Effect of age and route of administration on the efficacy of various live infectious bursal disease vaccines in broilers

One hundred and twenty birds were selected and equally divided into 6 groups and coded with A to F. Before administration of vaccines, the birds of different groups except control were tested by ELISA for maternal antibodies and measured as 583 plus minus 632 at day one of age. Group A chicks received its first vaccine of Bursin-706 (an intermediate strain vaccine) at day one of their age through spray followed by two other doses of Bursine plus vaccine (hot strain) at days 12 and 22 in drinking water respectively while, group B chicks' received Bursine-11 (an intermediate strain) at day 1, 12 and 22 of their age through sub-coetaneous inoculation. Whereas, group C chicks was given its initial dose of Bursine Plus vaccine at day 9, followed by another dose of the same vaccine at day 19 of their age. But group D chicks offered got its first vaccine of Bursine Plus at day 12, followed by another dose at day 22 in drinking water. Group E received Bursaplex by subcutaneous inoculation at day 1, and two more doses of Bursine Plus at days 12 and 22 of age in drinking water. Whereas, group F chicks' was left without vaccination and was considered to be a control groups. It was found that the birds received different doses of vaccines through different routes at day one of their age in the presence of maternal antibodies did not induce any antibodies formation as recorded in all groups received vaccines at day 1, 9 or 12 exhibited similar pattern antibody profiles. However an increase in the mean titer of antibodies was recorded from day 17 and onwards. Furthermore, on day 39 of age, the birds of all groups including control were challenged with field strain of IBD virus collected from bursa of' clinically infected chicks. No morbidity and mortality were observed. During present study, some milder infection with field strain of IBDV almost a week ago recorded were also found in the control group when challenged with IBDV . It is concluded that IBD vaccines in the presence of specific maternal antibodies of IBD could not induce antibody formation and one should wait until unless the maternal antibodies decline to level considered being fit for vaccine "intake". It was also concluded that antibodies titer 1500 with live vaccines were protective against the IBDV. It was further observed that two doses of vaccines, one at day 10-12 of age either with an intermediate or hot strain and other at day 22-24 of age with a hot strain will suffice for inducing protective antibodies against IBDV. From the present investigation, it is concluded that IBDV vaccines in the presence of specific maternal antibodies of IBD are not able to induce antibody formation. The administration of vaccines during 2nd week of age clearly demonstrated slow progress in antibody formation but from day 17 onwards, a sharp increase in antibody production was today 31 in the sera of the all vaccinated chicks. It is also concluded from the study the titer 1500 of live IBD vaccines are protective against IBDV infection It is further observed that two doses one at day from 10-12 of their age either with an intermediate or hot strain and other at day from 22-24 of their age with a hot strain induced protective antibodies against IBDV.