Investigation of vaccine efficacy and potential vaccine genotypes in different vaccination strategies against Gumboro disease in laying hens

Infectious bursal disease, or Gumboro disease, is a viral infection that causes serious economic losses in the poultry industry. The infection has been reported in countries with developed poultry industries in Europe, America, Africa, Australia, and Asia. Epidemiological studies have shown that variant and reassortant strains have begun to dominate over the years. The virus causes malformations in the bursa Fabricius and lymphocytes, which are important components of the immune system in poultry, leading to suppression of the immune system and rendering infected animals susceptible to pathogens. Vaccination programs are being conducted worldwide to control infectious bursal disease. However, a single, definitive vaccination strategy has not yet been reported. The aim of the present thesis study is to diagnose the Infectious Bursal Disease Virus, which causes Gumboro disease, using Reverse Transcriptase Polymerase Chain Reaction (=RT-PCR), to amplify the VP-2 gene of the virus using RT-PCR and perform sequence and phylogenetic analyses, to compare the genes of IBDV viruses found in our country and other countries, to conduct isolation studies on the identified Very Virulent Infectious Bursal Disease Virus (=vvIBDV) strains and to identify potential vaccine strains. In the RT-PCR analyses conducted in the study, 33 of the 70 samples examined were found to be positive. Positive results were obtained in 50% of samples from the Marmara Region, 60% from the Aegean Region, and 25% from the Central Anatolia Region. In addition, serum samples collected from farms were compared to determine the antibody response to different vaccines, and seropositivity was detected in all of these serum samples. As a result of phylogenetic analyses, three farms were found to be in the same group as the reference vaccine strains, in line with the vaccine applications carried out. One farm showed similarity to the vvIBDV reference strains. Another farm showed similarity to a vaccine strain different from the applied vaccine strain.