The Gametocytocidal Activity of Whole-Plant Artemisia annua and Artemisia afra Tea-Based Therapies against Plasmodium falciparum in vitro.
Malaria is one of the deadliest parasitic diseases worldwide, causing 219 million infections and 435 thousand deaths per year. As such, this mosquito-borne illness is a major target for global eradication efforts. One critical arm of the eradication strategy is chemotherapy. For a therapeutic to advance the eradication agenda, it must cure the patient of infection and eliminate transmission stage parasites (called gametocytes) from the blood, thereby breaking the cycle of transmission. Currently, first-line treatments against malaria infection consist of an artemisinin derivative in combination with another antimalarial drug from a different drug class. Although artemisinin and its derivatives are highly efficacious at curing malaria, these drugs are ineffective at preventing disease transmission. However, recent in vivo studies have suggested that whole plant Artemisia annua (the botanical source of artemisinin) delivered as tea can cure patients of infection and eliminate transmission stage parasites from the bloodstream. To validate these in vivo results in vitro, experiments were performed to measure the killing efficacy of A. annua and A. afra tea infusions against three different stages of the parasite life cycle— one stage of the asexual cycle, immature gametocytes, and mature gametocytes. Killing effects were observed using light microscopy and gametocyte gene-specific RT-qPCR analyses. Results suggested that A. annua tea was nearly as effective as artemisinin at killing all three tested stages of the parasite. A. afra tea, which contains low levels of artemisinin, showed comparable killing efficacy against late stage gametocytes, but not against the other two tested stages. These results supported the notion that A. annua tea is an effective antimalarial and also provides evidence that both A. annua and A. afra teas may be a viable therapeutic option for eliminating gametocytes during human infection.