Characterisation of New Zealand isolates of infectious bursal disease virus

Isolates of infectious bursal disease virus (IBDV) were obtained from domes tic poultry in New Zealand in 1997 and 1998. An in-vivo pathogenicity study carried out in specific pathogen free (SPF) chickens demonstrated the low virulence of one of the virus isolates. The nucleotide sequences of the hyp ervariable region of the VP2 gene of two isolates were determined and compa red with published sequences of strains from other countries. The deduced a mino acid sequence of the two New Zealand IBDV isolates showed 100% identit y with each other, suggesting that little genetic drift had occurred. Phylo genetic analysis showed that the New Zealand isolates were more closely rel ated to two attenuated IBDV strains (Cu1 and PBG98) than to classical (STC and 52/70), very virulent (DV86), variant (variant E) or Australian (002-73 ) strains. The results support the hypothesis that an attenuated strain of the virus was inadvertently introduced into the NZ poultry population in 19 93.