Sudden death associated with Neospora caninum myocarditis in a dog.

A 10-month-old female Bull Mastiff dog was found dead without reports of any prior clinical signs of disease. Necropsy revealed lesions in the myocardium, which consisted of a large 2 x 2.3-cm brownish area and a few small similar lesions. Microscopically, Neospora caninum tachyzoites were found in the lesions characterized by necrosis and interstitial myocarditis. Diagnosis was confirmed by immunohistochemical staining with anti-N caninum serum.