IMMUNIZATION OF MICE WITH ULTRAVIOLET-ATTENUATED CERCARIAE OF SCHISTOSOMA-MANSONI TRANSIENTLY REDUCES THE FECUNDITY OF CHALLENGE WORMS

In the present study cohorts of ICR and BALB/c mice were immunized wit h u.v.-irradiated cercariae of S. mansoni and challenged 5 weeks later , in parallel with unimmunized control mice, with approximately 100 ce rcariae, Total worm burdens at 5, 6, 7 and 8 weeks after challenge wer e significantly reduced by 27-65% in immunized mice, The total number of eggs and the number of eggs/female worm trapped in Liver and small intestine were reduced significantly at 6 and 7 weeks post challenge i n immunized, as compared to unimmunized mice. Decrease in tissue egg l oad could be achieved in BALB/c mice passively transferred with spleen cells from u.v.-attenuated cercaria-immunized mice. The proportion of female worms laying eggs ill vitro was diminished only in worms recov ered from highly resistant mice, The reduction in worm oviposition in immunized mice was no longer apparent at 8 weeks, The data taken toget her indicate that highly effective immunization of outbred and inbred mice with attenuated cercariae leads to significant, but transient, im pairment in challenge worm egg production. (C) 1997 Australian Society for Parasitology.