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United Kingdom

Avian Encephalomyelitis

Layer chicken with blue background


Avian encephalomyelitis (AE) is a viral disease of poultry caused by an enterovirus belonging to picornavirus group and is characterised by neurologic signs. Infection occurs via vertical and horizontal transmission. If a breeder flock becomes infected during egg production, the virus is vertically transmitted to the offspring and a major outbreak occurs. Young chickens can also be infected on the farm. The incubation period varies from 5-14 days depending on the route of infection. AE virus is resistant to environmental conditions and may remain infectious for long periods.


  • Drop in production and hatchability in breeders

  • Clinical tremors of the head and neck and increased mortality in young birds

  • Ataxia (affecting coordination and balance) and leg weakness

  • Increased mortality

Diagnosis is mainly based on histological examination of the brain, proventriculus and pancreas. The diagnosis is best confirmed by isolation and identification of the virus. Tissues collected for virus isolation must include the brain and duodenum with the pancreas. In adults, serological testing helps establish the diagnosis.

Currently there is no effective treatment for AE.

Preventative vaccination of breeder pullets and layer pullets with live AE vaccine several weeks before they come into lay is the only effective way of AE control. Vaccination prevents vertical transmission of the virus to chicks by providing the chicks with a sufficient level of maternally derived antibodies because there is only one serotype for the AEV.