Egg drop may be defined as a sudden drop in egg production or a failure to achieve a normal peak in production. In the autumn of 1976 a distinct egg drop syndrome was first identified in Northern Ireland. Apparently a similar disease had been seen over a 4-year period in broiler parents in Holland. The cause has been identified as Adenovirus BC14, 127, first isolated in Northern Ireland in 1976. It affects chickens and has occurred in Ireland, Holland, France, England, Germany, Spain, Peru, Brazil, Uruguay, Argentina. Mortality is usually negligible. Circumstantial evidence suggests that the main route of transmission is through the eggs (vertical transmission) followed by latent infection during rear with viral excretion starting shortly before sexual maturity. Lateral transmission from bird to bird is slow and may be prevented or slowed for weeks by netting divisions. Contamination of egg trays at packing stations may play a part in transmission, as may wildfowl and biting insects. Clinical disease occurs during sexual maturity. Spread from house to house may take 5-10 weeks. Unvaccinated flocks with antibodies before lay do not peak normally. The infection is commonly present in ducks and geese but does not cause disease.

Signs

Egg drop at peak or failure to peak. Drops may be of 5 to 50% and last for 3-4 weeks.

Rough, thin or soft-shelled eggs and shell-less eggs.

Loss of shell pigment.

Poor internal quality.

Lack of signs in the birds themselves.

Prevention

Vaccination with inactivated vaccine prior to lay.

Information taken from the poultrysite.