comparison of pathogenicity and serologic response of four commercial infectious bursal disease live vaccines.

various commercial vaccines for immunization of broiler chickens against infectious bursal disease (ibd) are available, so it would be appropriate to compare the pathogenicity and immune response of chickens to these vaccines. in this study the pathogenicity and serologic response of four ibd vaccines, cloned d78®, bursine-2®, bursimune® and cevac gambo-l®, were evaluated in specific pathogen free (spf) chickens. 100 spf chicken were divided into five equal groups (one control group and four vaccinated groups) kept in isolator units and vaccinated at 16-day-old via the eye-drop route. at 5, 10 and 20 day post vaccination birds from each group were weighted, bled, and then necropsied. lesions were recorded and the bursa of fabricius was taken out, weighted and was fixed in 10% neutral buffered formalin and processed for histopathological examination. the pathogenicity and serologic effects of the ibd vaccines were evaluated by the antibody response, the bursa, spleen and thymus/body weight ratios and histopathological lesions of the bursa. no any clinical signs and mortality was observed in all groups. the results of this study indicate that d78 and gambo-l vaccines showed to be more pathogenic and caused more severe bursal damages and also induced higher elisa titers in serological evaluation.