As intensive farming models grow, the backdrop of antibiotic restrictions and reduced reliance on antibiotics has made poultry diseases increasingly complex. Take 2024, for example—new outbreaks of old diseases stood out sharply.
Immunosuppressive diseases like infectious bursal disease, swollen head syndrome, and viral arthritis have hit farmers hard, with reduced egg production in flocks often popping up in specific regions.
Of course, several diseases can cause egg production to drop, including Newcastle disease, avian influenza, infectious bronchitis, and rhinitis. Industry observations and data show egg drop syndrome has a higher detection rate in areas with dense layer and breeder chicken farms, clearly creating challenges for existing immunization programs.
What is Egg Drop Syndrome?
Egg Drop Syndrome (EDS’76) is a disease caused by an adenovirus, mainly hitting laying hens—especially those at peak production—causing a sharp drop in egg output and poor eggshell quality. While outbreaks mainly affect laying hens, ducks and geese are typically considered the natural hosts of EDSV. The virus has a long latent period and can spread vertically and horizontally. Horizontal transmission is slow and intermittent, taking about 11 weeks to spread through an entire cage.
Clinical Symptoms of Egg Drop Syndrome
- Drop in Egg Production: Egg production falls suddenly and rapidly, lasting 4-10 weeks, with output potentially dropping by 40%-50%. Production may recover later, but the total loss is typically 10-16 eggs per hen.
- Abnormal Eggs: Thin-shelled, soft-shelled, and shell-less eggs are common. Thin-shelled eggs are often rough or have a granular texture at one end; egg whites may become thinner, and eggs may occasionally be smaller.
- Flock Health Status: The flock’s overall health shows no major issues, though reduced appetite and lethargy may occur. Infected flocks may have brief diarrhea.
Diagnosis of Egg Drop Syndrome
- Clinical Diagnosis: When healthy hens show eggshell changes alongside a sudden drop in egg production, suspect EDSV infection. Carefully check eggshell changes—shell-less, soft-shelled, and thin-shelled eggs, beyond deformed eggs, are hallmarks of EDS.
- Laboratory Diagnosis: Antibodies in unvaccinated flocks signal infection. However, in most cases, especially in offspring infected vertically via eggs, virus shedding and detectable H antibodies only show up when egg production hits 50%. This makes detecting carrier chickens with ELISA and PCR tough and often delayed, but it can confirm the diagnosis.
Prevention and Control of Egg Drop Syndrome
- Boost Biosecurity: The virus is locally prevalent and somewhat resistant to inactivation. Strict control of personnel and vehicle access, regular disinfection, and timely cleaning of poultry houses, equipment, and especially manure are critical.
- Breeder Management: Regularly screen breeder chickens and cull those carrying the virus.
- Vaccination: Vaccinating against egg drop syndrome is a solid preventive step. Flocks are typically vaccinated before laying starts, at 14-16 weeks of age. Antibody levels peak 2-5 weeks after vaccination, with immunity lasting at least a year. The imported Israeli EDS inactivated vaccine (strain 127) from Vioran Feather Co. triggers a strong antibody response and protects flocks against virulent strains.
Treatment of Egg Drop Syndrome
No specific drugs effectively treat egg drop syndrome, so prevention is key. Pay attention to controlling related diseases like infectious bursal disease and Mycoplasma synoviae, which can weaken immunity. As soon as symptoms are detected in a flock, isolate it, ramp up disinfection to stop disease spread, and add vitamins and minerals to boost immunity and help restore egg production.
