Why does an infection of Avian Encephalomyelitis (AE) in non-immune laying flocks cause a sudden, temporary drop in egg production and hatchability?

Avian Encephalomyelitis (AE), commonly known as epidemic tremor, is a picornavirus infection that primarily affects young chicks, causing severe neurological tremors and ataxia. However, when the virus infects non-vaccinated, fully active laying or breeder flocks, the clinical presentation is different. The AE virus is highly epitheliotropic in adult birds, rapidly replicating within the ovary and oviduct tissue. This viral replication causes moderate localized inflammation, resulting in a sudden, temporary drop in egg production of 10% to 15% that lasts for exactly 10 to 14 days. More critically, if the flock is a breeder flock, the virus is vertically transmitted to the hatching eggs. This egg-borne infection causes massive embryonic mortality during the final stages of incubation, and any surviving chicks will hatch with severe tremors and paralysis. To prevent these losses, pullets must be vaccinated with a live AE vaccine (often combined with Fowl Pox) via wing-web puncture at 10 to 14 weeks of age. Farmers can read neuro-virology in the Poultry Encyclopedia, buy certified AE-Pox vaccines on Poultry Plaza, track daily egg and chick prices on Poultry Rates, and trade on Murghi Mandi.