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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 90, No. 2, 1995, pp. 195-204
Bioline Code: oc95040
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 90, No. 2, 1995, pp. 195-204

 en The Snail Hosts of Schistosomiasis: Some Evolutionary and Ecological Perspectives in Relation to Control
JD Thomas

Abstract

Despite opportunities for radiation provided by spatio-
temporal isolation, the basic morphological plan of pulmonate
snails has remained conservative. In consequence of the
resulting dearth of morphological characters and their
plasticity, there is a case for using biochemical characters
such as exogenous chemicals released by the snails (e.g. amino
acids) and their chemoreception niche as taxonomic aids to
classify snails of medical importance.  As these same
chemicals are used by snails to distinguish conspecifics they
could also be used as 'environmental antibodies  in controlled
release formulations (CRF's) designed to remove target snails
in a specific, cost-effective and ecologically acceptable
manner.

The snails, surface-living bacteria, algae and macrophytic plants are considered as co-evolved, interactive modular systems with strong mutualistic elements. Recently, anthropogenic perturbations such as deforestation, and damming of flowing waters, have benefited these modules whereas others such as river canalization, acid deposition, accumulation of pesticide residues and eutrophication have harmed them. Research is needed to elucidate the factors which limit the growth of snails in primitive habitats, uninfluenced by man, as well as in those subject to harmful anthropogenic factors. The understanding thus gained could be applied to develop cost-effective primary health care strategies to reduce or prevent transmission of schistosomiasis and other water related diseases.

Keywords
pulmonate-molluscs - evolution - taxonomy - controlled release formulations - control

 
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