Studies on an ascitic syndrome in young broilers. 2. Ultrastructure.

Hearts, livers and kidneys of young broiler chicks with an ascitic syndrome were examined by electron microscopy. The results confirmed a histopathological study performed on material from the same birds. Ultrastructural observations included cardiac myofibril damage, marked dilation of lung parabronchi and associated air spaces, mitochondrial alterations and excess lipid in kidney tubules together with thickening of glomerular basement membranes. Light and dark degenerative cells and a paucity of glycogen were common findings in livers. Inflammatory cells, in particular immature and mature heterophils, were often seen in hearts and livers. Enveloped virus-like particles in the order of 100 nm were seen in all organs of affected birds, but not in those of controls. Although the aetiology of the syndrome is obscure, there were strong similarities in the ultrastructural findings in these birds and those reported by others in hypoxic birds maintained at altitude. Together with the viral implications, the reported syndrome may be multi-factorial in origin.