In the human body the parasite injected into the bloodstream by the mosquito undergoes the transformation from the asexual plasmodium into the sexual gametocytes which the mosquito is going to pick-up during its blood meal. The killing effect of artemisinin on gametocytes is known since twenty years and was first mentioned in in vitro trials at the John Hopkins University. These results were confirmed in 1993 by research teams in China and India and mentioned in the document WHO/MAL/98.1086. The Malaria Journal published a review article (1)in 2008 describing similar studies involving a few thousand people in several countries.
Taking regularly a cup of Artemisia annua tea could strongly reduce not only the plasmodium but also the gametocyte load in the blood. We have received many anecdotic reports of this kind from African partners, but the effect deserves a well designed series of clinical trials in different human and geographical environment. Several are planned in vitro and in vivo in cooperation with BELHERB (Association belgo-luxembourgeise pour la promotion des herbes médicinales). Children appear to constitute the majority of carriers of gametocytes as a study in Kenya showed (2). It appears that the anopheles mosquito is preferably attracted by children and especially by those who are carriers of gametocytes. The efforts should thus concentrate on school children.
Another study in Kenya (KEMRI-ICIPE-KIT) has shown that the prevalence of submicroscopic gametocytaemia in children is in fact much higher than expected and that asymptomatic individuals are major reservoirs of infection because parasites from asymptomatic carriers are more infectious to mosquitoes than are parasites from symptomatic individuals. Most antimalarial drugs like chloroquine, amodiaquine, don’t have a known gametocytocidal effect. Pyrimethamine-sulfadoxine (SP) even increases the gametocyte density. Artesunate-lumefantrine and artesunate-amodiaquine increase gametocyte infectivity to anopheles mosquitoes (3)and may lead to higher endemicity. Only primaquine has a moderate gametocytocidal effect on mature gametocytes and needs thus to be taken some weeks after the 3 day ACT cure. Artemisia annua tea taken over 7 days presents the advantage of this longer duration of treatment because gametocytes generally only develop after the 5th day of the infection and artemisinin is very effective against young gametocytes. The chemical derivates of artemisinin (artesunate, artemether) in combination with other antimalarials (ACT) could be less effective because the treatment is limited to 3 days.
Furthermore flavonoids, polysaccharides and essential oils which are present in the tea like 1.8 cineol (4) and limonene (5) are known as antimalarials, they arrest parasite development at an early stage and inhibit thus the formation of mature gametocytes by acting on the apicoplast. Their presence may explain why actually Artemisia annua treats malaria in doses of artemisinin far less than WHO doses and even has a prophylactic effect against malaria by strengthening the immune system (6) The dream of malaria eradication with artemisia tea could become true
Abstract of the data presented at the Conference on “Health and Education in Africa – Fighting malaria and dysentery” at the European Parliament in Brussels on June 16th 2011. The full text in French is available on request, firstname.lastname@example.org
(1) LC Okell et al, Malaria Journal, 2008, 7(125) (2) LC Gouagna et al., East Afr Med Journ., 2003, 80 (12) 627-634 (3) B Fofana, MIMconf Kenya Nov. 2009 (4) Vanessa Su et al., Flavour Fragr. J. 2008; 23: 315–318 (5) IC Moura et al.,Antimicrobial Agents and Chemotherapy, Sept 2001, 45 (9) 2553-58, (6) PE Ogwang et al., Trop J Pharmaceutical Research, 2012, 13(3) 445-453