Abstract
Newcastle Disease Virus (NDV) is the causative agent of the most devastating diseases affecting poultry especially in large scale production causing severe economic losses due to high mortality which may reach 100% in very virulent strains of NDV. In the present study, field samples of suspected to be infected by NDV were isolated in Embryonated chicken Eggs (ECEs) of 10 days-old via allantoic cavity for three passages, the isolated virus was identified to be NDV by Haemagglutination inhibition test (HI), electron microscope and reverse transcriptase polymerase chain reaction (RT- PCR). The antiviral effects of both onion and garlic extracts were studied on field isolates and reference strain of NDV. The antiviral effects involve the gross lesions changes of the embryo in inoculated ECEs, Haemagglutination test (HA) and Infectivity test (EID50%). The obtained results showed that most of the isolated viruses expressed subcutaneous Haemorrhage and death of the embryo at the fifth day post inoculation via allantoic cavity at the third passage of ECEs, while the field sample number (10) and the reference strain showed extensive haemorrhage and rapid death of embryos. The isolated viruses were identified to be NDV of the susceptible to be infected samples by HI using hyperimmune serum against NDV prepared in rabbit. The Mean Death Time (MDT) was calculated for the field sample number (10) and the reference strain which showed that the tested samples are velogenic strains. Electron microscopy investigation of some selected samples (of high HA titers) identified the virus as pleomorphic in shape. Some selected samples were analyzed by RT-PCR and gel electrophoresis expressing clear bands using primers against the F-gene of NDV. RT-PCR is considered as the most useful, reliable and accuret laboratory test for confirming field NDV. Brown leaves of onion (Allium Cepa) and bulbs of garlic (Allium sativum) were separately extracted and the extracts were tested for their antiviral activity against the previously isolated and identified NDV. Investigating the antiviral effects of both onion and garlic extracts on some field samples showed absence of virus activity after treatments by extracts, while samples number (10) and reference strain showed reduction of virus in HA test, subcutaneous hemorrhage and EID50%. The reduction of NDV infectivity may be due to the blocking of the attachment of the virus with the cell receptors.

Key words: Newcastle disease, Embryonated chicken eggs, HI, Electron microscope, RT-PCR, antiviral effect, garlic extract, onion extract, EID