In vitro cultivation of the sporogonic stages of Plasmodium: a review.

Complete and continuous in vitro development of the sporogonic stages of the malarial parasite has not yet been accomplished, although success with erythrocytic stages (falciparum malaria) and exoerythrocytic stages (avian malaria) has been achieved. This lag in progress appears to be due to several inherent differences between sporogony and these other sequences of development. The Trager-Jensen system for in vitro development of erythrocytic stages of Plasmodium falciparum results in the formation of gametocytes, although these gametocytes have not yet been shown to be functionally mature. An improvement in culture conditions, leading to the formation of infective gametocytes, would be an important advance. Culture systems for the transformation of gametocytes to ookinetes have been described, but whether this can be easily accomplished for falciparum malaria remains to be determined. The subsequent stages of sporogony, leading from oocyst differentiation to the formation of mature, infective sporozoites, have been successfully grown in short-term in vitro cultures. The entire developmental sequence, however, has been obtained only by overlapping successive stages in different cultures. This has established that all phases of sporogony are inherently capable of being supported in vitro. Further improvements may come through a better understanding of appropriate culture conditions.