Nucleotide sequences were obtained for the second internal transcribed
spacer of the ribosomal gene repeat and for part
of the mitochondrial cytochrome c oxidase subunit I gene
from geographical isolates of Paragonimus westermani from
Japan, China, Korea, Taiwan, the Philippines, peninsular Malaysia and Thailand.
Sequences were obtained from several
other species of Paragonimus for comparative purposes. Two
groups were recognized within P. westermani: an NE group
(China, Japan, Korea, Taiwan) which was relatively uniform and included
both diploid and triploid forms, and a southern
group (Malaysia, Thailand, Philippines), members of which were genetically
distant from one another. According to both
ITS2 and COI data, genetic distances among P. westermani isolates
equalled or exceeded those between some distinct
species of Paragonimus. The ITS2 sequences were conserved
relative to COI sequences. Substitutions among the latter
may be approaching saturation within the genus Paragonimus.