Infectivity of Schistosoma Mansoni for Puerto Rican Mollusks, Including a new Potential Intermediate Host

Charles S. Richards Puerto Rico Field Station, Technical Development Laboratories, Technology Branch, Communicable Disease Center, Public Health Service, U. S. Department of Health, Education, and Welfare, San Juan, , Puerto Rico

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Laboratory experiments involved exposure of 1,521 Puerto Rican fresh-water mollusks of 22 species to miracidia of Schistosoma mansoni. Frequency of observed penetration in descending order was as follows: Tropicorbis obstructus, Australorbis glabratus, Tropicorbis riisei, Tropicorbis albicans, Aplexa marmorata, Pleisophysa hubendicki, and Drepanotrema simmonsi. Successful infection with shedding of cercariae was observed in A. glabratus, T. riisei, and T. albicans. Eighteen of 642 (3%) T. riisei infected involved 3 of 64 collections, and four of 172 (2%) T. albicans infected involved 2 of 25 collections. This is believed to be the first report of infection of T. albicans with S. mansoni, adding a third known potential intermediate host snail species in Puerto Rico.

Results suggested that susceptibility in T. riisei and T. albicans has a genetic basis and that successful infection of these species by S. mansoni was influenced by the effect of prior penetration by miracidia of S. mansoni or other trematodes.

Author Notes

Present address: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda 14, Maryland.