Febrile temperatures influence the transmission competence of mature Plasmodium falciparum gametocytes

The transmission of malaria is contingent upon the survival and infectivity of mature Plasmodium falciparum gametocytes within mosquitoes. Previous research has shown that fever episodes in infected individuals can reach temperatures between 39°C and 41.5°C, yet the effects of these febrile temperatures on gametocyte viability and transmission potential have not been extensively studied.

This investigation aimed to measure the influence of exposing mature stage V gametocytes in a controlled environment to febrile temperatures of 39°C, 40°C, and 41.5°C, for durations ranging from 3 to 12 hours. The researchers utilized light microscopy of Giemsa-stained thin blood smears, exflagellation assays, and standard membrane feeding assays (SMFAs) to evaluate gametocyte morphology, functionality, and mosquito infectivity.

Upon exposure to 39°C, the gametocytes maintained their normal morphology, maintained their ability to undergo exflagellation, and retained their capacity for mosquito infection across all exposure periods. However, when exposed to 40°C, the gametocytes remained morphologically intact and capable of exflagellation but demonstrated a decrease in infection prevalence and oocyst intensity with extended exposure periods.

Conversely, when exposed to 41.5°C, even for the short duration of 3 hours, the mature gametocytes showed complete loss of normal morphology, exflagellation capacity, and their ability to infect mosquitoes. These results indicate that the mosquito infectivity of mature gametocytes is influenced by both the intensity of the febrile temperature and the length of exposure.

This study provides valuable insight into how variations in host fever dynamics may impact the transmission of the malaria parasite.