We noted in the study of Yoonuan et al. [13] that antibody cross-reactivity of opisthorchiasis, ascariasis and strongyloidiasis also occurs in IgG-ELISA using 35 kDa cathepsin L lacking signal peptide (rPpsCatL, recombinant P. pseudoheterotremus cathepsin L). This evidence concerns the gene CTSL and opisthorchiasis.