Spatio-temporal patterns of anthrax outbreaks in cattle in Kween and Arua Districts, Uganda

Abstract

A study was done to understand and compare the spatiotemporal patterns of cattle anthrax outbreaks with emphasis on progression, intensity, direction, and hotspot areas in Arua and Kween districts. Data were collected retrospectively from four organizations. Site visits were also carried out during an active outbreak to collect more data. Spatiotemporal patterns of two endemic areas located at different altitudes with 308 cases in Kween and 379 in Arua districts were analyzed using ArcGIS, saTscan, and ClusterSeer. The results showed seasonality was comparable between the sites with peaks in May in Arua and June in Kween districts. Cattle anthrax cases were distributed along water bodies with significant positive correlations between cases and at risk cattle populations in Kween (P = 0.01, r2= 0.3) and Arua (P = 0.0001, r2= 0.622) districts. Disease hotspots were observed in both districts with spatially overlapping dates. Significant spatiotemporal clustering occurred in both districts pointing towards a defined source. Significant directional epidemic progression was detected along a water flow gradient of 117.9 degrees in Kween district. In Arua district, whereas the outbreak was spreading with a water gradient of 59.1 degrees, it was more widespread suggesting alternative transmission mechanisms. These findings suggest the spatiotemporal patterns in two endemic regions were site-specific. It was recommended that communal grazing, vaccination coverage, forces of water flow, locations of disease hot spots, and the extents of climatic, environmental, agricultural, and demographic characteristics over space and time should be considered when planning strategies for the prevention and control of anthrax in these endemic settings.