Development of Resistance to Molluscicides in Oncomelania Nosophora

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  • 406th Medical General Laboratory, APO 343, San Francisco, California


Immersion tests were conducted with O. nosophora collected from areas treated for several years with sodium pentachlorophenate and dinitro-o-cyclohexylphenol, and from neighboring control areas, to determine if resistance has developed to these molluscicides in the treated snail populations. No resistance to Na-PCP was demonstrated in snails from areas which had been treated for 7 years, and 4 years, respectively. However, there was a marked degree of resistance to dinitro-o-cyclohexylphenol in snails from a locality which had been treated with DN-1 for 6 years.