So far, very few secreted proteins from trematodes have been characterized, although their role in the mechanisms that allow the parasite to escape host's immune response have been largely documented. Here we performed a proteomic analysis of excretory-secretory proteins from the intra-molluscan larval stages of Fasciola hepatica. We identified two antioxidative enzymes: a Cu/Zn-superoxide dismutase (Cu/Zn SOD) and a thioredoxin (TRX) previously characterized in ES products from adult stages. These results support the importance of parasite detoxication of reactive oxygen species in invertebrate hosts, and raise the question of the possible conservation of major immune evasion effectors across trematode developmental life-stages.