Epidemiology and genotype characterization of African swine fever virus of the first confirmed outbreak in Bangladesh

A field and laboratory investigation was conducted to characterize the epidemiology of first confirmed outbreak of African swine fever (ASF) along with identification and molecular characterization of the causative virus in a state-run Pig Development Farm in Rangamati district of Bangladesh. Clinical and post-mortem examinations were performed coupled with real-time PCR and phylogenetic analyses targeting the B646L (p72), E183L (p54), and B602L (CVR) genes. Transmission dynamics were assessed using a Susceptible–Infected–Removed (SIR) model, and the basic reproduction number (R₀) was estimated from contact, transmission, and infectious period parameters. The outbreak affected a closed population of 434 pigs and resulted in 100% morbidity and mortality within four weeks. Affected pigs exhibited high fever, anorexia, erythema, respiratory distress, epistaxis, and sudden death, with post-mortem findings including splenomegaly, hemorrhagic lymph nodes, and hepatic necrosis. Phylogenetic analysis identified genotype II ASFV closely related to strains circulating in South and East Asia and Europe, indicating transregional dissemination. The epidemic curve suggested a point-source outbreak with an estimated R₀ of 3.70 and peak infection within nine days. These findings highlight the urgent need for strengthened surveillance, improved biosecurity, and targeted epidemiological studies among pig population in Bangladesh.