| Abstract: | The myocardial lesions of pigs (age from 2.5 to 3.5 month) with encephalomyocarditis virus infection are presented. The disease is caused by members of the genus Cardiovirus (family Picornaviridae). In Greece it was first observed 1987 in two stables of pig-breeders with a mortality of 80%. The macroscopic changes are characterized by a myocardial degeneration with greyish pale linear or round foci and by an accumulation of a clear red to yellow fluid in the pericardium and the pleural cavity. The most important histologic changes of the hearts are a diffuse or focal myocarditis with a severe infiltration of histiocytes, lymphocytes and plasma cells. Furthermore, degeneration and necrosis of cardiac muscle cells are observed. Electron microscopic investigations of the myocardial cells reveal mild mitochondrial edema, severe perinuclear and intranuclear edema, myelin figures, intra cisternal sequestrations of the rough endoplasmic reticulum, disorganization of the myofibrillar Z-line, and crystalloid viral structures between the mitochondria. Polyribosomes and accumulations of viral particles are frequently found in membrane bound cysts within myocardial cells and the capillaries. Furthermore, viral particles (single or in cysts) and crystalloid viral structures are observed in the cytoplasm of edematous endothelial cells. |
