Transmission-blocking Effects of Primaquine and Methylene Blue Suggest Plasmodium falciparum Gametocyte Sterilization Rather Than Effects on Sex Ratio

Gametocyte density and sex ratio can predict the proportion of mosquitoes that will become infected after feeding on blood of patients receiving nongametocytocidal drugs. Because primaquine and methylene blue sterilize gametocytes before affecting their density and sex ratio, mosquito feeding experiments are required to demonstrate their early transmission-blocking effects.