A risk assessment for the export of fresh beef products after an outbreak of foot and mouth disease in the free zone of South Africa

Abstract

Foot-and-mouth disease has been recognised as one of the most important diseases constraining international trade in animals and animal products. Economic losses due to reduced exports as well as additional costs of implementation of control measures associated with FMD outbreaks in South Africa have been reported. In order to participate in the international market, countries with FMD endemic areas including South Africa must demonstrate that the likelihood of FMD in fresh beef products is negligible. However, the quantitative risk of FMD virus survival in beef and beef products destined for export from the FMD free zone in South Africa has not been done. This study aims to assess the probability of FMD virus surviving in fresh beef products after implementation of the risk reduction measures at different steps along a beef value chain using quantitative risk assessment stochastic modelling. A quantitative risk assessment was conducted throughout the beef value chain using data from previously published studies in Science Direct, Google Scholar, Web of Science, and PubMed. In addition, an expert opinion questionnaire survey was used to collect additional data on the likelihood of FMD in South Africa. A scenario tree was developed and equations for input variables were created. A probability distribution using A Monte Carlo simulation with 100 000 iterations to model the probability of occurrence of the FMD virus at each node. The overall likelihood of FMD virus contamination of fresh beef products was calculated by adding the probabilities at farm, feedlot and abattoir. A sensitivity analysis was used to determine inputs in the value chain that are correlated with the overall FMD likelihood in fresh beef products using correlation coefficients. A correlation coefficient is the quantification of a statistical relationship between two variables. In addition, the impact of changes in the initial prevalence of FMD in the country and the likelihood of an animal been asymptomatic on the overall FMD likelihood in fresh beef products were also assessed. The overall probability of FMD virus contaminating fresh beef products was negligible (2.1×〖10〗^(-9)). The probability of FMD virus circulation in the country (correlation coefficient (r) =0.72) and the inability to diagnose asymptomatic cattle (r=0.59) were strongly correlated with the probability of FMD virus in fresh beef products. Weak correlations were observed between FMD transmission rate (r=0.17), antemortem, inspection (r=0.9), post-mortem inspection (r=0.09) and the probability of FMD virus in fresh beef products. When the initial probability was increased to 3.4× , the likelihood increased to 1.6 ×〖10〗^(-4) .Similarly, increasing the probability of not detecting asymptomatic animal to 0.6 increased the probability of FMD virus in fresh beef products to 5.2×〖10〗^(-9). The likelihood of FMD virus in fresh beef products destined for export from the FMDV free zone was negligible. The initial prevalence of FMD in the country and the asymptomatic status of FMD infected cattle were strongly associated with the probability of the presence of FMD virus in fresh beef products intended for export from the FMD free zone. Therefore, it is important for regulators and farmers to ENSURE that FMD free status is always maintained and that control measures at farms and abattoirs such as biosecurity, vaccination, passive surveillance, and processing must continue in order to maintain the disease-free status of the FMDV free zone. The addition of active surveillance in the FMD free zone could potentially further decrease the likelihood of FMD survival in fresh beef products.