Chemotherapeutic and other studies on the pre-erythrocytic forms of simian malaria ( Plasmodium cynomolgi)

Abstract

1. (1) A study was made of the chemotherapeutic reactions of the pre-erythrocytic forms of Plasmodium cynomolgi. 2. (2) Quinine and mepacrine did not destroy these forms; neither did chloroquin, although it possibly diminished the number of pre-erythrocytic forms developing, and it caused vacuolation in them. 3. (3) Proguanil given daily during the prepatent period suppressed the pre-erythrocytic forms but did not prevent the development of a latent infection; if given towards the end of the prepatent period it caused vacuolation of the parasites. Sulphadiazine, given throughout the prepatent period, incompletely suppressed the parasites. 4. (4) Pamaquin given daily during the prepatent period completely prevented the infection. 5. (5) Sporozoites were injected intraperitoneally into two immune monkeys and the pre-erythrocytic forms developed apparently normally; but the resultant parasitaemia of the blood was very small and brief. This confirms the view that in malaria the immune mechanisms are directed against the forms in the blood and not against those in the tissues. 6. (6) Prolonged search for pre-erythrocytic parasites less than 4 days old was unsuccessful. 7. (7) Sporozoites of Plasmodium vivax were injected into the liver of a rhesus monkeys but not infection could be detected.