Intra-cardiac autonomic neuropathy in Holstein-Friesian dairy cows affected with bovine dilated cardiomyopathy

Three Holstein-Friesian dairy cows, aged 5 1/3 to 12 years, showed a history of heart failure and were euthanized on separate days. Commonly observed postmortem findings included edema in many sites of the body, dilatation and hypertrophy of the right cardiac ventricle, hepatic congestion, and swollen pale kidneys. Histopathologically, myocardial lesions were comprised of a variety of degenerative changes in cardiomyocytes and interstitial fibrosis, consistent with those described previously in cases of bovine dilated cardiomyopathy in Holstein-Friesian cattle. Additionally, in one of these three cows, unmyelinated nerve fibers of many intra-cardiac nerve bundles that probably were postganglionic fibers exhibited multifocal segmental degeneration of axons. Degenerated axons were closely associated with Schwann cell pathology, indicating an intimate involvement of axon-Schwann cell interaction. Such an intra-cardiac autonomic neuropathy might have had an adverse effect on the regulation of heart activity. It is not possible to determine if this intra-cardiac autonomic neuropathy was primary or secondary to the dilated cardiomyopathy.