Molecular characterization of infectious bursal disease virus detected in Morogoro, Tanzania

Abstract

Infectious bursal disease (IBD) virus (IBDV) is a double-stranded RNA virus that belongs to the genus Avibirnavirus of the family Birnaviridae. IBDV is a causative agent of IBD, the highly contagious viral infection of young chickens aged 3 to 6 weeks. IBD outbreaks occur frequently in both vaccinated and non-vaccinated chickens in Tanzania causing significant economic loss among poultry keepers. The control of IBD is mainly done through vaccination, which requires the understanding of molecular and biological characteristics of circulating virus strains in particular geographic location. This study was conducted to determine the genotype of IBDV recovered from confirmed IBD outbreak(s) in 2014 in Morogoro, Tanzania. The investigation was performed by reverse-transcription polymerase chain reaction (RT-PCR), sequencing and phylogeny analysis of nucleotide sequences corresponding to the VP2 hypervariable (VP2-HVR) domain of IBDV. The findings indicated 100% detection rate (n = 10) of IBDV genome from infected bursa of Fabricius samples. Phylogenetic analysis revealed that the sequenced virus belonged to the African very virulent IBDV (VV-IBDV) genotype and was genetically closely related to KZC-109 strain detected in Zambia in 2004. Taken together, our findings suggest that the African VV-IBDV detected in this study was responsible for the IBD outbreak(s) in Morogoro. Further studies are required to examine the transmission dynamics, evolutionary characteristics and antigenicity of field IBDV strains order to design the appropriate control method(s) of IBD in Tanzania and neighboring countries.

Key words: IBDV, VV-IBDV, Sequencing, Phylogeny, Tanzania