Pathological investigation and viral antigen distribution of postweaning multisystemic wasting syndrome in association with porcine parvovirus infection of pigs in Kerala, Southern India

Postweaning multisystemic wasting syndrome (PMWS) is one of the important emerging porcine circoviral associated disease (PCVAD) causing immense economic losses throughout the world producing mortality and morbidity mainly in post-weaned pigs. During the period from 2018-2019, a total of 50 pig carcasses from different parts of Kerala were screened for concurrent infections of porcine parvovirus (PPV) and porcine circovirus type 2 (PCV2), followed by the establishment of PMWS. All the samples were subjected to polymerase chain reaction (PCR) initially followed by histopathology and immunohistochemistry (IHC). Phylogenetic analysis was performed for PPV using non-structural gene -1(NS1). The result of the molecular screening using polymerase chain reaction revealed only one sample to be positive for both PCV2 and PPV. The gross lesions noted were the non-collapsed voluminous lungs, necrotising lymphadenitis, interstitial nephritis, splenomegaly and fibrinous pericarditis. Histopathological examination revealed mild interstitial pneumonia, lymphoid depletion in periarteriolar lymphoid sheaths of spleen with focal areas of granulomatous inflammation, depletion of the germinal centre of the follicles in the lymph nodes, non-suppurative myocarditis and interstitial nephritis. Further, immunohistochemistry demonstrated PCV2 and PPV antigens in the affected tissues. Based on the clinical signs, histopathological lesions and immunohistochemical demonstration of PCV2 antigen, the case was confirmed as PMWS in association with PPV. This report of PMWS in association with PPV confirms, probably for the first time in the Kerala state of India.