Isolation and Molecular Identification of Egg Drop Syndrome 1976 (EDS-76) Virus in Egypt

To evaluate the current situation of infection with egg drop syndrome 1976 (EDS-76) virus in Egypt, a total of 35 field samples (15 kidneys, 16 oviducts and 4 oviduct swabs) were collected from 10 EDS-vaccinated layer chicken flocks raised in Menoufia, El-Behera and Gharbia governorates during the period 2014-2015. The flocks showed a decreased laying performance associated with the production of soft-shelled eggs. Virus isolation was attempted in 11-day-old embryonated duck eggs via allantoic sac inoculation. Five days after inoculation, the allantoic fluids were tested for the presence of hemagglutinating (HA) activity using chicken erythrocytes. Seven samples were tested positive for HA activity throughout three consecutive passages. The presence of EDS-76 virus was assessed in all HA-positive allantoic fluids by hexon gene-based conventional and real-time polymerase chain reaction (PCR) assays. In 6 (85.7%) out of 7 samples, PCR was successfully applied to detect the virus DNA, meanwhile all the employed samples were tested positive for the presence of EDS-76 virus by real-time PCR assay. The SYBR green-based real-time PCR assay described in the present study was found to be more sensitive and less time consuming than conventional PCR assay for detection of EDS-76 virus genome.