Invasion of avian encephalomyelitis virus from the gastrointestinal tract to the central nervous system in young chickens.

Invasion sites of avian encephalomyelitis virus in the internal organs of orally infected chicks were determined by the immunofluorescent method. The invasion began when the epithelium tunica mucosae of the duodenum (together with the proventriculus, jejunum, or cecum in certain birds killed at postinoculation day 1) became test-positive. Viremia persisted for more than 5 days in the early stage of infection, then the pancreas was rapidly infected, followed by the liver, kidney, and spleen. Subsequently, the virus spread to the CNS. Rapid infection of the duodenum and pancreas was clearly observable.