Idiopathic myocardial fibrosis in captive chimpanzees (Pan troglodytes)

Cardiovascular disorders and, predominantly idiopathic myocardial fibrosis, are frequently associated with mortality among zoo-housed chimpanzees (Pan troglodytes). Formalin-fixed whole hearts of deceased chimpanzees housed in zoos (n=33) or in an African sanctuary (n=2) underwent detailed macroscopic and histopathologic examination using a standardized protocol. Archived histological slides from the hearts of 23 additional African sanctuary-housed chimpanzees were also examined. Myocardial fibrosis (MF) was identified in 30/33 (91%) of the zoo-housed chimpanzees but none of the 25 sanctuary-housed chimpanzees MF was shown to be characterized by both interstitial and replacement fibrosis. Immunophenotyping demonstrated that these fibrotic lesions were accompanied by the increased presence of macrophages, alpha smooth muscle actin-positive myofibroblasts and a minimal to mild T-cell dominant infiltration. There was no convincing evidence of cardiotropic viral infection, or suggestion that diabetes mellitus or vitamin E or selenium deficiency are associated with the presence of the lesion. However, serum vitamin D concentrations among zoo-housed chimpanzees were found to be lower in seasons of low UV light levels