Genetic Analysis of Infectious Bursal Disease Virus (IBDV) from a Farm in Vom, Plateau State, Nigeria

This study describes the genetic analysis of an atypical infectious bursal disease virus (IBDV) detected from an outbreak in a poultry farm in Vom, Plateau State, Nigeria in 2017. The farm with seven thousand, six hundred and eleven (7,611) four weeks old vaccinated pullets had 76.2% mortality (5,796 dead birds) as a result of the outbreak. Thirty-two bursae of Fabricius samples showing lesions of IBD were aseptically collected for IBDV antigen detection and molecular characterisation. All the tested samples were positive by the agar-gel immunodiffusion test (AGDT) for IBDV antigen while the VP2 gene could be detected in 60% of these samples by polymerase chain reaction (PCR). One PCR positive sample was sequenced. Nucleotide and deduced amino acid sequences obtained were compared to sequences from GenBank. The IBDV strain detected (IBDV/VOM/NG/2017) was distinct from the attenuated vaccine strain used on the farm, but formed cluster in the very virulent (vv) IBDV group in the VV2-1 subcluster and was most closely related to previously published IBDV strains from Nigeria (Plateau 104/NG/2010, and more recently Bauchi127/NG/2014) with 98% nucleotide identity. Substitution mutations were observed across the VP2 region of the recent vvIBDV strain detected. This finding provides an update on the epidemiology and molecular dynamics of IBDV in Nigeria with implications for control.