Avian encephalomyelitis (AE) in broilers is a viral disease of the central nervous system caused by the avian encephalomyelitis virus (AEV), a picornavirus of the genus Tremovirus. It is classically a disease of young chicks (1–3 weeks), as there is an age resistance. It is primarily linked to vertical transmission from infected breeder flocks, which results in neurological signs and early mortality in the progeny.