THE IMPACT OF THREE HERBICIDES ON BIOLOGICAL AND HISTOLOGICAL ASPECTS OF BIOMPHALARIA ALEXANDRIA, INTERMEDIATE HOST OF SCHISTOSOMA MANSONI

摘要

Schistosomiasis remains a public health problem in the developing world. Biomphalaria alexandrina is the intermediate host of Schistosoma mansoni, with a widespread distribution in Egypt. In Egypt molluscicides have been important, but otherwise molluscicides have been of minor significance. They may, however, become important now that WHO talks about eradicating schistosomiasis in some countries and that WHO has finally accepted that snail control is important.The present study investigated the different effects of three commercial herbicidical compounds, Butralin (as Amex 48% EC), glyphosate isopropylammonium (Herphosate 48% SL) and Pendimethalin (Stomp 50% EC) on S. alexandrina. All three compounds were found to have a molluscicidal effect, with Pendimethalin the most toxic over the examined range of concentrations. In addition, at sublethal concentrations, these compounds reduced growth rates and reproductive output (numbers of eggs laid) in exposed B. alexandrina, and it reduced viability of those eggs. Interpretion of assay data was supported by histological changes in the digestive and hermaphrodite glands of snails exposed at a range of concentrations. Moreover, the three compounds were also shown to rapidly (with three hours exposure) induce a toxic effect in miracidiae and cercariae of Schistosoma mansoni. It can be concluded that the three herbicidical compounds have molluscicidal and antihelminth properties.