Dr. Teshale Sori, Dr. Fufa AbunnaSamson, Terefe2018-11-292023-11-082018-11-292023-11-082017-06http://etd.aau.edu.et/handle/123456789/14658MSc ThesisIn spite of the intensive and varied vaccination procedures to control Infectious Bursa Disease (IBD), the emergence of a very virulent (vv) IBD pathotype in Ethiopia and post vaccination outbreak have led to high economic losses in the poultry industry. The objectives of this study was to determine optimal time of vaccination against IBD and molecular diagnosis of clinical cases in commercial poultry farms in central Ethiopia. The study was conducted from November 2016 to April 2017 on exotic breed chickens kept under semi-intensive and intensive poultry farms selected randomly by simple random sampling technique in Addis Ababa, Bishoftu, and Adama areas. It was a type of prospective longitudinal study where chickens were followed for a defined period of time until they reached 6 weeks of age for clinical cases. A total of 11 samples from 11 farms were collected from clinical cases of infectious bursal diease in chickens (5 samples from Bishoftu, 3 samples from Adama and 3 samples from Addis Ababa) were analyzed with RT-PCR. Of these 8 samples (72.73%; CI: 39.03 – 93.98) were positive for infectious bursal disease virus RNA. The RNA of IBDV was detected in 4 of 5 (80%) of samples from Bishoftu and 2 of 3 (66.67%) of samples from each of Adama and Addis Ababa. For vaccine experimental study, One hundred eighty, day-old Lohman brown chicks were reared and used for this purpose. The chicks were divided into three groups A, B, C. Groups A were vaccinated via drinking water route at 7th day whereas B were vaccinated at 14th day of age. Group C was acted as control. Blood samples were collected from wing vein of individual chicken at day 1, 7, 14, 21, 28, 40 and serum was harvested. Indirect Enzyme Linked Immunosorbent Assay (IELISA) was employed to measure antibody titration. The proportion of chicks in the unvaccinated group with S/P ratio greater than the protective level continuously fall from 0.90 on day 1 to 0.0 on day 14. At day 21 of age after hatching, the time IBD commonly occurred, 55% of the chicks in group A had protective antibody level with average antibody titre of 1064.61± 748.1621; whereas only 5% of the chicks in group B had protective antibody level with average antibody titre of 123.2321 ± 212.0105. It was concluded that in chickens with low MDA, the 1st vaccination should be given at 7th day and repeat after one week. The effect of vaccination programs on the immune response to IBD vaccine in the farms should be further investigated.enCommercial farmsIBDMDAPCRPoultryVaccineThesis