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Efficacy of vHVT-ND vaccines administered to day-old turkey chicks against velogenic Newcastle challenge at 28 days of age

Boehringer Ingelheim abstracts presented at AAAP 2021

In the recent years, recombinant vaccines using Herpesvirus of Turkeys as vector expressing the F protein of the NDV (vHVT-ND) were developed and they arecommonly used to protect poultry flocks against velogenic Newcastle Disease (ND) worldwide.

The efficacy of vHVT-ND vaccines has been proved in experimental and field trials in chickens. Nevertheless, few information has been published about theirefficacy in turkeys.

The objective of the present study was to evaluate the efficacy of 2 commercial vHVT-ND vaccines administered by subcutaneous (SQ) route to day-old turkey chicks. The study also examined the vaccine virus replication profile in spleen and feather pulps and compared the serological profiles for Newcastle Diseaseantibodies.

90 conventional day-old turkey chicks were divided into 3 groups; Group 1 received one SQ dose of the vHVT-ND A, group 2 received vHVT-ND Bsubcutaneously and group 3 vHVT-ND A subcutaneously in combination with onedose of live attenuated ND vaccine by eye drop. Spleens and feather pulps were collected on FTA card and analysed by qPCR for HVT virus at 7, 21 and 28 days post vaccination in order to monitor the replication profiles of the vaccines. Blood samples were collected and antibodies were titrated at different ages for vaccine monitoring by different serological techniques. Finally, in order to evaluate the efficacy, a velogenic ND challenge (Herts 33 strain) was performed by oculo-nasal route at 28 days of age.

The results clearly showed that both vHVT-ND vaccines were effective in protecting the turkeys against velogenic ND challenge and reducing the viral shedding. The best results in respect to protection and reduction of viral shedding were obtained by the association of the vHVT-ND with a live attenuated ND vaccine.