Egg Drop Syndrome’76


There are many causes of a sudden drop in egg production of domestic fowl. This particular disease is caused by a haemagglutinating adenovirus and manifests as a loss of shell pigmentation, production of soft-shelled and shell-less eggs, and a sudden drop in egg production lasting several weeks. There are no other significant clinical signs in affected birds. Experimental infection reveals oedema and inflammatory exudate in the shell-gland. The virus is derived from ducks, geese and muscovies, but once introduced into chickens can be spread vertically and horizontally via contaminated eggs, on equipment (including egg trays), and in faeces etc; although lateral spread in caged layers may be slow. Vaccination of pullets is a widely practiced, effective preventive strategy. Infection in ducks is probably associated with reduced shell quality and reduced egg production.

Diagnosis and tests available


Diagnosis is based on a sudden drop in egg production in non-vaccinated chickens, associated with poorly pigmented, thin-shelled and shell-less eggs. Histology of field cases is not reliable; virus isolation is not required.

Tests available


Sample(s) required

Days of the week test is conducted

Turnaround time1

Egg drop syndrome virus HI Test

Clotted bood (red top tube)

Within 1-2 days of receipt

1-2 days2

Egg drop syndrome VNT

Clotted blood (red top tube) or lithium heparin blood (green top tube)

Batch tested Wednesday & Friday

1 week2

1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.
2 Confirmation testing of positives may affect turnaround time.

Specimen requirements

Blood (with anti-coagulant)

  • 10 ml of blood (including at least 2 ml of serum) from each of at least ten affected birds
    • Collected into a lithium heparin tube
    • Submit chilled

Blood (without anti-coagulant)

  • 10 ml of blood (including at least 2 ml of serum) collected into a plain red top tube
    • Submit chilled


Fees for tests undertaken to confirm or exclude a diagnosis of Egg drop syndrome’76 are paid by NSW Department of Primary Industries. Extra testing to establish an alternative diagnosis is at submitters’ expense.