Nucleotide sequence and polymerase chain reaction/restriction fragment length polymorphism analyses of Aleutian disease virus in ferrets in Japan

Two ferrets with spontaneous Aleutian disease (AD) were found in Japan. The diagnosis was verified by polymerase chain reaction (PCR) amplification of part of the capsid gene specific to AD virus (ADV). The nucleotide sequenc es (365 bp in length) of the amplified fragments from the 2 ferrets differe d by a single nucleotide, producing an amino acid alteration. Compared with other types of ADV, these isolates had 96% sequence similarity to a publis hed ferret ADV (FADV) in contrast to < 91% homology to various types of min k ADV (MADV). The phylogenetic tree of ADVs indicates that these 2 isolates and the published FADV belong to the same genetic group and definitely are divergent from MADVs. The predicted amino acid sequence of the hypervariab le segment in the capsid gene was conserved among the 3 types of FADV. Thes e results indicated that the 2 isolates found in Japan were new DNA types o f FADV and could have been derived from FADV(s). A restriction fragment len gth polymorphism (RFLP) method to distinguish the ferret types of ADV from the mink types of ADV was developed on the basis of differences in their nu cleotide sequences. Digestion of the PCR products with AfaI or Seal provide d different cleavage patterns for FADV and MADV. This PCR/RFLP analysis of the ADV capsid gene will be a valuable asset for diagnosis of this virus in fection in ferrets.