Abstract. Severe necrotizing myocarditis associated with canine parvovirus type 2 (CPV-2) infection and diffuse leukoencephalomalacia was recognized in a 4-week-old mongrel puppy. The cardiac lesions were characterized by severe diffuse myocardial degeneration and necrosis with occasional massive mineralization and distinct intranuclear inclusion bodies. Immunohistochemical examination revealed the presence of CPV-2 antigens in both the cytoplasm and nuclei of the myocytes. In the white matter of the cerebrum, moderate to severe diffuse necrosis with diffuse infiltration of gitter cells and occasional diffuse mineral deposits were recognized symmetrically and bilaterally. In the meningocortical area of the cerebellum, there was mild focal hemorrhage and accumulation of hemosiderin-laden histiocytes. In addition to the absence of viral antigen (as judged by immunohistochemistry), neither viral inclusions nor other vascular lesions were identified in examined sections of brain. These findings suggest that the brain lesions were not induced by direct CPV-2 infection but were related to severe myocardial lesions producing prolonged hypoxia and/or ischemia.Key words: Canine parvovirus; leukoencephalomalacia; myocarditis.Canine parvovirus (CPV) has been widely known as a pathogen of significant worldwide canine disease since 1978. 1 The virus, thought to be a mutation of feline panleukopenia virus (FPV), is classified into several serotypes, CPV-1 (minute virus), CPV-2, CVP 2a, and CPV 2b. 13 Three forms of the disease are recognized, the enteric form, the cardiac form, and the neurologic form. 2,4,6 The lesions of the disease are readily identified by pathologists by the finding of severe necrotizing enteritis, nonsuppurative myocarditis, or disseminated necrotizing vasculitis 6,9 and the finding of intranuclear basophilic inclusion bodies in the intestinal cryptal epithelium, myocytes, and vascular endothelium. 1,[3][4][5]7,9 Only a few reports describe the neurologic form of CPV, which includes leukomalacia 6 and encephalitis. 2 In this report, we describe CPV-2 associated with massive necrotizing myocarditis and diffuse leukoencephalomalacia and discuss the possible pathogenesis of these lesions.A pregnant mongrel dog found lying on the road was immediately brought to a private animal hospital. At that time, she had begun to give birth to the first puppy. Although the first puppy was delivered with assistance and died the next day, the other four puppies were born spontaneously the next day. The remaining four puppies grew normally but were severely anemic when examined at 25 days of age. Three died within the next 4-5 days. A puppy that died at 27 days of age was submitted to our laboratory for necropsy. At necropsy, the mucosal layers of the eyelid and oral cavity, the subcutaneous tissues, and the internal organs were pale, including the heart, which was diffusely pale. There were no significant gross lesions in the brain except for a mild but diffuse edematous change. There were 15 adult ascarid parasites in t...