Febrile temperatures influence the transmission competence of mature Plasmodium falciparum gametocytes

Malaria transmission depends on the survival and mosquito infectivity of mature Plasmodium falciparum gametocytes. Despite malaria febrile episodes reaching 39- 41.5°C in infected humans, the impact of febrile temperatures of varying durations on gametocyte viability and transmissibility remains undefined. Here we quantify the effects of exposing mature stage V gametocytes in vitro to febrile temperatures (39°C, 40°C, and 41.5°C) for varying durations (3-12 hours). To assess gametocyte morphology, functionality, and mosquito infectivity, we used light microscopy of Giemsa-stained thin blood smears, exflagellation assays, and standard membrane feeding assays (SMFAs) respectively.

Following exposure to 39°C, gametocytes retained normal morphology, exflagellation capacity, and mosquito infectivity across all exposure durations. At40°C, gametocytes remained morphologically intact and capable of exflagellation but exhibited a time-dependent reduction in mosquito infection, both in prevalence and oocyst intensity, following prolonged exposure. In contrast, exposure of mature gametocytes to 41.5°C, even for the minimum duration tested of 3 hours, resulted in complete loss of normal morphology, exflagellation capacity and ability to infect mosquitoes.

These findings reveal that mosquito infectivity of mature gametocytes is affected both by the magnitude of the febrile temperature and the duration of exposure. This provides insights into how host fever dynamics may influence parasite transmission.