In commercial poultry, the Infectious Bronchitis virus (IBV) is a major trigger for economic losses worldwide, causing respiratory issues in broilers and negatively impacting egg production in layers.
Although vaccination has proven to be a crucial tool to combat this threatening disease, the ever-changing nature of IBV strains makes it challenging to achieve effective control of emerging variants, such as QX-like. In this research, we aimed to evaluate the effectiveness of 2 live attenuated vaccines, IB VAR 2 and IB H120, orally administered in specific-pathogen-free (SPF) layer chickens against a virulent strain of IBV known as QX.
A group of 150 SPF chickens was divided into 5 different treatment groups. Three groups received a specific vaccination regime and were exposed to a challenge infection with the IBV-QX strain on day 28.
*Vaccines: IB VAR 2 and IB H120
*Challenge route: orally
*Challenge strain: QX strain (2022 European isolate)
*Challenge dose: 4 Log10 EID50 / bird
*Metrics: ELISA and HI titers, lesion score, viral shedding.
We analysed the birds’ immune responses using ELISA and Hemagglutination inhibition (HI) testing. Both testing methods demonstrated that all vaccinated groups developed specific antibodies for the QX strain. The T03 and T04 groups exhibited the highest antibody titers, indicating a robust immune response against IBV-QX.
Tracheal histopathology scores were measured to evaluate the condition of the chickens’ respiratory tracts. The group that received a combination of IB VAR 2 and IB H120 vaccines on day zero, with a IB H120 booster on day 14 (T05), showed the lowest histopathology scores. This indicates strong protection against natural infections caused by IBV-QX.
Additionally, the viral load from tracheal swabs was assessed using qPCR to measure viral shedding after challenge. The results showed a clear reduction in viral replication in all vaccinated groups. The T04 group had the lowest viral shedding, indicating the most effective reduction of viral transmission.
In the present study, we found that a vaccination regime combining IB VAR 2 and Mevac IB H120 is highly effective in protecting chickens against challenge with IBV-QX strain. Both vaccines can be safely administered to day-old chicks, thus triggering a strong local and systemic immunity that reduces viral shedding and minimizes the risk of horizontal transmission.
To learn more about vaccination against Infectious Bronchitis, please visit:
*2025 Respiratory Integrity Forum
*Webinar ‘Respiratory Integrity forum’ – Educational Series by Kemin Biologics
*Video resources for empowering immune resilience | Kemin EMENA
Source: Email/GFMM
Comment Now