Accession-level reassessment of cox1 identity in the first Korean case of Echinococcus multilocularis

The first Korean case of Echinococcus multilocularis interpreted the probable origin of the isolate on the basis of cox1 sequence similarity, originally reporting 99.8%-99.9% similarity to Asian isolates and 99.5%-99.6% similarity to European isolates. To examine whether this similarity-based interpretation remains epidemiologically informative, we re-evaluated currently available cox1 sequences with high sequence identity at the accession level. Using AB780998.1 as the query, BLAST hits with ≥99.5% identity were collected, and 110 non-self accessions were manually annotated according to clade classifications reported in the source literature. Sequence alignment and phylogenetic assessment were performed with MAFFT and IQ-TREE. Across the re-evaluated dataset, sequences with identities from 99.5025% to 99.6269% were predominantly classified as European, whereas all sequences from 99.6891% to 100% were classified as Asian. The only 2 exceptions to this overall pattern were OR263180 and OR263183, which were classified as Asian despite falling within the lower identity band. These 2 accessions were reported in a study using a concatenated mitochondrial framework including cox1, cob, and nad2, suggesting that single-marker interpretation may be limited in such borderline cases. In the 1,608 bp alignment, 1,544 sites were constant and only 19 were parsimony-informative. Despite this limited variation, cox1 percent identity showed strong concordance with classification of Asian and European groups reported in the source literature. These findings indicate that high cox1 identity may serve as a practical proxy for broad lineage discrimination between Asian and European groups of E. multilocularis, although rare borderline cases may require confirmation with multiple mitochondrial markers.