Analysis of the drivers of ASF introduction into the officially approved pig compartments in South Africa and implications for the revision of biosecurity standards

Background: While African Swine Fever (ASF) virus has historically circulated in wild pigs and in Ornithodoros ticks in parts of South Africa, the virus has spread among domestic pigs throughout the country since 2019. South Africa's compartment system has been used as a mainstay approach to protecting the swine industry in the face of ASF. However, in 2020, two compartments broke down with ASF. The objectives of this study are to investigate the drivers for ASF introduction into the compartments, to categorize compartments by risk of ASF introduction, and to make corresponding recommendations. The relevance of risk factors for ASF introduction for each compartment were investigated among veterinarians and farm managers. The analysis of risk factors weighted according to an expert elicitation were used to categorize compartments into risk levels. Results: Drivers of disease related to human behaviors and to domestic pig management are perceived by farm managers and veterinarians of the compartments to be critical for ASF introduction into compartments in South Africa. Twenty-four units were categorized as high risk, forty-seven as medium risk, and twenty-four as low risk. "Insufficient boot and clothing biosecurity by animal health personnel" was identified as a relevant risk factor in all high risk units. Other prominent risk factors were "insufficient boot and clothing biosecurity by external people," "underreporting of suspect ASF cases," "improper hunting/ culling of wild suids inside the compartment," "un-tested introductions into the herd," and "entry and contact with free-roaming pigs." The roles of wild pigs and competent vectors are considered minimal. There is a need for revision of the compartment standards and training of compartment personnel on the standards. The major gaps identified in the standards were absence of a monitoring programme to assess biosecurity implementation and suboptimal surveillance testing and audit strategies. Conclusions: The results of our study confirm that ASF is increasingly an anthropogenic problem. Updating the compartment standards and addressing gaps in the knowledge of compartment personnel on ASF are most critical. To enhance compliance with biosecurity measures and thus control the disease, close engagement with all stakeholders linked to the compartments is needed.