The development of five schistosome species was compared in mice by the recovery of schistosomula from chopped lung tissue and of adult worms by portal perfusion. Three developmental patterns appeared. (1) Schistosoma japonicum was unique in showing an early establishment of schistosomula in and a rapid departure from the lungs together with the highest worm recovery; (2) S. haematobium contrasted by establishing later and persisting in the lungs for at least 2 weeks while yielding the lowest adult worm recovery; and (3) S. intercalatum, S. mansoni, and S. rodhaini had an intermediate pattern--they resided in the lungs for several days, then disappeared and produced intermediate numbers of adults. Lung petechiae, known to accompany the migration of S. japonicum, were never detected after infection with the other species. We speculate that the three migration patterns of schistosomes are related to the size of the relative spectra of naturally infected definitive hosts.

Vomitus from adults of five Schistosoma species was screened for biochemical homologues of the mammalian cysteine proteinases cathepsins B, H, and L. Bovine cathepsin B and rat cathepsin L served as references. Using the substrate Arg-NMec, a schistosome cathepsin H-like activity was never detected. All species degraded the cathepsin B substrate Z-Arg-Arg-NMec, but distinct species differences were observed with respect to pH optima and buffer preferences. The cathepsin B and L substrate Z-Phe-Arg-NMec was similarly degraded by all species, and activity was abolished by the cysteine proteinase inhibitor E-64. Preferences by vomitus proteinase activities for Z-Phe-Arg-NMec over Z-Arg-Arg-NMec were similar to or higher than those found for bovine cathepsin B but well below those observed for rat cathepsin L; also, the preferential cathepsin L inhibitor Z-Phe-PheCHN2 only partially inhibited proteinolytic activity. The results suggest the possible presence in vomitus of a minor cathepsin L-like activity and demonstrate a major cathepsin B-like activity that is biochemically variable between schistosome species.