Mycoplasma hyopneumoniae - a neglected disease as a cause of fibrinous pericarditis in weaned piglets: An etio-pathological assessment

Abstract Fibrinous pericarditis, predominantly of bacterial origin, is frequently documented in slaughtered pigs causing great economic loss to the pig production. The present report describes the rare cases of Mycoplasma hyopneumoniae induced fibrinous pericarditis in post-weaned crossbred piglets (n=7). The piglets showed the lesions of fibrinous pericarditis, sac effusions (blood and serosanguineous), heavy non-collapsible lungs, and fibrinous hepatitis. Microscopically, sub-acute fibrinous pericarditis, pleuritis, broncho-interstitial pneumonia, hepatitis, fibrinous polyserositis, lymphocyte depletion and enteritis were characteristic lesions. Immunohistochemical staining showed abundant immunoreactivity of M. hyopneumoniae antigen in the infiltrating mononuclear cells of heart, bronchiolar epithelium and cellular exudates of lungs, and lymphocytes of lymphoid organs. The etiological confirmation of M. hyopneumoniae in all the tissues by the PCR test showed amplification of 853bp targeting the p36 gene. The phylogenetic tree showed 99.30% homology with that of M. hyopneumoniae sequences in the database. The other likely aetiologies like PM, APP, SS, HPS, B. bronchiseptica , Chlamydia, PRRSV, SIV, and ECMV were tested negative by PCR, except for PCV2 in lung samples. This paper highlights the importance of M. hyopneumoniae in the differential diagnosis of fibrinous pericarditis in piglets.