Partial nucleotide sequencing and phylogenetic analyses of Newcastle disease virus and infectious bursal disease virus isolated in South Korea

The present study was conducted to investigate the genetic profile of two prevalent avian pathogens in Korea namely, Newcastle disease virus(NDV) and infectious bursal disease virus(IBDV). Two farms located in Yeongi-gun, Chungnam were selected for this study. The two viruses were isolated from various organs(spleen, trachea, bursa of Fabricius) of deceased chickens that showed clinical symptoms of Newcastle Disease or Infectious bursal disease like swelling and congestion of the F bursa, facial edema, lacrimation, greenish yellow diarrhea as well as pathological signs like airsacculitis, haemorrhages in the intestines and so on. For analysis of NDV and IBDV, a 466 and 435 base pair fragments corresponding to the HN and VP2 regions which are highly conserved among related strains of NDV and IBDV, respectively, were amplified by RT-PCR and analyzed by sequencing. Comparison of the VP2 region showed a 99.3% homology between the Korean IBDV isolate and the BJ836-attenuated vaccine strain. In contrast, the HN region of the Korean NDV isolate only has an 83 to 84% homology with the vaccine strains LaSota, B1 and VGGA. Our findings reveal that the prevalent NDV strain in Korea is genetically different from the vaccine strains and may explain the recent outbreaks of Newcastle disease in the region.