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Susceptibility of Biomphalaria tenagophila hybrid descendants to two strains of Schistosoma mansoni

J.F. Scherrer; L.A Fallieri; J.R. de Freitas; M.C. Pagliaminuta; A.N. Faria

Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas icrais. Caixa Postal 2486. 30161 Belo Horizonte. MG. Brasil

ABSTRACT

There is little information in the literature about the genetics of snail susceptibility to Schistosoma mansoni, especially in relation to Biomphalaria tenagophila. Freitas et al. (Rev. Inst. Med. Trop. 27: 6-12, 1985), studying the susceptibility of B. tenagophila hybrids to the LE strain of S. mansoni (from Belo Horizonte, MG), noted that the maternal variety factor seemed to affect the results. To clarify this phenomenon, the present study was undertaken with the following objectives: a) to determine differences during the juvenile and adult phases between the albino variety of B. tenagophila from Joinville, SC, and the pigmented variety from Taim, RS, in terms of susceptibility to the LE and SJ strains of S. mansoni (from São José dos Campos, SP); and b) to determine the susceptibility of juvenile and adult F₁ hybrids resulting from crosses between the varieties Joinville and Taim to the LEand SJ strains of S. mansoni. Snails were mass-exposed to about 10, 25 and 50 miracidia per snail. When exposed to about 10 miracidia, juvenile and adult Taim snails were not susceptible to the LE and S.! strains. Juvenile and adult snails of the Joinville variety showed little (7.1% juvenile) or no susceptibility (adult) to the LE strain; however 86.1% of the juvenile snails and 74.0% of the adults were susceptible to the Si strain. Two different F₁s were considered: one resulting from crossing female Joinville snails with male Taim snails (Joinville female x Taim male) and the inverse (Taim female x Joinvile male). Juvenile and adult snails from both crosses were all refractory to infection by the LE strain as well as by the SJ strain. Another group of snails, 500 juvenile and 278 adult F₁ hybrids of the two crosses, were exposed to 25 or 50 SJ miracidia per snail, and all presented the same negative susceptibility results.

Keywords: Biomphalaria tenagophila; Hybrid; Schistosoma mansoni.

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