This study was conducted to compare the changes in the bursal and body weights in commercial Isa brown cockerels vaccinated with a live and two killed infectious bursal disease (IBD) vaccines. Two hundred and eighty, day old chicks were divided into four groups of seventy chicks each. Group 1, 2 and 3 were vaccinated with the live vaccine, killed vaccine (A) and killed vaccine (B), respectively, while group 4 was not vaccinated. Vaccination was conducted at 9 and 16 days of age. Five chicks from each group were sacrificed weekly from 2 to 37 days of age and the bursa to body weight ratio (BBWR) were determined. Twenty chicks from each group were challenged with a very virulent infectious bursal disease virus (vvIBDV) at 30 days of age. There was no significant difference in body weight in chicks vaccinated with the live and killed IBD vaccines but there was a significant decrease in the bursal body weight ratio of chicks in vaccinated with live vaccine at p value of 0.0001 and after challenge at p value of 0.0002. Histopathology lesion scoring (HLS) performed weekly from 2 to 37 days of age revealed that there was no significant difference in the histopathology lesions of all the chicks in all groups from day 2 to day 16 of age. From 23 to 37 days of age there was significant increase in the histopathology lesions in group 1 as compared to other groups and control at p value of 0.0001. In conclusion, the live vaccine caused bursal atrophy. Killed vaccine A and B did not have any adverse effect on the BF. Killed vaccines produced from intermediate plus strains of viruses are recommended for the control of IBD in Nigeria and the potential of live vaccines to cause immunosuppression should be investigated.
Infectious bursal disease, live vaccine, killed vaccine, body weight, bursal body weight ratio, histopathogy