It is generally or it was believed that quinine is prophylactic. But several papers have questionned this believe and a large scale clinical trial from India in 1918 demonstrated that it is not the case and that large quantities of quinine have been swallowed by a large number of people without providing protection against the infection nor significantly reducing transmission
G Waugh Scott. Quinine prophylaxis in malaria. Brit Med Journal, 1918, May 11th.
NJ Serlin, JR Lisa. A concentration technic for gametocytes of estivo-atumnal malaria. Am J Clin Pathology 1942, 12, p8
However concerning artesunate a recent paper from Mali is alarming. Artesunate did not clear mature gametocytes during treatment and did not prevent the appearance of new stage V gametocytes as assessed by light microscopy. Baseline gametocyte carriage was significantly higher 6 years after the deployment of artemisinin-based combination therapies in this setting What worries the authors of the 2016 study from Mali is not only that similar results had been found in a study in 2002-2004, but the fact that baseline gametocyte carriage was significantly higher 6 years later. If artemisinin derivatives really enhance recrudescence and gametocyte carriage, this is indeed alarming. It would mean that ACTs will not eradicate malaria but enhance it in the long run.
Abdoulaye A. Djimde, Amelia W. Maiga. Gametocyte clearance dynamics following oral artesunate treatment of uncomplicated falciparum malaria in Malian children. Parasite. 2016; 23: 3.
The same recrudescence with oral artemisinin monotherapy had already been observed in Vietnam in 2001.
P T Giao, T Q Binh, P A Kager, H P Long, N Van Thang, N Van Nam and P J de Vries. Artemisinin for treatment of uncomplicated falciparum malaria: is there a place for monotherapy? Am J Trop Med Hyg, 2001 65 690-695
Artesunate does not clear mature gametocytes during oral artesunate treatment and does not prevent the appearance of new gametocytes. This confirms to a large extent the randomized, double blind, large scale clinical trials run in Maniema-Congo end of last year. After 14 days up to day 28 gametocytes had completely disappeared in those treated with Artemisia annua and Artemisia afra herbal infusion, but it was still present on day 28 in 10% of those treated with ASAQ.
Munyangi J, Lutgen P, Cornet-Vernet L., Artemisia plants : a deadly weapon against tropical diseases. Int J Clin Res Trials 2016, : 109 .doi.org/10.15344/ijcrt/2016/109
It is in line with the findings of the Worcester Polytechnic Institute that dried whole-plant Artemisia annua slows evolution of malaria drug resistance and overcomes resistance to artemisinin.
Elfawal MA, Towler MJ, Reich NG, Weathers PJ, Rich SM. Dried whole-plant Artemisia annua slows evolution of malaria drug resistance and overcomes resistance to artemisinin. Proc Natl Acad Sci U S A. 2015 Jan 20;112(3):821-6. doi: 10.1073/pnas.1413127112.
A recent paper of a South African research team shows that among 8 medicinal plants Artemisia afra has the lowest IC50 for impairing the development of late stage gametocytes. A very important finding as not many plants have such a significant gametocytocidal effect
P. Moyo, M.E. Botha, . In vitro inhibition of Plasmodium falciparum early and late stage gametocyte viability by extracts from eight traditionally used South African plant species , Journal of Ethnopharmacology > 2016 . 185 235-242
The findings of a study in Burkina Faso suggest that although gametocytes are most commonly detected in children, the proportion of asexual parasites that is committed to develop into gametocytes may increase with age. These findings underscore the importance of adults for the human infectious reservoir for malaria.
André Lin Ouédraogo, Teun Bousema, Sake J de Vlas, Nadine Cuzin-Ouattara, Jan-Peter Verhave, and Robert Sauerwein. The plasticity of Plasmodium falciparum gametocytaemia in relation to age in Burkina Faso. Malaria Journal 20109:281 DOI: 10.1186/1475-2875-9-281
The conclusion of the authors was that artemisinin monotherapy may offer rapid recovery and fast parasite clearance, but recrudescence is frequent. For up to 20 percent of the cases on day 28, although gametocytes had completely disappeared on day 7. Extending the duration of the monotherapy from 5 to 7 days did not reduce recrudescence. A study from Kenya had also found that gametocyte carriage was much lower on day 14 than on day 28 and 42 for artemether lumefantrine, but not for dihydroartemisinin-piperaquine.
Sawa P, Shekalaghe SA, Drakeley CJ, Sutherland CJ, Mweresa CK, Bousema T. Malaria transmission after artemether-lumefantrine and dihydroartemisinin-piperaquine: a randomized trial. J Infect Dis. 2013 Jun 1;207(11):1637-45. doi: 10.1093/infdis/jit077.
To reduce or eradicate transmission, it is important to eliminate male and female gametocytes. Artemisinin and its derivatives play a dubious role in this field
Table 2 from : MJ Delves, A Ruecker. Male and female Plasmodium falciparum Mature gametocytes show different responses to antimalarial drugs. Antimicrob. Ag Chemother. July 2013 vol. 57 no. 7 3268-327
It is well known that artemisinin drugs are gametocytocidal for immature, but not mature gametocytes. A paper of the Swiss Tropical and Public Health Institute comes to the conclusion that in high perennial transmission settings case management with ACT may have little impact on overall infectiousness of the human population. They even found in their study, that the most direct indicator of human-to-mosquito transmission, namely oocyst prevalence was substantially higher after ACT introduction. A study from Burkina Faso found in a recheck 12 months after a clinical trial with ACTs that the number of symptomatic malaria episodes was even slightly higher in the ACT arm than in the control arm and that after several treatments the prevalence of gametocyte carriers was the same in both arms.
Bernadette J Huho, Gerard F Killeen, Heather M Ferguson, Adriana Tami, Christian Lengeler, Artemisinin-based combination therapy does not measurably reduce human infectiousness to vectors in a setting of intense malaria transmission. Malaria Journal 201211:118
Alfred B Tiono, Alphonse Ouédraogo, Bernhards Ogutu, A controlled, parallel, cluster-randomized trial of community-wide screening and treatment of asymptomatic carriers of Plasmodium falciparum in Burkina Faso. Malaria Journal 201312:79 DOI: 10.1186/1475-2875-12-79
Another study found that ACT did not significantly reduce the proportion of infectious children. Submicroscopic gametocytaemia is common after treatment and contributes considerably to mosquito infection. Because of the short half-life of artemisinin and because high doses induce dormancy in the asexual parasite. Asexual forms, mostly rings, remaining after completion of ACT treatment may develop into mature gametocytes 7-15 days later.
Johanna M. Roth, Patrick Sawa, Plasmodium falciparum gametocyte dynamics after pyronaridine–artesunate or artemether–lumefantrine treatment Malaria Journal 2018 17:223, 4
Chemotherapy could enhance the circulation of more virulent strains by keeping alive patients who would otherwise have died from virulent infections.
Sylvain Gandon, Margaret J. Mackinnon, Sean Nee & Andrew F. Read. Imperfect vaccines and the evolution of pathogen virulence. Nature 414, 751-756 (13 December 2001) | doi:10.1038/414751a
This has been seen in the case of RTS,S vaccines.
A Olutu, G Fegan, P Bejon. Seven-year efficacy of RTS,S/AS01 malaria vaccine amoung young African children. NEJM, 2016, 374, 2519-2529
New gametocyte detection techniques have shown that submicroscopical gametocyte carriage is common and contributes substanially to the human infectuous reservoir. Quantifying the gametocytes by microscopy and by nucleic acid sequence-based amplification assay (QT-NASBA) in children in Burkina Faso : by microscopy only 30.0% of the children were found to be carriers of gametocytes versus 91.6% by QT-NASBA. Several studies show that mosquitoes can become infected with gametocyte densities below the detection level of standard microscopy. Individuals with low gametocyte densities undetectable by microscopy may still be infectious to mosquitoes P. falciparum gametocyte carriers usually harbour less than 100 gametocyte µl−1 blood and there is evidence that 1–10 gametocytes µl−1 blood are infectious to mosquitoes
Schneider P, Bousema JT, Gouagna LC, Otieno S, van de Vegte-Bolmer M, Omar SA, Sauerwein RW: Submicroscopic Plasmodium falciparum gametocyte densities frequently result in mosquito infection. Am J Trop Med Hyg 2007, 76:470-474.
Ouedraogo AL, Bousema T, Luty AJ, Sauerwein R, Substantial contribution of submicroscopical Plasmodium falciparum gametocyte carriage to the infectious reservoir in an area of seasonal transmission. PLoS One 2009, 4:e8410
Muirhead-Thomson RC. Factors determining the true reservoir of infection of Plasmodium falciparum and Wuchereria bancrofti in a West African village. Trans R Soc Trop Med Hyg 1954, 48: 208–225.
D Bunna, T Harinsuta. S Pinichipongse, P Suntharasamai. A randomized open-label trial of artesunate- sulfadoxine-pyrimethamine with or without primaquine for elimination of sub-microscopic P. falciparum parasitaemia and gametocyte carriage in eastern Sudan. Science Report, 2007. Vol 2.
A study from Brazil concerning asymptomatic carriers in the Amazon region comes to similar conclusions. Although the asymptomatic group infected mosquitoes at a much lower rate, these patients remain infective longer than symptomatic patients. Also, the prevalence of asymptomatic infections is 4 to 5 times higher than symptomatic infections among natives. These results have implications for the malaria control program in Brazil, which focuses essentially on the treatment of symptomatic patients.
Alves FP, Gil LH, Marrelli MT, Ribolla PE, Camargo EP, Da Silva LH.Asymptomatic carriers of Plasmodium spp. as infection source for malaria vector mosquitoes in the Brazilian Amazon. J Med Entomol. 2005 Sep;42(5):777-9.
A recent study of the University of Kinshasa also shows a high gametocyte presence in asymptomatic carriers. A challende for the bodies involved in malaria control in DR Congo to take into account asymptomatic carriers in actions taken and consider asymptomatic malaria as a major hurdle for malaria elimination.
Dieudonné Makaba Mvumbi, Thierry Lengu Bobanga, Georges LeloMvumbi, High Prevalence of Plasmodium falciparum Infection in Asymptomatic Individuals from the Democratic Republic of the Congo. Malaria Research and Treatment Volume 2016, Article ID 5405802, 4 pages doi.org/10.1155/2016/5405802.
Gametocyte carriage even increases attractiveness of humans to mosquitoes.
Renaud Lacroix, Jacob C Koella. Malaria Infection Increases Attractiveness of Humans to Mosquitoes PLOS 2009 http://dx.doi.org/10.1371/journal.pbio.0030298
Adults contribute significantly to the infectious reservoir, particularly in areas of intense seasonal transmission.
Drakeley CJ, Akim NI, Sauerwein RW, Greenwood BM, Targett GA. 2000. Estimates of the infectious reservoir of Plasmodium falciparum malaria in the Gambia and in Tanzania. Trans R Soc Trop Med Hyg 94:472–6. 10.1016/S0035-9203(00)90056-7 [PubMed] [Cross Ref]
Drakeley CJ, Bousema JT, Akim NI, Teelen K, Roeffen W, Lensen AH. 2006. Transmission-reducing immunity is inversely related to age in Plasmodium falciparum gametocyte carriers. Parasite Immunol 28:185–90. 10.1111/j.1365-3024.2005.00818.x [PubMed] [Cross Ref]
Hopefully a recent study from the Worcester Technical Institute shows that Artemisia annua dried leaves are able to reverse the resistance induced by artemisinin and derivatives.
Mostafa A. Elfawal, Melissa J. Towler, Nicholas G. Reich, Pamela J. Weathers, and Stephen M. Richa,. Dried whole-plant Artemisia annua slows evolution of malaria drug resistance and overcomes resistance to artemisinin. Proc Natl Acad Sci U S A. 2015 Jan 20; 112(3): 821–826.
And this has become a larger field of study, leading even to the publication of a book
Mahendra Rai, Kateryna Kon, Fighting multidrug resistance with herbal extracts, essential oils and their components. Academic Press 2013.
Immunity to malaria is slow and short-lived despite the repeated parasite exposure in endemic areas. Malaria parasites have evolved refined machinery to evade the immune system based on a range of genetic changes that include allelic variation, biomolecular exposure of proteins, and intracellular replication. All of these features increase the probability of survival in both mosquitoes and the vertebrate host. In the human host, Plasmodium species employ various immune evasion strategies during different life cycle stages. Parasite persistence against the vertebrate immune response depends on the balance among virulence factors, pathology, metabolic cost of the host immune response, and the parasites ability to evade the immune response.
Artemisinin and its chemical derivatives, as well as amodiaquine and mefloquine are immunodepressive. As for ACTs they may give spectacular results in the short run, but be detrimental in the long run for malaria eradication. PCR at day 28 is a vain effort if it is not done in parallel with a CD4 count. Already in 1995 it was shown that artesunate reduced humoral immunity, reduced phagocytosis and increased the weight of spleen.
Lin PY, Feng ZM, Pan JQ, Zhang D, Xiao LY. Effects of artesunate on immune function in mice. Zhongguo Yao Li Xue Bao. 1995 Sep;16(5):441-4.
Artesunate stimulates the immune system at low doses and inhibits it at high doses (US Patent 5578637 H. Lai). The doses prescribed by WHO in ACTs are 100 times higher than the LD50. Wouldn’t it be preferable to give the immune system some initial help and then let it take over and deal with resistant parasites? Even in the absence of any clinical treatment, it can cure most of the malaria episodes in 10 days
Artemisia annua and Artemisia afra tea however contain many substances stimulating the immune system, like polyphenols, scopoletin, polysaccharides, proanthocyanidins, pentacyclic triterpes, fatty acids, saponins, phytosterols, amino acids, Arginine for example. Among all amino acids arginine has the specific ability to enhance NO production and inactivation of gametocytes. Nitric oxide is a known mediator of parasite killing by white blood cells as was shown when the production of NO by arginine is blocked by an inhibitor.
T Naotunne, ND Karunaweera, KN Mendis. Cytokine-mediated inactivation of malarial gametocytes is dependent on the presence of white blood cells and involves reactive nitrogen intermediates. Immunology 1993 78. 555-562
Another irresponsible guideline is that WHO still recommends in areas of stable malaria transmission intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine (SP). This may create situations worse than the persistence and recrudescence of gametocytemia noticed for artesunate.
Several recent studies show dramatic failure rates for SP-IPTp. In Malawi a recrudescence of 33% after PCR correction was noticed. 95% of the women with asymptomatic parasitaemia carried a quintuple mutant and the survival rate of the malaria infected primigravidae remained disastrous despite the treatment.
Julie Gutman, Dyson Mwandama, Ryan E Wiegand, Joseph Abdallah, Nnaemeka C Iriemenam, In vivo efficacy of sulphadoxine-pyrimethamine for the treatment of asymptomatic parasitaemia in pregnant women in Machinga District, Malawi. Malaria Journal 201514:197. DOI: 10.1186/s12936-015-0710-7
Since many years it is well known that pyrimethamine-sulfadoxine (SP) even increases the gametocyte density. In a trial in South Africa the duration of gametocyte carriage increased from 3 to 22 weeks between 1998 and 2002. Worse even, a 5-fold increase in gametytogenesis in Plasmodium falciparum has been documented for chloroquine in vitro. This higher transmission of gametocytes to Anopheles after chloroquine treatment was also documented in in vivo studies.
S. Enosse G.A. Butcher G. Margos J. The mosquito transmission of malaria: the effects of atovaquone-proguanil (Malarone™) and chloroquine. Transactions of The Royal Society of Tropical Medicine and Hygiene, 2000, Volume 94, Issue 1, 1
Buckling A, Read AF. Chloroquine increases Plasmodium falciparum gametocytogenesis in vitro. Parasitology, 1999, 118, 339-46
Karen I. Barnes, Francesca Little, Aaron Mabuza, and Nicholas J. White Increased Gametocytemia after Treatment: An Early Parasitological Indicator of Emerging Sulfadoxine-Pyrimethamine Resistance in Falciparum Malaria. J Infect Diseases, 2008, 197, 1605-1613
Harijani Ardi Marwoto, Gametocyte production in patients of Plasmodium falciparum malaria treated with Fansidar. Bul Penelit Kesehat, 1986 14 (1).
The persistence of WHO recommending SP might lead to an exponential increase of malaria in Africa. It is even less understandable as it is well known that this drug is life threatening for G6PD patients, not recommended for pregnant women as the effect on newborns is not known and it has many severe side effects. There is renewed acknowledgement that integrated control of gametocytemia is essential for elimination efforts. Plasmodium falciparum gametocytes are relatively insensitive to many anti-malarials and circulate for a longer period of time than gametocytes of other malaria species.
In a weakened immune system, parasites multiply to extremely high densities. This pool of parasites contains a larger number of mutants, upping the chances of some having greater virulence potential.
Elizabeth Pennisi. Weak Immune System? Malaria Doesn't Care. Science, Jul. 5, 2013
Owing to the fact that the host’s overall immune status has an influence on the virulence of the micro-organism, it is possible for a parasite to live within a host without ill effect. It may do so as a benign commensal until host defenses begin to diminish or are challenged by other factors such as increased exposure to other toxins, by poor nutrition or lifestyle factors, or by elements that compromise the immune capacity of the host.
A recent paper shows that in the face of Plasmodium falciparum re-exposure, children acquire exposure dependant immunoregulatory responses that dampen pathogenic inflammation while enhancing anti-parasite effector mechanisms. These data provide mechanistic insight into the observation that P falciparum infected children in endemic areas are often afebrile and tend to control parasite replication.
Portugal S, Moebius J, Skinner J, Doumbo S, Doumtabe D, Kone Y, et al. (2014) Exposure-Dependent Control of Malaria-Induced Inflammation in Children. PLoS Pathog 10(4): e1004079.
It is common knowledge that anything which leads to a depressed immune system (repeated malaria episodes, pregnancy, HIV, malnutrition, immune suppressing drugs…) will lead to a higher Plasmodium load in the infected person. The easiest way, although incomplete, to assess immunosuppression is the CD4 count.
Miriam K. Laufer, Joep J. G. van Oosterhout, Philip C. Thesing, Feston Thumba, Eduard E. Zijlstra, Stephen M. Graham, Terrie E. Taylor and Christopher V. Plowe. Impact of HIV-Associated Immunosuppression on Malaria Infection and Disease in Malawi. J Inf Dis., 2006, 193, 872-878
Michael O. Iroezindu, Emmanuel I. Agaba , Association of HIV-induced immunosuppression and clinical malaria in Nigerian adults, Afr. J. Infect. Dis. (2012) 6(2): 48 – 53
With a CD4 cell count of 200-500 cells /µL a 3fold higher incidence of clinical malaria and for a cell count < 200 cells/µL a 4.4 x higher compared to individuals with a cell count > 500 cells /µL. More intriguing is the fact that several recent papers have shown that in patients with low CD4 count it was impossible to lower the high Plasmodium load to zero with antimalarial treatment, even with the strongest drug known: dihydroartemisinin
Kirinyet J. K., Esamai, F. O., Magambo, J. K., Mkoji, G. M. Effect of HIV Infection on Anti-Malarial Treatment Outcome Among in Patients at the Moi Teaching and Referral Hospital, Eldoret, Kenya. International Journal of Advanced Research (2013), Volume 1, Issue 3, 140-149
Shah SN, Smith EE, Obonyo CO, Kain KC, HIV immunosuppression and antimalarial efficacy: sulfadoxine-pyrimethamine for the treatment of uncomplicated malaria in HIV-infected adults in Siaya, Kenya. J Infect Dis. 2006 Dec 1;194(11):1519-28.
Y.M. Tatfenga, J.C. Ihongbeb, M. Okoduab, F. Oviasogiec, J. Isiborb, CD4 count, viral load and parasite density of HIV positive individuals undergoing malaria treatment with dihydroartemisinin in Benin City, Edo state, Nigeria J Vect Borne Dis 44, June 2007, pp. 111–115
After a malaria attack the CD4 count remains low for several months in persons which had a low CD4 baseline at the moment of the infection. In endemic areas these persons are a pool for recrudescence, reinfection and transmission.
Current antimalarial drugs cure malaria or prevent infections but lack a sustained public health impact, because they fail to expedite the acquisition of protective immunity. Boosting the immune system becomes eventually more important in the fight against malaria than reducing the parasite count with a strong antimalarial drug.
IFBV-BELHERB and its partners in Katanga have been able to show that Artemisia annua and Artemisia afra raise CD4 and reduced parasitemia of malaria infected patients to 0 on day 11 in 95% of the cases.
Constant Kansango Tchandema, Pierre Lutgen In Vivo Trials on The Therapeutic Eﬀects of Encapsulated Artemisia Annua and Artemisia Afra. GJRA Global Journal for Research analysis 2016 June, ISSN No2277-8160
In a more recent paper it was shown that Artemisia plants completely eliminated the presence of gametocytes after 7 days of treatment. The efficiency was equivalent for Artemisia annua and Artemisia afra. Similar results on gametocyte elimination had already been observed in Mozambique by B Agosthino in 1998 and in other small trials across Africa. Unfortunately, these results have not been published because their tremendous importance had been underestimated.
J Munyangi, L Cornet-Vernet, P Lutgen, Int J Clin Res Trials 2016, 1: 109 http://dx.doi.org/10.15344/ijcrt/2016/109
A recent report of the Worldwide Antimalarial Resistance Network (WWARN Gametocyte Study Group, BMC Medicine 2016, 14:79), based on some 160 published studies, highlights the strong association of gametocytaemia with recrudescent infections and new infections warns against a simplistic comparison of treatment regimens based on gametocytaemia shortly after treatment. Initial treatment efficacy and post-treatment prophylaxis that postpones new infection, and therefore de novo gametocyte production, are important determinants of the impact of ACT regimens on malaria transmission.
This review which analyzed data from nearly 50,000 patients from trials that included measures of gametocytaemia by blood smears, found that he prevalence of gametocytaemia before and after treatment was greatest in young patients, and those with lower asexual parasite density, anaemia and absence of fever.
Harin A. Karunajeewa and Ivo Mueller. How important is gametocyte clearance after malaria therapy?BMC Medicine201614:93DOI: 10.1186/s12916-016-0641-3
Standard anti-malarial drug efficacy and drug resistance assessments neglect the gametocyte parameters in their protocols. With the spread of drug resistance and the absence of clinically proven vaccines, the use of gametocytocidal drugs or drug combinations with transmission-blocking activity is a high priority for malaria control and elimination.
Rashad Abdul-Ghani, Leonardo K. Basco, John C. Beier and Mohammed A. K. Mahdy Inclusion of gametocyte parameters in anti-malarial drug efficacy studies: filling a neglected gap needed for malaria elimination. Malaria Journal201514:413 DOI: 10.1186/s12936-015-0936-4
Based on the clinical trial results from RDCongo (op.cit.) Artemisia annua and Artemisia afra tea infusions definitely fulfill this requirement
Techniques to study the gametocyte load after antimalarial treatment had lost their priority over the years because all treatments (quinine, chloroquine, sukphadoxine-pyrimethamine…) anyway left a more or large gametocyte load. Such techniques had been developed more than 70 years ago.
NJ Serlin, JR Lisa. A concentration technic for gametocytes of estivo-autumnal malaria. City Hospital N.Y, 1940
Gametocytes were already discovered by Laveran in 1880, But we have not made much progress in understanding their genesis, not in 1935 and not in 2018,
JG Thompson A Robertson, The structure and development of Plasmodium falciparum gametocytes in internal organs and peripheral circulation. Transactions of the Royal Society of Tropical Medicine and Hygiene. Vol XXIX. No. 1. June, 1935.
One of the special features of Plasmodium falciparum gametocytes is that they have a much larger life span of infective stage: 2.5 days vs only 5 hours for Plasmodium knowlesi, berghei or chabaudi.
P Gautret, A Motard, Periodic infectivity of Plasmodium gametocytes to the vector, Parasite, 1999, 6, 103-111.
Smalley ME, Sinden RE. Plasmodium falciparum gametocytes: their longevity and infectivity. Parasitology. 1977 Feb;74(1):1-8.