In the first study, the emergence pattern of O. viverrini from B. (D.) s. goniomphalos each infected B. (D.) s. goniomphalos was put in a 5.0 × 1.5 cm Petri dish, half-filled with conditioned tap water. The snails were left near a window throughout the experiment, to expose the cercariae recorded. Each snail was cleaned with tissue paper before transfer to a new 5.0 × 1.5 cm Petri dish that changed at every 2-hour interval, from 6:00 AM to 4:00 PM of the next day. Room and water temperatures, and intensity of light (Lux meter DIGICOM LX-150), were recorded every two hours during the experiment.