Myocarditis in 9- and 11-day-old broiler breeder chicks associated with a reovirus infection.

Nine- and 11-day-old male broiler breeder chicks from a flock with excessively high mortality were found to have ascites, fibrotic and necrotic livers, and round, thin-walled hearts. Virus isolation on liver homogenates and sequencing of PCR products of the isolate identified a reovirus whose sequence varied from sequences of other published reoviruses. Histopathology supported a diagnosis of reovirus-associated myocarditis and myocardial necrosis. This virus was possibly transmitted vertically from the primary breeder flock.