Outbreak Investigation of African swine fever in a Multi-Farm Pig Cluster at Gudugba, Ewekoro (Ogun State) Nigeria

Abstract

African Swine Fever (ASF) is a highly contagious viral infection of pigs that causes severe losses in pig farming worldwide, with Nigeria among the countries most affected. Frequent outbreaks in the country have been associated with weak biosecurity, unrestricted pig movement, and communal slaughter facilities that facilitate rapid viral dissemination. This study describes the epidemiological and clinical features of a confirmed ASF outbreak in a pig farm cluster settlement in Ogun State. A field investigation was conducted on May 20, 2025, following a report of unusual pig deaths in Zone C of the settlement.  Clinical observations, descriptive epidemiology, and trace-back techniques were used to assess the situation.  The affected farm housed 82 pigs, of which 45 died and 12 were culled through emergency slaughter, this represents an attack rate of 69.5% and a case fatality rate of 78.9%. Observed clinical manifestations included anorexia, abortions, generalized weakness, hemorrhagic skin lesions, and sudden death, features that strongly suggested ASF.  Trace-back assessments revealed that several farms across different zones had experienced similar morbidity and mortality in preceding months without formal reporting. These findings suggest silent transmission of ASF within the settlement, likely facilitated by the communal slaughter slab. Samples submitted to the National Veterinary Research Institute (NVRI), Vom, tested positive for ASF virus by Polymerase Chain Reaction assay. The clinical signs, epidemiological features and laboratory test confirmed an active outbreak and highlighted the urgent need for strengthened surveillance, improved reporting, and enhanced biosecurity within the settlement. This outbreak emphasizes the importance of regulating communal slaughter activities, enforcing movement control, and adopting robust biosecurity protocols to limit the spread of ASF in Nigeria’s pig industry.