The causal agent of IBD is infectious bursal disease virus (IBDV), a non-enveloped double stranded RNA (dsRNA) virus belonging to the family Birnaviridae (Jackwood et al., 1984).
Various diagnostic methods like indirect haemagglutination (IHA) test, virus neutralization test (VNT), enzyme linked immunosorbent assay (ELISA), fluorescent antibody technique (FAT) and agar gel immunodiffusion test (AGIDT) are used limitedly to detect IBDV and molecular techniques like reverse transcriptase polymerase chain reaction (RT-PCR) have frequently used to detect viruses from the field samples (Gohm et al., 2000; Mathivanan et al., 2004).
The diagnosis of the disease until now has depended mainly on clinical signs, gross pathology, and serological tests, and there has been a lack of information about the molecular detection of IBDV strains in Pakistan.
For isolation of IBD virus, 10 day-old embryonated chicken eggs were inoculated through chorio-allantoic membrane (CAM) at dose rate of 0.2ml of IBDV inoculum having titer of (EID50 105.50/100ul) (0.1 ml virus suspension + 0.1 ml antibiotic mixture).
Out of 35 field samples 28 (80%) were positive for IBDV and all virus isolates were positive for RT-PCR.
This study indicates that IBDV vaccine have detrimental effects, as the FCR value of NDV vaccinated and non-vaccinated control were better (F= 1.9594 and G=1.9386) as compared to the IBDV vaccinated groups.
The groups F (only NDVvaccinated) and G (non-vaccinated control) were better FCR as compared to the groups A, B, C, D and E which were vaccinated with intermediate strain, hot strain and complex IBDV vaccine.