Experimental infection of white mice (Swiss inbred) with LE strain Scistosoma mansoni cercariae submitted to the action of magnesium thermophosphate (Tfm), usually used in tropical latosoils, was performed. This product is able to block ovogenesis of planorbid molluscs. In these experimental conditions, rodents were infected. But, the number of eggs released by the control group (five mice) was markedly greater than that of the Tfm group, although a short number of worms were recovered by perfusion. From the Tfm group, 163 adult worms (98,2%) were recovered and only 3 females (1,8%). Of the control group, perfusion recovered 62 adult worms (22 male worms, 18 female and 11 couples). Each mice was exposed to 150 cercariae.
