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Revista do Instituto de Medicina Tropical de São Paulo

On-line version ISSN 1678-9946


SOUZA, Cecília Pereira de; JANNOTTI-PASSOS, Liana K.; FERREIRA, Sueleny Silva  and  VIEIRA, Iaci Belo de Figueiredo. Schistosoma mansoni: the sex ratios of worms in animals infected with cercariae from three species of Biomphalaria. Rev. Inst. Med. trop. S. Paulo [online]. 1996, vol.38, n.2, pp.141-145. ISSN 1678-9946.

The ratios of male to female worms of Schistosoma mansoni were determined in mice infected with cercariae from LE, SJ and AL strains shed by mollusc hosts of the parasite in Brazil. The sex ratios of worms in the animals were similar with cercariae from Biomphialaria glabrata and B. tenagophila varying from 1.1:1 to 1.6:1 with LE and AL strains and 1:1.1 with SJ. In the animals infected with cercariae from B. straminea the ratio of male to female worms was similar to those obtained using cercariae shed from the other two species of molluscs, 1.5:1 with LE strain. Inoculations by AL and SJ cercariae resulted in sex ratios of 3.1:1 and 6:1 respectively. The normal sex ratios of worms established in Brazil in animals inoculated with cercariae from B. glabrata and B. tenagophila is from 1:1 to 2:1. The higher number of male worms that developed from cercariae of the AL and SJ strains obtained from B. straminea indicate a lower compatibility of the snail concerning these strains of S. mansoni.

Keywords : Schistosoma mansoni; Biomplialaria; Cercariae; Worms; Ratio male female.

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