Natural co-infection of pigs with African swine fever virus and porcine reproductive and respiratory syndrome virus in India

Porcine reproductive and respiratory syndrome (PRRS) and African swine fever (ASF) are economically important diseases of pigs throughout the world. During an outbreak, all age groups of animals except piglets < 1 month of age were affected with symptoms of high fever, cutaneous hemorrhages, vomition with blood, diarrhea, poor appetite, ataxia, and death. The outbreak was confirmed by the detection of the N gene of the porcine reproductive and respiratory syndrome virus (PRRSV) and the VP72 gene of the African swine fever virus (ASFV) by PCR in representative blood samples from affected pigs followed by Sanger sequencing. Mixed infection was also confirmed by simultaneous detection of both the viruses using multiplex PCR. Phylogenetic analysis of both the viruses revealed that the outbreak was related to ASFV and PRRSV strains from China which were also closely related to the PRRSV and ASFV strains from the recent outbreak from India. The study confirmed the involvement of genotype II of ASFV and genotype 2 of PRRSV in the present outbreak. Interestingly, PRRSV associated with the present outbreak was characterized as a highly pathogenic PRRSV. Therefore, the present study indicates the possibility of future waves or further outbreaks of these diseases (PRRS and ASF) in this region. This is the first report of ASFV and PRRSV co-infection in pigs from India.