Egg drop syndrome

EDS '76 is one of the important viral diseases of birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds . EDS '76 is one of the important viral diseases of birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds . Previously, this disease was commonly named as merely 'egg drop syndrome', however, it is now recommended that full name; egg drop syndrome '76 (EDS '76) should be used to distinguish the name discrepancy from the recent identified disease in duck caused by flavivirus. EDS '76 was first identified in Netherlands in 1974 and the virus was first isolated in Northern Ireland in 1976. It became a problem in European countries such as Ireland, Holland, France, and the United Kingdom. Other places which have had outbreaks include India, Bangladesh, South America, Indonesia, Japan, and Africa. Since then, EDS '76 has been recognised as a global threat for the breeding and laying companies. EDS '76 is caused by double stranded-DNA virus, called Duck Atadenovirus A (formerly knows as Duck Adenovirus A). The diameter of the virus is between 70 to 80 nm by negative staining. The other name of this virus may include duck adenovirus 1 (DAdV-1), EDS '76 virus (EDSV) and adenovirus 127 (AV-127) . The natural host of Duck atadenovirus A are wild and/or domestic waterfowls such as ducks and geese. However, the virus can also infect other bird species through contaminated vaccines, and contaminated drinking water by droppings. Moreover, the virus become apparent and more susceptible in chickens of all ages and breeds, especially broilers and brown egg layers. The virus also causes symptoms in Japanese quails (Coturnix coturnix japonica) and turkeys. Duck atadenovirus A can be transmitted vertically (from hens to chicks). The virus is often latent until the chicks reach maturity. Thereafter, the matured chickens begin to excrete virus and transmit through the eggs and droppings. The virus is also transmitted horizontally between chickens. Mainly, it is seen in commercial egg layers whereby contaminated egg trays are often reused. The virus can survive both inside the eggs and on the eggshell. The virus can migrate from the eggshell to the tray and back to the other eggs placed in the same tray. Contaminated water supply with droppings and litters of the natural host contributes to the horizontal spread as well .