The percentage infection rate, worm burden and worm recovery rate in mice increased with an increase in the duration of exposure to cercariae. However, mice exposed to cercariae for 4 min had the same worm burden and worm recovery rates as those exposed for 16 min. Mice exposed to 80 and 160 cercariae each exhibited the highest percentage infection rates. The worm burden was highest in mice exposed to 160 cercariae each, while the worm recovery rate was highest in those exposed to 80 cercariae per mouse.