Genetic characteristics of virion protein 2 genes of infectious bursal disease viruses isolated from commercial chickens with clinical disease in South Korea.

We examined the molecular identification of 13 infectious bursal disease virus (IBDV) strains isolated in Korea from January 2009 to January 2010. Sequence analysis of the variable virion protein 2 gene suggested that 3 of the isolates were very virulent IBDV, 8 of the isolates were classical virulent IBDV, 1 of the isolates was antigenic variant IBDV, and 1 of the isolates was intermediate plus vaccine strain. However, the clinical effects were evident for these strains regardless of classification because each chick flock was raised in various field situations with a different vaccine program and complications by other viruses or bacteria. Therefore, our observations revealed that IBDV strains of 4 genotypes, including vaccine strain, were recently present in South Korea and that the IBDV strains need to be discriminated using genetic characterization of virion protein 2 gene for efficient diagnosis and disease control.