Class II genotype VII Newcastle disease viruses (NDV) are predominant in the Middle East and Asia despite intensive vaccination programs using conventional live and inactivated NDV vaccines. In this study, the protective efficacies of three commercial vaccine regimes involving genotype II NDV, recombinant genotype VII NDV-matched, and an autogenous velogenic NDV genotype VII vaccine were evaluated against challenge with velogenic NDV genotype VII (accession number MG029120). Three vaccination regimes were applied as follows: group-1 received inactivated genotype II, group-2 received inactivated recombinant genotype VII NDV-matched, and group-3 received velogenic inactivated autogenous NDV genotype VII vaccines given on day 7; for the live vaccine doses, each group received the same live genotype II vaccine. The birds in all of the groups were challenged with NDV genotype VII, which was applied on day 28. Protection by the three regimes was evaluated after infection based on mortality rate, clinical signs, gross lesions, virus shedding, seroconversion, and microscopic changes. The results showed that these three vaccination regimes partially protected commercial broilers (73%, 86%, 97%, respectively, vs. 8.6% in non-vaccinated challenged and 0% in non-vaccinated non-challenged birds) against mortality at 10 days post-challenge (dpc). Using inactivated vaccines significantly reduced the virus shedding at the level of the number of shedders and the amount of virus that was shed in all vaccinated groups (G1-3) compared to in the non-vaccinated group (G-4). In conclusion, using closely genotype-matched vaccines (NDV-GVII) provided higher protection than using vaccines that were not closely genotype-matched and non-genotype-matched. The vaccine seeds that were closely related to genotype VII.1.1 provided higher protection against challenge against this genotype since it circulates in the Middle East region. Updating vaccine seeds with recent and closely related isolates provides higher protection.

Genotype VII Newcastle disease viruses (NDV) are still circulating in Egypt despite extensive vaccination programs. In our study, we evaluate the protective efficacy of commercial (HVT- ND) vector vaccine against velogenic NDV Genotype VII.1.1 challenge in broiler chickens. Five vaccination strategies were established; G1 vaccinated by HVT-ND vaccine, G2 vaccinated by HVT-ND and 2 live ND vaccines, G3 vaccinated by HVT-ND, inactivated ND and 2 live ND vaccines, G4 vaccinated by 2 live ND vaccines, G5 vaccinated by inactivated ND and 2 live ND vaccines and G6 Non-vaccinated challenged. All birds were challenged atthe age of 28 days-old. The protection evaluation based on mortality, clinical symptoms, gross pathological lesions, immune response and the mean lesion scores (MLS) of histopathological lesions in brain and trachea at 14 days post challenge. Our findings showed that mortality rates were 26.6 %, 16.6%, 30% and 3.3%, respectively, in G1, G2, G4 and G5, while the best protection was in G3 that did not show any mortality versus 93.3 % in G6. Moreover the MLS on 7dpc were 1.75, 1.6, 1.18, 1.65 and 1.23, in G1, G2, G3, G4 and G5, respectively, while it reached to 2.5 in G6. Results of virus shedding in all vaccinated groups significantly reduced while (G3) also show the more reduction of virus shedding. It could be concluded that full clinical protection against challenge with genotype VII.1.1. NDV can be achieved by co-administrating of HVT-ND, inactivated ND and live ND vaccines as a vaccination program in endemic regions.

Despite extensive vaccinations attempts, genotype VII Newcastle disease viruses (NDV) continue to circulate at the Middle East and Asia causing significant economic losses. In this investigation, we assessed the effectiveness of three inactivated NDV vaccines; genotype II NDV, recombinant genotype VII NDV-matched and laboratory prepared autogenous velogenic NDV genotype VII against challenge by genotype VII velogenic NDV. The following vaccinations were given: group 1(G1) received an inactivated genotype II vaccine, group 2 (G2) received an inactivated recombinant genotype VII NDV-matched vaccine, and group3 (G3) received a velogenic inactivated autogenous NDV genotype VII vaccine. While the live genotype II (Lasota) vaccine was administered to all groups. At the age of 28 days, birds in all vaccination groups were challenged with NDV genotype VII, and protection against infection was assessed based on the mortality number, clinical symptoms, Post mortem lesions, virus shedding, and histological changes. The results of clinical protection were78%, 87% and 96% in vaccinated groups G1, G2 and G3 respectively, against 7 % in the control non-vaccinated challenged group. Virus shedding in all vaccinated groups significantly reduced when compared to the non-vaccinated group (G4). The mean lesion score on 4 and 7 days post challenge were significantly reduced in G3 and G2 compared to G1.In conclusion, more protection against challenge was offered by a velogenic inactivated autogenous NDV genotype VII vaccine that was closely related to genotype VII.1.1 strain than by other vaccines. So we recommended the use of genotype matched vaccine to control NDV in endemic countries.