Diagnosis of Clinical Cases of Infectious Bursal Disease Using a Modified Rapid Taq Man-MGB Real-Time RT-PCR Assay

Infectious bursal disease (IBD) is an important contagious viral infection of immune system of poultry. This infection possesses a permanent threat to the profitability of poultry industry worldwide. The aim of this work was to modify the Taq Man-MGB real-time reverse transcription-polymerase chain reaction (rRT-PCR) in one step involving two fluorogenic Taq Man labeled probe and using this protocol for detection of infectious bursal disease virus (IBDV) collected from suspected cases distributed in different regions of the country during the period 2013-2016. The intralaboratory validation of modified method was realized for specificity, linearity, repeatability, sensitivity and reproducibility. It allowed reducing the test running time by six folds. This method was applied on 102 pools of bursa of fabricius (BF) samples collected from affected broiler farms suspected to be infected by IBDV. Birds showing macroscopic lesions including muscle petechial hemorrhages, hypertrophy and hemorrhage of BF, were subjected to molecular analysis using modified protocol “Taq Man-MGB rRT-PCR”. The validation satisfied all criteria and the assay developed could be a useful tool for a very rapid diagnosis of IBDV and permit to detect and to discriminate in one-step very virulent (vv) from non-vv (classic and variant) IBDV strains. Out of 84 IBDV positive samples, a prevalence of 39% for vv strains and 61% for classical strains was noted. These results indicate that despite the vaccination against IBDV, the vv form of this pathologie continues to cause serious problems for Moroccan broiler chickens. The obtained results indicate the successfully detection of IBDV and differentiated all vvIBDV strains from non-vvIBDV strains; Avian infectious agent RNA viruses tested are negative, demonstrating great specificity of the assay. The results obtained indicate that this method is suitable as a routine laboratory test for the rapid detection and differentiation of IBDV strains in samples of avian origin.