Light and electron microscopic changes in the myocardium of influenza-infected turkeys

Virus isolation and titration, electrocardiography, enzyme assays and light and electron microscopic studies were undertaken in male turkeys infected with influenza A/turkey/Ontario/7732/66 virus to determine its potential role in the genesis of heart disease. Virus was isolated from the heart initially before a demonstrable viremia and terminally in declining serum viral titer. Virus was isolated from the heart muscle as early as 1 day postinoculation. Highest viral titers were found in the heart at 6 days postinoculation and coincided with maximum elevations of serum glutamic-oxalacetic transaminase and lactic acid dehydrogenase, microscopic lesions in the heart and cardiac arrhythmias. Microscopic lesions in the heart were first detected at 4 days postinoculation and consisted of disseminated areas of necrosis, focal myocarditis, pericarditis and endocarditis. Alterations in myocardial ultrastructure which followed viral infection included fragmentation and dissolution of myofibrils, dilation of the sarcotubular system, increase in membrane vesicle formation in the region of the endoplasmic reticulum, discontinuity of the sarcolemma, proliferation of mitochondrial population, swelling of mitochondria with separation and disruption of the cristae, and the presence of intramitochondrial and perinuclear densities.