Molecular characterization of infectious bursal disease virus field isolates from selected areas of Ethiopia and sequence based comparison with currently used vaccine strains
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2019-06
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Abstract
Matching of field isolates of infectious bursal disease viruses with vaccine strains is an important pre-requisite for production of effective vaccine. In this study isolation and characterization of infectious bursal disease virus was done from outbreaks reported from commercial poultry farms with the objective of investigation of the degree of genetic similarity between virulent viruses isolated from outbreaks and commercially available vaccines. Bursa samples were collected in pools from chickens affected by outbreaks for virus isolation. Isolation of the virus was done using chicken embryo fibroblast cell lines designated DF-1. Identification of the strains of the infectious bursal disease virus was carried out using reverse transcriptase polymerase chain reaction targeting VP2 gene of infectious bursal disease virus. The genetic similarity among the field strains and vaccine strains was performed by comparing the deduced amino acid differences at positions 222, 242, 256, 294 and 299. Nine outbreaks affecting 30250 chickens were investigated. All of the pooled samples collected from outbreaks and cultured yielded positive results. Molecular analysis confirmed that the viruses isolated were infectious bursal disease virus. Further sequence analysis revealed that the infectious bursal disease viruses isolated were all very virulent strains. The deduced amino acid sequence analysis showed that the virulent isolates reported in this study are more similar to European strains such as UK661 and DV86 than the vaccine strains used in Ethiopia. This study has showed that very virulent IBDV strains are circulating in the country affecting commercial poultry farms and distribution centers. Therefore, the veterinary and livestock authorities should take this into account.
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Commercial poultry farms, Filed strains, Infectious bursal disease