Pathological and molecular diagnosis of porcine Circovirus 2 in slaughtered pigs of India

Porcine Circovirus 2 (PCV2), an emerging viral pathogen of pigs is distributed worldwide causing huge economic loss to the swine industry. Despite its high prevalence globally, very little or no reports are available regarding the prevalence of porcine circovirus-2 (PCV-2) in slaughtered pigs. The objective of our study was to estimate the prevalence of PCV2 in Indian slaughtered pigs using pathological and molecular techniques. Out of 968 morbid tissue samples (lungs-484; lymph nodes-484) collected from slaughtered pigs showed the high prevalence of PCV2 (65.28%) by PCR targeting ORF2 gene showing the amplification of 481 bp. Among 632 positive morbid tissues, lungs (52.89%) showed higher detection of PCV2 DNA as compared to lymph nodes (12.39%). Microscopically, affected lungs showed the predominant lesions of subacute interstitial pneumonia, proliferative and necrotizing pneumonia with suppurative bronchopneumonia. The lymph nodes showed the predominant lesions of lymphoid depletion with infiltration of histiocytes and macrophages in the medullary cords and sinuses. PCV2 antigen was immunohistochemically demonstrated in the alveolar macrophages and mononuclear cells in the lymph nodes confirming the association of PCV2 with associated pathologies. The phylogenetic analysis revealed that the PCV2 isolates circulating in pigs belonged to PCV2d-2 genotype. In conclusion, this study shows that PCV2d-2 is an emerging genotype circulating in Indian slaughtered pigs, which warrants the immediate implementation of PCV2 vaccination to aid the development of prevention and control strategies.