Modelling the risks of foot-and-mouth disease outbreaks and assessing the effectiveness of vaccination in South Africa

Abstract

Transboundary animal diseases such as foot-and-mouth disease (FMD) have negative socio-economic consequences that include impacts on food security. Vaccination reduces the number of susceptible animals and is one of the most important approaches for FMD control. In South Africa, FMD outbreaks in communal areas cause major livestock and human livelihood concerns; they raise apprehensions about the effectiveness of FMD control measures within the FMD protection areas. This study aimed to inform South Africa’s FMD control policy by identifying the spatial and temporal distributions of FMD outbreaks, modelling the risks of FMDV outbreaks and assessing the effectiveness of vaccination in South Africa. The first study used Cuzick-Edwards tests and Kulldorff scan statistics to detect spatial autocorrelation and spatial-temporal clusters of FMD outbreaks (2005 - 2016). The second study developed a new vaccine matching technique and assessed the vaccine-match of 41 FMD field viruses isolated from southern Africa (1991 - 2015). The third study developed a risk model integrating available risk factor information to identify high-risk areas for FMD outbreak occurrence and subsequent spread. Four high-risk clusters for FMD outbreaks were identified, and the spatial distribution was consistent with contact between domestic animals and wildlife as the main contributor to FMD occurrence. Cattle numbers, cattle movement, location (province), vaccination status and vaccine matching were also important for FMD outbreak occurrences and spread. However, cattle weekly inspections were strongly related to FMD occurrence, which implies effective surveillance and inspection increased the likelihood of FMD detection. The new vaccine matching method provided a feasible and reliable approach that will contribute to the control of FMD in southern Africa. Continued research is necessary to maximize the cost-effectiveness of FMD control in southern Africa.