Comparison of the Protective Efficacy on Mekongi Schistosomiasis in Mice Induced by Antigens Derived from Cercariae, Schistosomulae and Adult Worms

SUMMARY Protective efficacy of the extracts of cercariae, schlst080mulae and aduH worms of S. mekongl was studied in mice receiving immunizations with these extracts emulsified with Freund's complete adjuvant Initially and incomplete adjuvant subsequently, and compared with mice receiving physiological saline with or without adjuvants as controls. After challenge with cercariae, the animals were sacrificed and the larvae or aduH worms harvested by lung recovery and perfusion :techniques on day 5 and weeks 6-8, respectively. Worm reduction rates were 8Ignlllcantly higher In mice receiving extracts of schlstosomula (59%) and adult worms (51 %) than In those receiving the cercarial extracts (31 %). Similar findings were obtained with the perfuSion technique showing worm reduction rates of 57%, 53% and 30% In mice receiving extracts of schistosomulae, adult worms and cercariae, respectively. ELISA antibody tltera were correspondingly Increased In mice receiving extracts of schlst080mulae and adult worms, but not In those receiving cercariae. This apparent association may be Inadequate to suggest that the increase In ELISA titer be used as an Indicator for reGlstance In mekongl schistosomiasis.