Abstract

Background: prolonged immune protection for classic and variant IBV in layer chicken rearing is an important issue.
Objective: evaluation of the protection duration for IBV (M41 and Var2) post vaccination by inactivated combined (H9N2, LaSota, M41 and Var2 IB) vaccine based on laboratory tests and repetition of challenge test.
Methods: : we prepared formalin inactivated combined vaccine for Avian Influenza (H9N2N), Newcastle (La), and IB (M41 and Var 2) by using montanide 71 adjuvant. The prepared vaccine was injected intramuscularly in specific pathogen free and commercial layer chicken, the injection was repeated as a booster vaccination after a month from the first vaccination. Humoral immune response for IBV was measured by ELISA weekly until about one month after the booster vaccination then periodically till the end of duration. Challenge trial for both IB strain was repeated after a month from the first vaccination and after two and six months from the booster vaccination.
Results: The use of formalin inactivated combined H9N2, LaSota and IB (M41 and Var 2) vaccine by using montanide 71 adjuvant via intramuscular vaccination enhanced the immune response as indicated by ELISA for IB, also induced protection until six months after the booster vaccination against challenge with IB (Var 2 and M41) viruses.
Conclusion: Usage of formalin inactivated combined H9N2, LaSota and IB (M41 and Var 2) vaccine with montanide 71 adjuvant can protect chicken until six months from the booster vaccination and decrease shedding of IBV.

Key words: M41, Var2 IB; SPF chicken; layer chicken.