Development of a Method for the In Vitro Production of Plasmodium vivax Ookinetes

We developed a method for the in vitro production of mature Plasmodium vivax ookinetes. Gametocytemic blood was collected from 98 P. vivax-infected patients reporting to malaria clinics in Maesod and Maekasa Districts, Tak Province, Thailand. Briefly, gametogenesis was induced using xanthurenic acid and parasites were separated by density gradient centrifugation and then cultured in RPMI-1640, pH 7.8–8.2. At the same time that blood was collected, 200 Anopheles dirus mosquitoes were allowed to feed on each patient. Mosquito midguts were removed 2–36 hr postfeeding, and gut contents were smeared onto glass slides, as were cultured samples from varying time points. Slides were stained with Giemsa, and the in vitro and mosquito development of ookinetes compared. Mature ookinetes were produced in 48.0% (47/98) of in vitro cultures, with a total yield ranging from 10 to 248,500 (x = 15,523, median = 600) ookinetes produced per 5 ml blood. The temporal development and the morphology of the P. vivax ookinetes p...