Necrotic, haemorrhagic, hepatomegalic hepatitis associated with vasculitis and amyloidosis in commercial laying hens

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Abstract
A 60,000 layer flock in a multi‐age commercial operation experienced high weekly mortality ranging from 0.17% to 0.36% starting at 40 weeks of age. The most prominent post‐mortem findings were enlargement of the liver and spleen (up to 3 times normal) and liquid blood in the abdominal cavity. Microscopic examination of the liver revealed large or small areas of coagulative necrosis and occasional granulomas. Small pools of amorphous eosinophilic material were found around some areas of necrosis and cords of hepatocytes were separated by pink‐staining material. There was generalized lymphoid depletion and multifocal areas of interwoven, light pink‐staining material in the spleen. The pink material was shown to contain amyloid by Congo red staining. A vasculitis, characterized by the proliferation of inflammatory cells within and around the portal veins, was also observed. These findings tend to strengthen a theory that ‘hepatitis‐liver hemorrhage syndrome’ could be precipitated by a continuous immune response to an infectious agent such as would occur by vaccination with a live vaccine that continues to replicate in the body or with an inactivated vaccine containing a slow‐release adjuvant.

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