A study on efficacy of live attenuated gumboro vaccine in different ages of broilers

Infectious bursal disease (IBD) is an acute highly contagious viral disease of immature chickens with significant economic importance. Infectious bursal disease virus samples were collected from different poultry farms located at the vicinity of Karachi, and were brought to Sindh Poultry Vaccine Centre, Karachi, for vaccine preparation. Three local strains, A-13-2000, B-18, and L- 2000 of IBD virus were selected to evaluate them as a vaccine strain. The challenge and Agar Gel Precipitation (AGP) test were carried-out and the results revealed that the strains were specie specific, some induced highly prominent lesions only in broiler and some in layers, except the strain B-18, which produced prominent lesions in both broilers and layers. The strain B-18 was selected for vaccine preparation. After preparing of vaccine, experimental trials were carried out to determine its efficacy in different ages of broilers to recommend an effective vaccination programme against the disease. Two hundred, day-old broiler chicks were wing banded for identification and were divided into four groups, i.e. A, B, C and D (control group). The chicks of group A were vaccinated with locally prepared live attenuated Gumboro vaccine at 8 days of age through eye-drop . The chicks of group B were vaccinated at 8 and 15 days and while group C, were vaccinated at 8, 15, and 23 days of their age. The chicks of group D were kept as a control. Serum samples were collected at a week interval upto six weeks. Antibody titer was determined by using the Agar Gel Precipitation (AGP) test technique. The results revealed that the chicks administered with live IBDV vaccine at 8 days and subsequent two booster doses at a week interval (group C) produced significantly higher antibody titer, while some decrease in sera of chicks of group B at 3 weeks post vaccination was recorded. Whereas the chicks of group A showed lower antibody titer but remained constant and no antibodies were determined in control group (D) throughout the experiment. The chicks were challenged after 6 weeks, with a local strain 13-18 of IBDV and lesions were recorded up to 5 days. The challenge results indicated that strong lesions were observed in all the visceral organs of control group (D), whereas, haemorrhagic lesions were also recorded in bursa up to five days post challenge. The chicks of group B showed lesions only in pectoral muscles, while chicks of group C also showed mild lesions during the first two days of post- challenge. No lesions were observed in bursa and other visceral organs as they were observed in control group. Furthermore, no maternal antibodies in the sera of chickens at 1st week of age were found by AGP test.