Rescue of sporocysts of Schistosoma mansoni in nonsusceptible Biomphalariaby head-foot transplantation into susceptible snails

To measure the longevity of sporocysts of Schistosoma mansoni in nonsuscept ible snails (13-16-R1 and Salvador strains of Biomphalaria glabrata, and Bi omphalaria obstructa), the head-foot (HF) of miracidia-exposed snails was t ransplanted into the hemocoel of a susceptible NIH albino recipient at 1-36 days postexposure (DPE). Recipient snails which were not exposed to miraci dia then were monitored for infection transferred by the implant. and infec tion prevalences in recipients of HF transplants from nonsusceptible donors were compared to those in snails implanted with an HF from NIH albino dono rs. Transplants from NIH albino snails between 1 to 15 DPE infected 98% of recipients. Similarly, at 1 DPE, 69-85% of transplants from nonsusceptible snails contained viable sporocysts, as shown by resulting patent infections in the recipients. Recipient infection prevalence, and presumably numbers of transplants containing viable sporocysts, declined as a function of DPE, and by 5-9 DPE this decrease was significant for all 3 types of nonsuscept ible donors. However, viable sporocysts still occurred in B. obstructa and 13-16-R1 B. glabrata as late as 19 and 20 DPE, respectively, and in Salvado r B. glabrata as late as 33 DPE. Thus, sporocysts persist in nonsusceptible snails considerably longer than suggested by results of previous histologi cal studies.