Studies on Anthelmintics of Common Liver Fluke

II. Anthelmintic Effect of Bithionol on Bovine Liver Fluke

Abstract

A series of compounds related to halogenated diphenyl sulfide and diphenyl methane were subjected to screening tests on the anthelmintic effect on liver flukes. As a result, it was made clear that bithionol and its close derivatives and hexachlorophene (G 11) functioned to remove liver flukes. This discovery was reported in the preceding paper. After that, the anthelmintic and side effects on sheep naturally infected with the parasite were compared between bithionol and G11. The results obtained indicate that G11 was more effective than bithionol, which could be used, however, with safety free from any side effect. They were already reported to the Japanese Society of Parasitology in October, 1959.
This paper deals with the optimal anthelmintic dose of bithionol against bovine, liver fluke and the side effect of this chemical.
1. Five cows were given a dose of 20mg/kg of bithionol mixed with feed, two cows a dose of 30mg/kg, two cows a dose of 35mg/kg, two cows a dose of 40mg/kg, one cow a dose of 50mg/kg, and one cow a dose of 55mg/kg. These cows had been infected with liver flukes. The results obtained from autopsy performed within 10 days after medication were as follows. No expected effect was shown by the dosage of 20mg/kg, which killed about half the number of liver flukes parasitizing. Of the two cows given 30mg/kg each, one still harbored flukes after medication, but the other revealed a complete removal of the worms. Adult liver flukos were expelled thoroughly from all the animals given a dose of 35mg/kg or more. From the parenchyma of the liver of the cow given a dose of 55mg/kg were detected a large number of young worms, one-third of which was clearly dead.
2. When about 150 cows were administered with two doses of 15mg/kg, or a single dose of 20, 30, or 35mg/kg by the same method in field trials of bithionol, the results of egg tests indicate that the medication of these doses was effective to remove parasitic eggs from 43.3, 42.9, 66.0, and 88.0 per cent, respectively, of the cows treated.
3. From the rate at which the results of liver fluke egg tests turned negative in the field trials, and the judgment on the anthelmintic effect at autopsy, a dose of 30 to 35mg/kg seemed to be the optimal one. Diarrhea occurred, however, in a cow given a dose of 35mg/kg. Therefore, the following doses were tentatively used, taking these results into consideration. Namely, a cow weighing 600kg was administered with 18g of the drug, one weighing 500kg with 16g, one weighing 400kg with 14g, and one weighing 300kg with 12g in the second field trials. As a result, parasite eggs disappeared from 77 per cent of the cows under medication. No conspicuous side-effects were observed in any one of them.