First Evidence of Porcine Epidemic Diarrhoea Virus and African Swine Fever Virus Natural Co-Infection in Pigs from Karnataka, India: An Epidemiological Investigation

This study reports a diarrhoeal outbreak in pigs primarily caused by Porcine Epidemic Diarrhoea Virus (PEDV), with co-infection of African Swine Fever Virus (ASFV)-a first evidence of natural PEDV-ASFV co-infection in India with outbreak implications. Distinct clinical signs were observed: majority of pigs exhibited profuse yellow watery diarrhoea and vomiting typical of PED, while a few showed high fever, systemic haemorrhages, and coffee-coloured diarrhoea indicative of ASF. The outbreak lasted 25 days and followed a propagated epidemic curve, suggesting pig-to-pig transmission. Epidemiological investigation implicated farm labourers returning from an ASF and PEDV-affected premise in disease introduction. Using case definitions, snowball sampling enabled tracing of five additional affected farms spread across two districts, demonstrating its utility in outbreak mapping under limited cooperation settings. Molecular testing confirmed PEDV and ASFV in sampled pigs from the investigated farm. The presence of PEDV in faecal samples was confirmed using the fluorescent antibody test (FAT) on Vero cell monolayers. Phylogenetic analysis placed PEDV isolates within the G2a genotype, closely related to previously detected Indian strains along with Chinese and South Korean strains, while ASFV aligned with Genotype II, consistent with Indian and East Asian lineages. This co-infection highlights the diagnostic complexity of pig diarrhoeal outbreaks and underscores the need for integrated surveillance and stricter biosecurity.