Highly virulent strains of the avian infectious bursal disease virus: Literature review and epidemiological situation

This review focuses on the very virulent viral avian infectious bursal disease virus (vvIBDV). This virus was first described in the United States about 30 years ago, it quickly spread around the world, causing considerable economic losses; after three decades, it still poses a threat to the poultry industry. The emergence of acute forms of the disease has radically changed the epidemiology of IBD. Although their origin is still under study, vvIBDV has spread throughout the world in an explosive but conservative manner. This raises the question of the origin of vvIBDV, the possibility of existence of reservoirs and the possible emergence of new distinct lineages in the future. It has become clear that the amino acids in the hyper-variable region of the VP2 viral protein constitute a molecular basis for antigenic variation, but no mutation that determines pathogenicity has been identified. These molecular markers of the vvIBDV strains should be considered more as a common evolution than as markers of virulence. This article presents a synthesis of the molecular, phylogenetic, epidemiological, antigenic and pathotypic characteristics of the very virulent strains of IBDV.

Keywords: Review, vvIBDV, molecular, phylogeny, epidemiology, pathotypes