Expression of Ov-aep-1 in developmental stages of O. viverrini, as determined by RT-PCR. The following cDNA templates were included: lane 1, egg; lane 2, metacercaria; lane 3, juvenile worm; lane 4, adult worm; lane 5, adult worm cDNA library. The lower panel shows expression of the actin mRNA in the developmental stages, included here as a constitutively expressed control transcript.