The disease is spread '''horizontally''', via the faecal-oral route and chicks from non-immune layers under the age of three weeks are neurologically affected. '''Vertical transmission''' can also occur from infected layers to their chicks. The virus may be shed for several weeks. Once a bird becomes infected with the disease or is vaccinated it is immune to AE for life, some birds are left blind. AE is not considered a zoonosis. | The disease is spread '''horizontally''', via the faecal-oral route and chicks from non-immune layers under the age of three weeks are neurologically affected. '''Vertical transmission''' can also occur from infected layers to their chicks. The virus may be shed for several weeks. Once a bird becomes infected with the disease or is vaccinated it is immune to AE for life, some birds are left blind. AE is not considered a zoonosis. |