Pleural effusion disease in rabbits. Histopathological observations.

Pleural effusion disease (PED) is a generalized infection of laboratory rabbits caused by an unidentified agent, believed to be a virus. The histopathological response of 17 rabbits infected experimentally with this agent was studied. The light microscopical changes were minimal and the most consistent findings were alterations of the lymphoid tissue. Fatal infections were characterized by a uniform reduction of the splenic white pulp, focal degenerative changes of the thymus and lymph nodes and probably slight proliferative changes of the kidney glomeruli. In surviving animals there were transient myocardial and hepatic lesions and, after clinical recovery, proliferative changes in spleen, lymph nodes, interstitial lung tissue and probably kidney glomeruli. The results do not permit any conclusions to be drawn regarding the aetiology or the pathogenesis of PED infection.