Parentstock Rearing 1731.jpg

Published on Oct. 19, 2020

Avian Encephalomyelitis (AE) in chickens

Avian encephalomyelitis (AE) or epidemic tremor is an infectious viral disease affecting chickens, turkeys, pheasants and quail.

Avian encephalomyelitis virus (AEV) is an enterotropic virus, infectious by the oral route. The virus replicates in the intestine and is excreted in the feces.

Infected litter spreads the virus either via direct bird to bird contact or via fomites (contaminated equipment, vehicles, people, …).

Besides this horizontal transmission, AEV can also be vertical transmitted. When susceptible parent stock flocks get infected after sexual maturity, they will infect part of their progeny during the period of viremia (about 2 weeks).

In young birds, primary infection takes place in the alimentary tract, followed by a viremia and subsequent infection of the central nervous system (CNS). In older birds, infected orally, no viral antigen is found in the CNS, explaining why infected adults show no neurological signs.

AEV is a Picorna virus, quite resistant to environmental conditions.

Clinical Signs

Ataxia and tremors of the head and neck in 1-2 weeks old chicks are typical. No significant macroscopic lesions are seen in affected birds, but some survivors can develop cataracts at later age.

There seems to be a marked age resistance starting around 3 weeks of age.

Mature birds can show a temporary drop in egg production but do not develop neurologic signs. In breeder flocks, hatchability also drops due to late embryonic mortality.


Clinical history, histology of the brain and antigen detection are conclusive. The brain is the best source for PCR or virus isolation.

Serology can be done with Elisa.

AE 2.CESAC..jpg

Control & Vaccination

Maternal derived antibodies (MDA’s) fully protect chicks against disease. Parent stock must be vaccinated at least 4 weeks before the onset of lay.

It is also advised to vaccinate commercial layers to prevent a drop in egg production.


  • Diseases of Poultry 14th Edition. David L. Suarez
  • Picture of affected chicks: CESAC

Related articles

, by
Infectious Laryngotracheitis (ILT) in Chickens

Infectious Laryngotracheitis (ILT) is a highly contagious respiratory disease caused by an Herpesvirus (GaHV-1 commonly known as ILTV). Chickens, pheasants and peafowl are susceptible to the disease.…

, by
Infectious Bursal Disease (Gumboro) in Laying hens

Infectious Bursal disease, also known as Gumboro disease, is caused by an avibirnavirus (IBDV) and affects the immune system of young chicks throughout the world. The virus has no envelope and is ver…

, by
Avian Leukosis Virus (ALV) in Laying hens

Avian leukosis virus (ALV) is an oncogenic virus, an infectious disease causing tumors in poultry.ALV is a retrovirus, an RNA virus and is divided in six subgroups: A, B, C, D, E and J.Endogenous leu…