Adult-worm burden were assessed in two different experiments (Exp. 1 and Exp. 2). Columns: open; challenge control mice; hatched, adjuvant-treated control mice; solid, calpain-immunized mice; dotted, mice immunized with irradiated cercariae. A significant worm burden difference was found between calpain-immunized mice and adjuvant-treated controls (36.7% reduction in experiment 1 and 41.2% reduction in experiment 2). ∗, P < 0.05; ∗∗, P < 0.01. SD, standard deviation.