Investigation of bovine dilated cardiomyopathy in Holstein-Friesian cattle in the UK

Bovine dilated cardiomyopathy (BDCM) is a primary disease of the heart muscle that has been reported in Holstein-Friesian cattle worldwide in the last twenty years. Histopathological, immunocytochemical and morphometrical analyses were conducted on heart tissue obtained from two groups of cattle: nine animals diagnosed with BDCM and nine unaffected animals matched for sex, breed and age. Histopathology revealed marked perimysial and endomysial fibrosis, extensive cardiomyocyte loss with two different morphological appearances, increased variation in myofibre cross-sectional area, multifocal myocyte disarray and vacuolation. Morphometrical analysis identified an approximate 7-fold increase in connective tissue and it is suggested that the degree of increased fibrosis in bovine cardiac muscle is a reliable discriminator for BDCM. Post-analysis calculations estimated a near 50% loss of cardiomyocytes with a 2.5-fold increase in size of surviving cardiomyocytes in animals with BDCM. Possible pathogenetic mechanisms leading to the cardiac failure are discussed. Diffuse or multifocal myocardial infiltration by T-lymphocytes was also observed, suggesting a possible viral aetiology. However, quantitative Taq-Man(R) PCR analysis failed to provide evidence of bovine enterovirus infection.