Comparision of Two Different Vaccination Shedule for Fight with Infectious Bursal Disease in Layer Hens

Infectious Bursal Disease Virus (IBDV) is one of the most important immunosuppressive diseases of poultry which classified in Avibirnavirus genus belonging to Birnaviridae family. In this study, two different vaccination schedules were compared in the aspect of protectivity. For this purpose, blood serum samples was collected from 6 flocks of layer chickens in the postnatal period on days 0, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70. Samples were randomly selected from 10 chicks in every sampling. Flock 1 was sampled two more times due to acute clinical infection. The total of 680 serum samples was tested for IBDV specific Antibody (Ab) presence and titers using ELISA. Maternal derived antibody (MDA) was found to be protective for 6-8 days. Standard vaccination schedule (one inactive and three live intermediate vaccines) was carried out at three flocks (2, 3 and 5). In other flocks, one live, one inactive and additional more live vaccine were administered to the chicks into water. Despite regular vaccination, IBD epidemic was seen in flocks 1 and 2. In flock 1, an outbreak was reported with 23% mortality in previous breeding period. This proportion was reduced to 4.5% in this enterprise by applying initially live vaccine, and then any sign of clinical infection has not been detected. Antibody titers were entered augmentation trend in flocks 1 and 2 until day 21. probably due to viral load, this turning point was detected on day 14 in other flocks. Statistical analysis clearly showed that MDA titers showed a sharp decrease in the initially live vaccine given flock. In conclusion, to stimulate cellular immune response using initial live dose as soon as possible is more influential. It means, changing standard vaccination schedule was found to be more effective on protection of animals in the critical period of infection, especially in the presence of viral load in the field.