Pathology and Molecular Diagnosis of Respiratory Disease Outbreak due to PCV-2 in a Pig Farm in Goa, India

Background: Pig farming is an important source of income and nutrition for rural farmers in Goa. Pig production is threatened by many infectious diseases. The present study reports a respiratory disease outbreak in a total of 200 pigs including adults and piglets with 40% mortality in a pig herd of Large white Yorkshire and crossbreds in South Goa during the winter period in January 2022. Method: The farm was visited and recorded clinical signs and post mortem findings and and samples were collected for bacterial isolation, PCR confirmation of bacterial and viral pathogens and histopathology. Result: The affected pigs showed high fever, reduced feed intake, staggering gate, huddling, difficulty in breathing, cough, and brown to greenish diarrhea followed by death within a span of 3 weeks. Major gross lesions were non-collapsed lungs with severe congestion and localized areas of consolidation, severe congestion of viscera, and enlargement, and presence of multifocal areas of necrosis in the liver. Histopathology of lungs focal or diffuse bronchointerstitial pneumonia and the lymphoid organs showed lymphoid depletion. Pasteruella multocida could be isolated from heart blood and tissues from 3 cases and PCR of the tissue DNA confirmed the presence of P. multocida and Porcine Circo Virus-2 (PCV-2) infection. The study confirms the presence of PCV-2 infection in pig herds in Goa for the first time. The acute mortality can be attributed to the co-infection of the herd with PCV-2 and P. multocida and sudden change in weather patterns with prevailing severe cold conditions during time of outbreak. Sequencing and Phylogenetic analysis of the PCV-2 ORF-2gene showed the PCV-2 virus from Goa is more related to isolates from southern Indian states.