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The Thai Journal of Veterinary Medicine

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.

First Page

603

Last Page

611

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