Survey to Detect Very Virulent Infectious Bursal Disease in Broiler Flocks Before Vaccination

This study was conducted to detect the infection with infectious bursal disease virus (IBDV )in broiler flocks before vaccination in Tehran provience . Ten birds of 10 to 12 days olds from each 25 boiler flocks were selected .The mean bursal indexes of all flocks were determined. To detect IBDV genome in bursal samples a RT – PCR test targeting a 643 base pairs segment in VP2 gene were conducted. Two flocks( samples 1 and 2) were posiive indicating IBDV infection. For Further indentification of IBDV , the RT-PCR products were incubated to be digested by endonuclease enzyms SacI and SspI respectively. The RT-PCR products of positive samples ( samples 4 and 9) remaind undigested when were incubated with SacI, an indication for non vaccinal viruses. However only the RT-PCR products of sample 9 could be digested by SspI as the RT-PCR of samples 4 remaind undigested. Although the mean bursal indexes of these two infected flocks were less than those of noninfected ones, however only mean bursal indexes of the flock 4 were significantly different from those of non-infected flocks. In conclusion, this study showed that infection of broilers with very virulent pathotype of IBDV is probable before vaccination.