Canine parvovirus myocarditis: clinical signs and pathological lesions encountered in natural cases

Canine parvovirus (CPV) myocarditis was diagnosed in 11 puppies during 1979. The diagnosis was made at histopathological examination on the basis of 2 characteristic lesions: a subacute to chronic fibrous myocarditis and the presence of large, basophilic intranuclear inclusions in the cardiac myofibres. The puppies varied from 31/2 to 8 weeks of age and all died suddenly without prior symptoms except for 1 pup which developed a severe respiratory dyspnoea 12 h before death. The presence of white bands or streaks of fibrosis on the endocardial or epicardial surfaces of the ventricles was a characteristic gross finding in 65% of cases. In all cases the lungs revealed a pneumonitis noted as hypercellularity and thickening of the alveolar walls. Alveolar macrophages were present within the alveolar lumens. The latter lesion was regarded to be secondary to heart failure. The clinical symptoms and pathological lesions observed are discussed and compared to these noted by various other workers both in South African and in other countries.