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Egg Drop Syndrome

Egg drop syndrome (EDS) is an infectious disease caused by an adenovirus which mainly affects laying hens. The disease results in egg quality defects in the eggs laid by infected hens. Egg drop syndrome virus (EDSV) or Duck adenovirus-1 (DAdV-1), originated in waterfowl and likely introduced to commercial chickens through a contaminated vaccine. Ducks and geese are the natural hosts for the virus, and are often asymptomatic carriers. The virus is spread both vertically and horizontally. The primary site of replication of the virus is the pouch shell gland. In infected embryos or young birds, DAdV-1 is latent until onset of laying eggs.

The first sign of infection with EDSV is a change in the color of the egg, quickly followed by production of smaller-the-normal eggs, shell-less, thin-shelled, or soft-shelled eggs, and either a rapid or extended loss in egg production of up to 40%. Clinical signs are mainly associated with egg production. EDS will need to be distinguished from Infectious Bronchitis (by absence of respiratory signs and typical misshapen eggs), Newcastle disease, Avian Influenza (by absence of illness), and severe vitamin D3 deficiency.


Reduction in production with the occurrence of depigmented, soft-shelled eggs in the absence of other clinical signs should trigger consideration of EDS. The sensitivities of various serologic assays, including agar gel precipitin (AGP) assay, ELISA, Hemagglutination-inhibition (HI), and serum neutralization, are similar for detecting antibodies to EDS virus.

Clinical Signs

Misshapen eggs
Change in egg color
Laying soft (thin)/shellless eggs
Decreased egg production


  • History
  • Clinical signs
  • Viral isolation


No treatment is generally required unless secondary reproductive-related complications arise.::



  • Biosecurity
  • Vaccine - Inactivated vaccines with oil adjuvant are available and, if properly made, control the disease. They reduce but do not prevent virus shedding.

Scientific References

Risk Factors

  • Keeping ducks and other waterfowl together with laying hens.