In recent years very virulent (VV) IBDV strains and classical (CV) IBDV strains re-emerged and caused devastating outbreaks in different parts of the world. In this study, genetic evolution of fifteen IBDVs collected in Senegal in 1979, 1999, 2007, 2012, 2013 and 2014 was characterized to gain information for a better control of IBD. Following RT-PCR, nucleotide sequence of the VP2 hypervariable region was determined and compared with sequences available in GenBank. Phylogenetic analysis showed that the viruses diverged into two genotypes: Very virulent (VV) IBDV and classical virulent (CV) IBDV. The Senegalese field strains of the first genotype (VV) IBDV had 98.9 to 100% identity among themselves, whereas their identity with reported Nigerian (VV) IBDVs ranged between 96.7 and 99%. The close phylogenetic relationship of the Senegalese and Nigerian strains suggests that they likely derived from a common ancestor. In the phylogenetic tree, all the Senegalese (VV) IBDV strains belonged to the African very virulent types (VV2). The genotyping of senegalese field IBDV strains indicated that the majority of viruses circulating in Senegal are (VV) IBDVs and highlights a genetic stability.
Key words: Infectious bursal disease, phylogenetic analysis, Senegal.