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The authors consider evident similarities of toxic effects in the treatment of human african trypanosomiasis with Arsobal, and those in the treatment of syphilis with arsenobenzole derivatives. Considering that a majority of authors recommended adrenaline as a preventive and curative measure in the course of arsenobenzole encephalopathy, the authors have experimented this same medication in the prevention and treatment of toxic side effects caused by Arsobal therapy of H.A.T. In the course of treating 776 sleeping sickness patients with Arsobal in conjunction with adrenaline, an incidence of 1,54 p. 100 (13 patients) of hemorrhagic encephalopathy was registered. On the other hand, the association of adrenaline (or others therapeutic drugs with alpha- and bêta-activity) with others therapeutic drugs currently used, resulted in a 92 p. 100 recovery of the patients with hemorrhagic th encephalopathy. The authors have accordingly attempted to postulate some possible hypothesis on the mechanism of action of the above therapeutic association.

The best hope for the control of transmission of Onchocerca volvulus over much of Africa lies in combining larvicidal measures directed against the Simulium vectors with chemotherapeutic measures designed to reduce the reservoir of transmissible microfilariae in man.There are few drugs effective against O. volvulus. Diethylcarbamazine kills the microfilariae but has virtually no effect on the adult worms. Suramin kills adult worms and many, but not all, of the microfilariae. Mel W kills adult worms but has little or no action on microfilariae. All these drugs suffer at present from disadvantages of toxicity, which tend to limit their use on a mass scale in the field. Nevertheless, before they, or indeed any new drugs with similar actions on the parasites, can be used intelligently for the control of onchocerciasis transmission, it is necessary to have accurate quantitative information on the effect that each of them has on the microfilarial population available for intake by Simulium, as well as on their actions on the developmental potential of those microfilariae ingested by the flies.The present paper describes the effects of treatment with various courses of diethylcarbamazine, suramin or Mel W on the numbers of microfilariae ingested by groups of S. damnosum and on the numbers of infective larvae developing therefrom.

Previous work on monkeys and on human volunteers led to the development of a schedule of diethylcarbamazine dosage suitable for the chemoprophylaxis of loiasis. In several parts of Africa where this chemoprophylaxis is practised against Loa loa, infections with Onchocerca volvulus are also common. Attempts were therefore made to determine whether diethylcarbamazine has any prophylactic action against the latter parasite by making use of chimpanzees exposed to experimental infections, and also by using biopsy techniques to study the fate of infective larvae inoculated into volunteers.Both experimental methods proved more difficult to apply in O. volvulus infections than had been the case with L. loa, but evidence was obtained that diethylcarbamazine is not an effective chemoprophylactic for O. volvulus.Further experiments were then carried out with suramin and with melarsonyl potassium (Mel W). Although both gave some evidence of partial prophylactic activity, their use for this purpose is at present neither practical nor safe.