Virus isolation studies in an outbreak of porcine encephalomyelitis.

An outbreak of central nervous system disease affecting young pigs occurred in the fall of 1981 in eastern Ontario. A diagnosis of viral encephalomyelitis was made on pathological grounds and virus isolation studies were subsequently initiated to determine the causative agent. Cultural isolation procedures using several biological systems failed to detect virus in nervous tissues from affected animals. Direct extraction of similar tissues by combined biochemical and biophysical procedures yielded nonenveloped , spherical particles with a diameter of 30 nm and a buoyant density of 1.34 g/mL in CsCl. A tentative diagnosis of enterovirus infection was made on this basis.