Outbreaks in Quebec pig farms of respiratory and reproductive problems associated with encephalomyocarditis virus

Abstract

Encephalomyocarditis virus (EMCV) was isolated from tissues of aborted fetuses and weaned and suckling piglets from 4 different pig farms in Quebec. The farms were experiencing reproductive failure in sows of different parities concomitant to respiratory problems in suckling and postweaning piglets. At necropsy, gross lesions were confined to the lung and consisted of pulmonary congestion and edema of various degrees. Lesions of multifocal interstitial to proliferative pneumonia were found in the lungs of these piglets. Bacteriologic examination of various tissues from necropsied pigs yielded no pathogens in most cases. No significant antibody titers against 3 swine viruses (transmissible gastroenteritis virus, porcine parvovirus, and swine influenza virus) and two bovine viruses (bovine viral diarrhea and infectious bovine rhinotracheitis viruses) were detected in the sera of convalescent pigs. The Quebec EMCV isolates were antigenically related to the reference ATCC-VR129 strain of EMCV, as demonstrated by indirect immunofluorescence, serum neutralization (SN), and Western immunoblotting. However, one of the Quebec isolates could be distinguish by SN. EMCV-specific SN antibody titers up to 1:12,800 were detected in thoracic and ascitis fluids of aborted fetuses and in sera of convalescent pigs. A possible pneumotropic EMCV variant in swine may exist.