A systematic field study was undertaken on the outbreaks of infectious bursal disease (IBD) during the period from June 2010 to May 2011 in commercial broiler farms of Bangladesh (562) and China (89). Overall prevalence due to the disease was recorded as 12.13 and 7.11% for Bangladesh and China, respectively, and mortality rate was 5.25 and 2.42% for Bangladesh and China, respectively. Dullness, depression, anorexia, ruffled feathers, inability to move and yellowish white diarrhea were observed in almost all the IBD-affected flocks. At necropsy, the gross lesions were observed mainly in the bursa of Fabricius followed by changes in thigh and breast muscles. Outbreaks of the disease were recorded throughout the year. Seasonal influence of IBD showed a significantly (P<0.05) higher prevalence 13.47% and mortality rate 7.73% in winter season in Bangladesh. On the other hand, in China, significantly higher prevalence 6.53% and mortality rate 3.16% was found in summer season. Significantly higher prevalence and mortality rate was observed in the young birds (≤5 weeks of age) than older birds in both the countries. The outbreak of IBD was also found in vaccinated birds (P<0.05) of the two countries. The findings of the study indicated the difference of occurrence of IBD in Bangladesh and China, thereby would help to develop appropriate control strategies for both the countries.

Key words: Chicken, Infectious Bursal Disease, Mortality rate, Prevalence