Chicken embryonal vaccination with avian infectious bronchitis virus

Area of Science:

• Veterinary Virology
• Poultry Immunology
• Vaccine Development

Background:

• Infectious Bronchitis Virus (IBV) poses a significant threat to poultry health.
• Commercial IBV vaccines require optimization for safety and efficacy.
• Marek's disease virus (MDV) is another major concern in poultry vaccination.

Purpose of the Study:

• To attenuate a Massachusetts 41 strain IBV vaccine.
• To evaluate the efficacy and safety of the attenuated IBV in chicks.
• To assess the compatibility of the attenuated IBV with turkey herpesvirus (HVT) in a bivalent vaccine formulation.

Main Methods:

• A commercial IBV vaccine (Massachusetts 41 strain) was passaged 40 times in chicken kidney tissue culture.
• The attenuated virus (P40-IBV) was administered to embryonating chicken eggs (ED 18) and newly hatched chicks.
• Chicks were challenged with virulent IBV and Marek's disease virus (MDV) to assess protection.
• Vaccine compatibility was tested by co-administration with HVT.

Main Results:

• The 40th passage IBV (P40-IBV) was apathogenic for embryonating eggs.
• Chicks from eggs injected with P40-IBV developed antibodies and were protected against virulent IBV challenge.
• P40-IBV provided less protection when administered at hatch compared to ED 18.
• Co-administration of P40-IBV and HVT did not interfere with the efficacy of either vaccine component.

Conclusions:

• Passage 40 of the IBV vaccine renders it safe for embryonating eggs and protective in chicks.
• The attenuated IBV vaccine is most effective when administered during embryonic development (ED 18).
• A bivalent vaccine combining attenuated IBV and HVT is feasible for simultaneous protection against IBV and MDV.