Porcine reproductive and respiratory syndrome virus (PRRSV) is classified into two genotypes, the North American-type (NA-type) and the European-type, and each genotype is also genetically divergent. We determined the ORF5 nucleotide sequences of thirty isolates from various areas in Japan during 1992 and 1993 and during 2000 and 2001. All the isolates belonged to the NA-type. Phylogenetic analysis of the overall NA-type PRRSVs in the world identified at least five major genetic clusters (I, II, III, IV and V). The 1992-1993 Japanese isolates belonged only to clusters I and III, while the 2000-2001 isolates were more divergent. The cluster I PRRSVs, which were found in various areas around the world, were distributed in the western part of Japan. The cluster III PRRSVs, which included 63% (20/32) of the Japanese isolates, one Chinese isolate and one Taiwanese isolate, were mainly found in the eastern part of Japan. These results suggested that cluster III would have evolved locally in Asia. Further study will be focused on whether these genetic variations among the strains affect their antigenicity or pathogenicity.
(Research Team for Viral Diseases, TEL +81-29-838-7763)
Reference:
Yoshii et al. (2005) Arch. Virol. 150:2313-2324.
