Anaemia-dermatitis of broilers: field observations on its occurrence, transmission and prevention.

Anaemia-dermatitis was first observed in German broiler flocks in 1977. Its frequency has increased in the past six years. Atrophy of thymus, bursa and bone marrow occur and are affected by a severe anaemia and immunosuppression. Secondary bacterial infections of the skin cause gangrenous dermatitis. Systematic investigations of outbreaks in two broiler integrations showed the syndrome to occur only in the offspring of young broiler breeders during the first 3 to 9 weeks of production. Anaemia could be reproduced experimentally in CAA-antibody negative SPF birds by injecting a bacteria-free filtrate of organ homogenates of diseased birds; birds kept in contact with the inoculated chicks remained healthy. It is concluded that anaemia-dermatitis is primarily caused by the chicken anaemia agent (CAA). Vertical transmission via hatching egg predominates with no evidence of horizontal transmission. In order to prevent egg transmission of CAA immunisation during rearing is indicated for breeder stocks.