mapping as a Tool for Predicting the Risk of Anthrax Outbreaks in Northern Region of Ghana

Abstract

Introduction: Livestock production in northern Ghana is vital in the food security and economic development of the people. The development of this sector is hindered by preventable livestock diseases. Outbreaks of Anthrax and other diseases of public health importance have been reported in Northern Region and have become endemic. To date, no comprehensive study has been conducted to know the risk of Anthrax Outbreaks in the region and the region continues to experience persistent unpredictable outbreaks. The aim of this study was to provide predictive maps to assess the association between soil pH, temperature, rainfall and Anthrax outbreaks. Methods: A descriptive study was conducted with 10-years secondary data using ArcGIS 10.2 to create climate-based risk maps of the area using soil pH, temperature and rainfall as predictor variables. The monthly mean values of rainfall, temperature for ten years were calculated. The mean values and soil pH in each district were concentrated in the centroid of the district. The values were interpolated using the Kriging method to get values within the entire region. Evidence based constant raster values were created as weights for the three factors. The product of the soil pH and its weight was added to the product of the rainfall and its weight to create the soil pH and rainfall predictive map. The soil pH and rainfall predictive map finally added to the product of the temperature and its weight to get the final predictive map. Results: Within 10-years period, there were 43 outbreaks confirmed. The deaths involved were 131 cattle, 44 sheep, 15 goats, 562 pigs with 5 human deaths and 22 developed cutaneous anthrax. The highest number of outbreaks occurred in Zabzugu- University of Ghana http://ugspace.ug.edu.gh v Tatale (5), Yendi (5) and Savelugu-Nanton(5), seasonally, the dry season has the highest 56% and the highest of 9 outbreaks occurred in the month of April. There was a well delineated distribution pattern and the regional predictive map was divided into three strata. Strata I which is the high risk/ hot spot area is made up of East Mamprusi, Bunkpurugu-Yunyoo, Gushiegu, Karaga, Yendi, Saboba-Chereponi, Yendi, Tamale Municipal, Nanumba North and South , East Gonja, and Zabzugu-Tatale districts. Strata II is made up of West Mamprusi, Tolon Kumbungu, Savelugu-Nanton, Kpandai and Sawla/Tuna/Kalba districts and Strata III is made up of West Gonja, Central Gonja and Bole districts. The likelihood of outbreaks occurrence and reoccurrence is higher in Strata I, Strata II and strata III respectively in descending order, due to the suitability of soil pH, temperature and rainfall as well as floods for the survival and dispersal of B. anthracis spore. Conclusion: Spatial risk mapping of Anthrax outbreaks and distribution can help the policy makers develop a risk based surveillance system and focus on areas with high risk and develop strategies of mitigating Anthrax outbreaks and reoccurrence. Keywords: Anthrax, Spatial risk mapping, Northern Region, Soil pH, Temperature, Rainfall.