Schistosoma mansoni: analysis of an unusual infection phenotype in the intermediate host snail Biomphalaria glabrata.
Snails from a B. glabrata stock, selected for nonsusceptibility to the NMRI strain of S. mansoni, exhibited unusual schistosome infections, with multiple sporocysts prominent in the head-foot (foot-sporocysts). When F1 progeny from numerous crosses between well-defined susceptible (S) and resistant (R) parental snails were exposed, 60% of the infected snails also exhibited this unusual phenotype. F1 progeny from S x S snail crosses developed normal infections. Foot-sporocysts usually developed much later than secondary sporocysts of normal infections and before 12 weeks postexposure the tissue reaction surrounding foot-sporocysts was less intense than reactions to sporocysts in other tissues of the body. Cercariae were seen emerging directly from foot-sporocysts. Infection of S x R hybrid progeny by three other strains of S. mansoni also resulted in the production of foot-sporocysts. Development of the foot-sporocyst infection phenotype in progeny from many snail crosses suggests that this phenotype is more common than previously recognized. Over 50% of the F1 progeny from S x R parental crosses developed patent infections, a fact relevant to the possible biological control of schistosomiasis by the introduction of refractory snails into endemic areas.
Lewis
F A
FA
Biomedical Research Institute, Rockville, Maryland 20852.
Richards
C S
CS
Knight
M
M
Cooper
L A
LA
Clark
B
B
D000818:Animals; D001700:Biomphalaria / Q000469:parasitology*; D004199:Disease Vectors; D005260:Female; D006790:Host-Parasite Interactions; D008297:Male; D010641:Phenotype; D012550:Schistosoma mansoni / Q000254:growth & development* / Q000276:immunology