Egg Drop Syndrome(EDS)

Egg Drop Syndrome (EDS), a viral disease first reported in Europe in 1976, is a productivity-lowering disease that occurs exclusively in laying chickens and is characterized by abnormal eggs, including deformed, soft, discolored, and uneven eggs, with no visible clinical symptoms.

Clinical Symptoms

There are no clinical symptoms specific to the disease, which is characterized by poor laying and abnormal eggs.

Brown birds are more susceptible and the first symptom after infection is depigmented eggs, which are characterized by the loss of egg shell pigment.

Depigmented eggs are immediately followed by the production of soft, hard, soft, and blue eggs.

In the case of soft eggs, the egg shell becomes very rough and bumpy.

In this case, the removal of the apparently malformed eggs usually has no effect on fertilization or hatchability.

Poor egg production usually lasts for 4-10 weeks, with a 6-25% reduction in egg production compared to normal, and returns to normal after 6-8 weeks.

Chickens infected before or after the start of laying do not reach peak egg production.

Individuals with anorexia and diarrhea are occasionally observed, but these are not characteristic clinical symptoms, and ovarian abnormalities and oviductal atrophy are occasionally observed at necropsy, but these are also not characteristic findings.

Diagnosis

Failure to reach the normal laying peak or abnormal egg production in conjunction with watery diarrhea may indicate the presence of EDS '76.

In cage-reared laying hens, EDS '76 infection may result in eggless production, with the floor of the cage covered with egg white and egg yolk, and given the slow rate of disease transmission, careful observation of infected and uninfected groups within the flock is warranted.

However, poor egg production with malformed eggs can be caused by other factors and should be supported by laboratory diagnosis by virus isolation or serology (hemagglutination inhibition (HI) test).

Prevention and treatment

There is no effective treatment, and effective prevention of EDS '76 requires vaccination in conjunction with hygienic specimen management.

The tetrodotoxin vaccine is used and it is mainly a problem during the peak of laying, so it is necessary to vaccinate 4 weeks before the start of laying (16~18 weeks old) to prevent infection during the laying period.

Chicks should be introduced from a vaccinated mother and should not be contaminated by crates, etc.