Efficacy of VAXXITEK® HVT+IBD Vector Vaccine Against Early And Late Hypervirulent Infectious Bursal Disease Challenges, In Presence Of Maternal Antibodies And In Comparison To A Live IBD Vaccine In Complex With Antibodies
Le-Gros F.X., Jay M.L., Bizzini S., & Goutebroze S. | 16th WVPAC Marrakesh | 2009
Two technologies are currently available in broiler production to allow in ovo or one-day- old vaccination against Infectious Bursal Disease (IBD) in presence of maternal antibodies: the use of an HVT-IBD vector vaccine or the use of a live IBD vaccine (strain Winterfield 2512) in complex with antibodies. This trial aimed at comparing their relative efficacy against a hypervirulent challenge (French isolate AFSSA 91-168) 21 and 42 days post vaccination. 150 commercial broiler eggs were incubated for 18 days. 2 groups of 60 embryonated eggs were then vaccinated in ovo using an adapted mechanic device. They respectively received (G1) 1 dose of an HVT-IBD vector vaccine (Merial S.A.S., VAXXITEK HVT+IBD) or (G2) one dose of the IBD strain Winterfield 2512 in complex with antibodies in a volume of 50L. A third group of 30 eggs (G3) remained unvaccinated. The eggs were then hatched and the respective chicks placed in three corresponding groups in isolation units. These groups were then divided in 3 subgroups of at least 10 birds: subgroup A to be challenged at day D21; subgroup B to be challenged at D42, subgroup C as vaccinated-unchallenged controls (with the exception of G3). Blood samples were taken from these groups at D0, D21 and D42 to be tested for IBD antibodies using the Elisa test ProFLOK Plus IBD (Synbiotics Corporation, USA).The IBD challenge was performed by ocular inoculation with 4.3 log10 EID50 of the vvIBD strain 91-168. The birds were observed 10 days post challenge for mortality or clinical signs and then sacrificed for post mortem observations. They included the bursa/body weight ratio and macroscopic and histological examination of the bursa of Fabricius.
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