SEQUENCE COMPARISONS OF A HIGHLY VIRULENT INFECTIOUS BURSAL DISEASE VIRUS PREVALENT IN JAPAN

Variable cDNA regions in the VP2 gene of five highly virulent infectio us bursal disease viruses (IBDVs) isolated in Japan were amplified by polymerase chain reaction (PCR) and sequenced. The nucleotide sequence s of five highly virulent IBDVs were identical. Comparisons of the nuc leotide and the deduced amino acid sequences with those of other strai ns of IBDV indicated that Japanese highly virulent IBDV is different f rom all other strains of IBDV that were compared. The number of amino acids that differed between strains (substitution score) showed that h ighly virulent IBDV is more closely related to European virulent strai n 52/70 than to Japanese conventional strains. These results strongly suggest that a single strain of highly virulent IBDV that might have o riginated from a European strain is prevalent in Japan.