Immunohistochemical Detection of Encephalomyocarditis Virus (EMCV) Antigen in the Heart of Experimentally Infected Piglets

Seven 40-day-old piglets were inoculated with encephalomyocarditis virus (EMCV) strain 424/90, isolated from an outbreak of the myocardial form of the disease in Greece. Two non-infected animals were used as controls. Of the seven inoculated piglets, five died suddenly on day 1·5, 2 (two piglets), 2·5 or 4 post-inoculation (p.i.). The remaining two and the control piglets were killed on day 8 p.i. EMCV antigen was detected immunohistochemically in endothelial cells of capillaries from 1·5 to 2·5 days p.i. only, but was found in cardiac muscle cells, Purkinje fibres and macrophages on all occasions up to day 8 p.i. In endothelial cells and macrophages, EMCV antigen was detected intracytoplasmically, but in cardiac muscle cells and Purkinje fibres it was observed intracytoplasmically or intranuclearly, or both. The frequent presence of EMCV antigen in Purkinje fibres suggests an explanation for the sudden death of the piglets.