Efficacy of different vaccination programs of recombinant HVT-NDV vaccine against genotype VII NDV Challenge in broiler chickens

Abstract

This study determined the efficacy of recombinant HVT- NDV ( rHVT- NDV) vaccine simultaneously
vaccinated with live vaccine at 1 day old and a booster vaccination with live vaccine at 10 days old against Asiatic,
Genotype VII NDV in broiler chickens. The chickens were divided into 5 groups. The chickens in groups 1, 2 and 3
were vaccinated with rHVT- NDV vaccine and different live vaccines at 1 day old, and then finally received a booster
vaccination at 10 days old. The chickens in groups 4 and 5 served as the positive and negative control groups,
respectively. The chickens in groups 1, 2, 3 and 4 were challenged with NDV at 14, 21, 28 and 35 days old, 20 chickens
of each group at a time. Clinical signs and mortality were observed for 14 days after each time of challenge. Blood
samples were collected at 1 and 10 days old, on the virus inoculation day and 14 days post- inoculation, to determine
NDV antibodies. Swab samples were collected from the chickens challenged with the virus at 35 days old to detect
NDV RNA by real- time PCR. The results reveal that the protection rate of the vaccinated chickens, which were
challenged at 14 days old was 70- 95%, while the protection rate of all vaccinated groups increased to 90- 100% when
they were challenged at 21, 28 or 35 days old. The vaccinated groups had a lower rate of virus shedding when compared
to the challenged control group. It is concluded that all of the vaccination programs of rHVT-NDV vaccine in this study
could be used to reduce economic loss due to infection by Genotype VII NDV.