Plasmodium vivax: gametocyte infectivity of naturally infected Thai adults.

Up to 200 laboratory reared Anopheles dirus mosquitoes were fed on each of 496 symptomatic Thai men who had patent, naturally acquired Plasmodium vivax gametocytaemia. Mean gametocyte densities were 455/mm3 (range: 0-3281), geometric mean oocyst number was 9 (0-142), mean frequency of infection was 43% (0-100%), and mean sporozoite number in salivary glands was 9525 (0-285,000). There was little relation between gametocyte density and either oocyst number or frequency of mosquito infection. There were, however, statistically strong positive correlations between oocyst numbers and frequency of infection, and between number of oocysts and number of salivary gland sporozoites. The data suggest that each oocyst contributed about 850 sporozoites to a gland infection.