Microscopic lesions of naturally occurring and experimental "spiking mortality" in young broiler chickens.

Tissues from five chickens from each of 44 flocks affected with "spiking mortality" were examined histologically. Tissues from these chickens were characterized by: multifocal necrosis of hepatocytes with congestion and blood lake formation; severe lymphocyte necrosis in the bursal medulla, thymic cortex, and gut-associated lymphoid tissues; acute necrotic vasculitis in the alimentary serosa and liver; rickets; and air-sac disease in survivors. No specific etiology was identified in sections examined.