Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Tropical Diseases, P. O. Box 717, Columbia, South Carolina
In 20 cases of Chesson strain Plasmodium vivax malaria treated with chloroquine, infectivity to mosquitoes ceased as a rule after the first post-treatment day; in one case only, after the second. In three cases treated with at least 100 mg. of chlorguanide, infectivity to mosquitoes was terminated within the first 24 hours. In one instance a single 50 mg. dose of chlorguanide interrupted infectivity 24 hours, but infectivity then returned and persisted as long as sufficient parasites were present. In a single case treated with 25 mg. of pyrimethamine, infectivity was eliminated within four hours. However, a case resistant to this drug readily infected mosquitoes during and after multiple daily doses. Intramuscular sodium bismuth thioglycollate (0.1 gm.) temporarily eliminated gametocytes and infectivity to mosquitoes within 24 to 48 hours, but both reappeared after one or two days.