Six decades of infectious bursal disease in poultry: The journey so far and challenges ahead
Despite six decades of concerted efforts, Infectious bursal disease (IBD) still remains a major threat to the poultry industry worldwide. Most importantly, the emergence of variant and very virulent strains of infectious bursal disease virus (IBDV) has dramatically changed the epidemiology of the disease, thus resulting in the renewed efforts in the search for effective control measures. Currently, live attenuated, inactivated, and immune-complex vaccines are among the immune-therapeutic approaches employed for the control of IBD in the field alongside adequate biosecurity, albeit with various degrees of success and limitations. Progress in genetic engineering has allowed the generation of reverse genetic IBDV mutants, recombinant live viral vectors expressing the IBDV VP2 immunodominant protein, intra-serotypic recombinant IBDV viral-like particle co-expressing the outer capsid protein structures derived from 2 or more serotype 1 strains or the incorporation of either VP2 or VP2-4-3 polyprotein sequences alongside molecular adjuvants that can be used as IBD vaccine candidates to elicit an immune response. However, despite these advances, outbreaks are still reported even in flocks that have up to date vaccination records and somewhat excellent management practices. This paper reviews aspect of genetic characteristics of IBDV and reflects on the progress and future challenges in providing effective IBD vaccine to achieve effective control of both classical and very-virulent IBDV serotypes that constitute a major devastation to poultry production and health.