Protection And Immune Responses Against Virulent Infectious Bronchitis (IB) Viruses In Herpesvirus Turkey - Infectious Bursal Disease (HVT-IBD) Vaccinated Broiler Chicks

Lemiere Stephane, Wilkins Matthew, Forrester Anne, Jones Richard & Ganapathy Kannan | XVII WVPA Congress Cancun | 2011 

 

This paper evaluates the performance of broiler chicks that were vaccinated with two different IBD vaccines, i) HVT-IBD vector vaccine, ii) IBD-complex used as the control vaccine. Broiler chicks were divided to 3 groups in the hatchery; the first group was kept unvaccinated, the second and third groups were subcutaneously vaccinated with HVT-IBD vector vaccine or control vaccine respectively. One of each HVT-IBD vector vaccine and control vaccine respectively. One of each HVT-IBD vector vaccine and control vaccine groups was vaccinated with IB Mass H120 at day old and later with IB virus CR88 at 13 days old. The other group from each of the IBD-vaccinated groups remained as controls. At 7, 14, 21, 28, 35 and 42 days post vaccination, blood was collected for sera (for IBD and IB serology) and 5 chicks from each group sacrificed to determine bursa:body weight ratio (b/bw). In addition tissues of tracheas, lungs, kidneys, cæcal tonsil and rectum were collected for detection of IB virus by RT-PCR. At 35 days post vaccination, 10 chicks from each group were challenged with virulent M41 or virulent IB QX strain KG3P. Five days later, 5 chicks were euthanized for ciliary score and another 5 for collection of various tissues. Bursa integrity as determined by b/bw ratio was used to measure the HVT-IBD vector vaccine efficacy. No difference in terms of clinical protection against respective IB virus challenges was evidenced, nor was a difference in post-IB vaccine application. The main finding was a decreased dissemination of the M41 virulent virus in tracheas of challenged birds with protected bursas, as well as a decreased dissemination of the QX virulent virus in kidneys of challenged birds with protected bursas, demonstrating the benefit of getting bursa integrity after the HVT-IBD vector vaccine application. 

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