Transformation of cercariae to schistosomula: a quantitative comparison of transformation techniques and of infectivity by different injection routes of the organisms produced.

Six transformation techniques ((1) incubation of cercariae in isotonic medium; (ii) penetration of isolated skin; (iii) stimulation with crude egg lecithin; (iv) mechanical disruption by passage through a syringe and 21 gauge needle; (v) by whorling of cercariae with a vortex mixer; (vi) syringe transformation followed by incubation) were evaluated. The organism produced were assessed for infectivity for mice by 6 different routes of infection (percutaneous, intradermal, subcutaneous, intra-peritoneal, intravenous and intra-muscular). At perfusion the largest numbers of adult worms were recovered from mice injected intramuscularly with organisms produced by the syringe technique and control mice given cercariae percutaneously. The peak for migration of schistosomula (following syringe transformation and intramuscular injection) through the lungs and the appearance of adult worms in the mesenteries was shown to be similar to cercarie administered percutaneously.