27.06.2025

Animals 2025, 15, 1722

A study published in Animals investigates the effects of various in-ovo vaccination strategies against infectious bursal disease (IBD) on the immune response and histopathological status of broiler chickens. IBD, caused by a highly contagious virus, primarily affects young chickens by damaging the bursa of Fabricius, leading to immunosuppression and increased vulnerability to other diseases. To mitigate these impacts, different types of live vaccines - mild, intermediate, and hot - are employed, with their efficacy and immunosuppressive effects varying depending on the dosage and timing. In this study, four commercial flocks consisting of 120,000 chickens were used, with three groups receiving different IBD vaccines via in-ovo injection on day 18 of incubation, while one group served as unvaccinated controls. After hatching, all vaccinated groups were additionally vaccinated against Newcastle disease (ND) via spray. The researchers evaluated the immune response by measuring antibody titers at multiple time points, and assessed the health of the bursa of Fabricius through histopathological examination and quantification of B lymphocytes.
The vaccination program did not significantly impact the serological response to ND across the groups, indicating that in-ovo vaccination against IBD does not interfere with subsequent ND immunization. Although live immunocomplex IBD vaccines may induce a rapid and robust antibody response, they do so at the expense of bursal integrity and long-term immune competence. The recombinant HVT-VP2 vaccine offers a safer alternative, inducing protective immunity without damaging lymphoid tissue, thus maintaining broader immunological health and performance in broilers.