1. Chemotherapy for oesophagostomiasis must be based on the administration of the remedy into the abomasum. At first a 1 per cent. copper sulphate solution was used for stimulation of the oesophageal reflex, then higher concentrations until finally satisfactory results were obtained with 2.5 c.c. of a 10 per cent. solution.
2. Preliminary tests were made with 15 different chemicals which had either previously given indications that they may be effective, or appeared, according to their chemical and physical properties, to be suitable. Of these copper arsenate and copper tartrate gave rather outstanding results.
3. Both these drugs were found to be dangerous in doses which would be large enough to effect a cure. An overdose of copper arsenate leads to arsenical poisoning while an overdose of copper tartrate leads to copper poisoning.
4. A mixture of the two drugs produced variable results which were found to be connected with the variable amount of acid in the abomasum. Since the drugs are relatively soluble in acid and alkaline media, high stomach acidity would cause solution and absorption of the drugs with consequent poisoning of the sheep and little or no effect against the parasites. Calcium hydroxide was found to be a suitable corrective and was incorporated in the mixture. Effective doses of this mixture were found to possess a suitable degree of safety even if treatment is repeated at relatively short intervals.
5. Taking into account all ages and conditions of sheep, the efficacy of one treatment, i.e. a dose on each of two successive days, is expected to reach at least 75 per cent. If only young sheep under 2 years of age are treated the efficacy will be considerably higher.
6. It has incidentally been observed that the mixture has a fair degree of efficacy against Haemonchus contortus and Moniezia expansa.
7. Measures for treatment and prevention of oesophagostomiasis by means of a suitable remedy under South African conditions are outlined.