Identity

A viral infectious disease of laying chickens caused by Duck Adenovirus 1. It replicates in the pouch shell gland (uterus), causing a sudden drop in egg production and the laying of shell-less, soft-shelled, pale, or sand-paper-like eggs.

Overview

Egg Drop Syndrome-76 (EDS-76) is a high-priority viral pathogen of laying chickens caused by Duck Adenovirus 1, a virus whose natural hosts are waterfowl. It targets the reproductive system (specifically the uterine mucosal epithelium), leading to a loss of calcium-depositing capability. This results in pale, soft-shelled, completely shell-less, or rough eggs, causing severe economic losses. Transmission occurs vertically from breeders, horizontally via contaminated egg trays, and laterally from waterfowl. Prevention depends on separating chickens from waterfowl, disinfecting egg trays, and administering inactivated oil-emulsified vaccines prior to the onset of lay.

Structured Facts

Classification

Viral > Infectious Pathogen

Epidemiology

• Prevalence in India: High commercial importance in table egg and breeder sectors
• Severity: High
• Affected Species: Poultry (Layers and Breeders); accidental host from waterfowl
• Affected Age: Laying hens at peak of production (25 to 35 weeks of age)
• Transmission: Vertical (transovarian), horizontal (contaminated egg trays/water), lateral (waterfowl reservoirs)
• Mortality: Negligible (< 1%)
• Morbidity: Variable (horizontal spread is slow/silent until sexual maturity)
• Economic Importance: High (downgraded, unsalable eggs)

Clinical Signs

• Early/Intermediate: Clinically healthy laying flock with sudden reduction in egg production (10% to 40% drop lasting 4-10 weeks)
• Advanced: Thin-shelled, soft-shelled, shell-less, rough/chalky/sand-paper-like eggs. Loss of pigment in colored eggs. Targets Reproductive system (pouch shell gland).
• Postmortem Findings: Mild uterine edema, mucosal pallor, and focal cellular infiltration in the shell gland epithelium. Ovarian follicles remain normal.

Diagnosis

• Field Diagnosis: Sudden drop in lay with characteristic eggshell defects in an otherwise healthy flock
• Laboratory Tests: Hemagglutination (HA) and Hemagglutination inhibition (HI) tests using avian erythrocytes, PCR (hexon gene), virus neutralization tests
• Differential Diagnosis: Infectious Bronchitis, Newcastle Disease, Mycoplasmosis

Treatment

• Immediate Actions: Disinfection of recycled egg trays, isolation from waterfowl
• Medicines: None exist

Prevention

• Vaccination: EDS-76 Inactivated / ND+IB+EDS Killed (Intramuscular/Subcutaneous injection at 14 to 16 weeks, prior to onset of lay)
• Biosecurity: Separation of chicken farms from domestic waterfowl, chemical disinfection of egg trays
• Farm Management: Monitor hatchery vertical transmission

Quantitative Data

• Morbidity Rate: Variable
• Mortality Rate: < 1%
• Egg Production Drop: 10% to 40%
• Duration of Drop: 4 to 10 weeks
• Target Age: 25 to 35 weeks

Relationships

• Vaccines: EDS-76 Inactivated, ND+IB+EDS Killed
• Medicines: None
• Biosecurity: Egg tray disinfection, Waterfowl separation
• Vector: Domestic and wild waterfowl