1. Screening tests were carried out on the anthelmintic action of four diphenylmethanes and three diphenyl sulfides upon rabbits infected experimentally more than 60 days before. Two rabbits received a dose of 100mg of each chemical per kg of body weight by the oral route. They were killed on the 6th or 7th day after medication for the judgment of the anthelmintic effect. As a result, dichlorophene, G. 5, 4, 4'-tetrachlorodiphenylmethane, and 2, 2'-dihydroxy-5, 5'-dichlorodiphenyl sulfide revealed no effect, while bithionol, bithionol acetate, and hexachlorophene ware found effective. Of these three, hexachlorophene was very toxic forrabbits and bithionol acetate seemed to be a little less effective than bithionol. Bithionol was the best of the three, removing the flukes completely without showing any side reaction.
2. Bithionol, which displayed the most effective action and no side reaction in screening tests on rabbits, was administered perorally to one naturally infected sheep in a dose of 300mg/kg and two naturally infected sheep each in a dose of 50, 75, 100, and 200mg/kg, respectively. The effects were judged in these sheep in the same manner as in the rabbits. As a result, the medication of the doses of 75, 200, and 300mg/kg removed the flukes thoroughly. A small number of dead flukes were observed after the dosage of 100mg/kg in one sheep. Also a small number of living flukes were collected from the sheep given 50mg/kg, although a considerably large number of flukes seemed to have been removed after administration. No side reaction was observed at the dosage of 75 and 100mg/kg. Moreover, Dicrocoelium worms harbored by two sheep receiving a dose of 100mg/kg were found, at autopsy, to have been almost all removed, leaving only trace of habitation.
3. The results of anthelmintic experiments indicate that bithionol was not potent enough to kill young liver flukes in rabbits at the dose of 100 or 200mg/kg and those in sheep at the dose of 75 mg/kg. It is assumed that this drug has no effect on young worms in the tissue.
As the ultimate objective of these experiments is to remove liver flukes from cattle, field trials are now going on with a large number of bovine liver flukes.
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