Field events, clinical findings, and biosecurity breaches in the African swine fever outbreak in Southwest Nigeria (2019-2021).

Background: African swine fever (ASF), a highly contagious, hemorrhagic viral disease of pigs, continues to decimate the global pig population. Aim: This study was designed to investigate key field events, morbidity patterns, mortality rate, clinical findings in pigs, and biosecurity breaches on farms during the ASF outbreak in Southwest Nigeria (2019-2021) Methods: Farms ( Results: Most of the farmers were between 40 and 60 years old and were predominantly men. A significant proportion had over 5 years of experience, and most had a pre-outbreak herd of 200 pigs or less. Many farmers had experienced previous ASF outbreaks leading to losses. Pig age was associated with the sequence of morbidity onset, with the most frequent sequence being adults → piglets → weaners → growers. Mortality, farm size reduction, and financial loss were 60.6%, 92.1%, and ₦166,264,000, respectively. Clinical findings were consistent with hemorrhagic fever in pigs. Biosecurity breaches include a lack of quarantine facilities, limited use of fencing, gating, foot dips, and netting, pig farm aggregation, continuous pig flow on farms, poor vehicle disinfection, uncertified replacement stock, open waste dumping, uncontrolled visitor access, and unrestricted pig movement. Conclusion: Biosecurity breaches across farm infrastructure, management practices, and human behavior aided the spread of ASF in Nigeria, leading to significant economic losses. Strengthening biosecurity, regulating pig movement and market activities, educating stakeholders, and ensuring government led surveillance and compensation are critical to controlling ASF and safeguarding Nigeria's pig industry.