Праћење имунолошких и патолошких ефеката атенуираних вакцина у имунопрофилакси бројлерских пилића против инфективне болести бурзе / Investigation of immunological and pathological effects of attenuated vaccines in immunoprophylaxis broiler chickens agains

Infectious bursal disease (Gumboro disease) is a contagious viral disease of young chickens. The causative agent is an RNA virus that belongs to the family Birnaviridae. It exhibits tropism toward bursa of Fabricius causing damage to cells and atrophy. The disease is controlled by vaccination of susceptible broiler breeders and chickens. The use of attenuated vaccines may lead to the reduction of certain production parameters. The aim of this study was to prove which of the applied attenuated vaccines, intermediate Gumbokal, Gumbokal D78 and intermediate-plus Gumbokal 228E, induces the best immunological response and leads to fewest damages to burza of Fabricijus tissue and spleen. We tracked whether it influences on immunosuppressive vaccine against Newcastle disease and if it leads to reduce of body mass of broiler chickens. Basic experimental groups were vaccinated on the fourteenth day of age against Gamboro diseases, and sub-groups were formed of the basic experimental groups which have been vaccinated against Newcastle disease in different time periods: O1-1, O2-2, O3-1 after seven days, O1-2 , O2-2, O3-2 after fourteen days, O1-3, O2-3, O3-3 after twenty-one days of vaccination against Gumboro disease. From the first to the fourty second day of the experiment, blood was extracted form the chicks every seven days, their body weight was measured and burza and spleen were sampled. Blood serum were assayed for the amount of the antibody titer by enzyme-linked immunosorbent assay test (ELISA) for Gumboro disease, and with Hemagglutinationinhibition test (HI) for Newcastle disease. The biggest titer for Gamboro disease were showed by experimental group O1, then O2 and group O3 the lowest. In the experimental subgroups O3-1, O3-2 and O3-3 immunosuppressive effect was exhibited on the immune response to Newcastle disease. Relative weight and bursal index were determined for burza of Fabricius to determine whether there was atrophy after administration of the vaccine. The lowest bursal index was established in the experimental group O3, followed by O2 and O1. Such sequence was establilshed also for histopathological changes in the burza. The obtained results indicate that the use of the intermediate-plus vaccine induces the best immune response, but also the lowest relative value of the mass and burzal index, as well as a lower body weight compared to the inermediate vaccine. Applied vaccines did not affect the relative weight of the spleen and have not led to the appearance of histopathological changes in it.