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      Rationale for recommending a lower dose of primaquine as a Plasmodium falciparum gametocytocide in populations where G6PD deficiency is common

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      1 , , 2 , 3 , 4
      Malaria Journal
      BioMed Central

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          Abstract

          In areas of low malaria transmission, it is currently recommended that a single dose of primaquine (0.75 mg base/kg; 45 mg adult dose) be added to artemisinin combination treatment (ACT) in acute falciparum malaria to block malaria transmission. Review of studies of transmission-blocking activity based on the infectivity of patients or volunteers to anopheline mosquitoes, and of haemolytic toxicity in glucose 6-dehydrogenase (G6PD) deficient subjects, suggests that a lower primaquine dose (0.25 mg base/kg) would be safer and equally effective. This lower dose could be deployed together with ACTs without G6PD testing wherever use of a specific gametocytocide is indicated.

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          Most cited references33

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          Emergence of artemisinin-resistant malaria on the western border of Thailand: a longitudinal study

          Summary Background Artemisinin-resistant falciparum malaria has arisen in western Cambodia. A concerted international effort is underway to contain artemisinin-resistant Plasmodium falciparum, but containment strategies are dependent on whether resistance has emerged elsewhere. We aimed to establish whether artemisinin resistance has spread or emerged on the Thailand–Myanmar (Burma) border. Methods In malaria clinics located along the northwestern border of Thailand, we measured six hourly parasite counts in patients with uncomplicated hyperparasitaemic falciparum malaria (≥4% infected red blood cells) who had been given various oral artesunate-containing regimens since 2001. Parasite clearance half-lives were estimated and parasites were genotyped for 93 single nucleotide polymorphisms. Findings 3202 patients were studied between 2001 and 2010. Parasite clearance half-lives lengthened from a geometric mean of 2·6 h (95% CI 2·5–2·7) in 2001, to 3·7 h (3·6–3·8) in 2010, compared with a mean of 5·5 h (5·2–5·9) in 119 patients in western Cambodia measured between 2007 and 2010. The proportion of slow-clearing infections (half-life ≥6·2 h) increased from 0·6% in 2001, to 20% in 2010, compared with 42% in western Cambodia between 2007 and 2010. Of 1583 infections genotyped, 148 multilocus parasite genotypes were identified, each of which infected between two and 13 patients. The proportion of variation in parasite clearance attributable to parasite genetics increased from 30% between 2001 and 2004, to 66% between 2007 and 2010. Interpretation Genetically determined artemisinin resistance in P falciparum emerged along the Thailand–Myanmar border at least 8 years ago and has since increased substantially. At this rate of increase, resistance will reach rates reported in western Cambodia in 2–6 years. Funding The Wellcome Trust and National Institutes of Health.
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            Epidemiology and infectivity of Plasmodium falciparum and Plasmodium vivax gametocytes in relation to malaria control and elimination.

            Malaria remains a major cause of morbidity and mortality in the tropics, with Plasmodium falciparum responsible for the majority of the disease burden and P. vivax being the geographically most widely distributed cause of malaria. Gametocytes are the sexual-stage parasites that infect Anopheles mosquitoes and mediate the onward transmission of the disease. Gametocytes are poorly studied despite this crucial role, but with a recent resurgence of interest in malaria elimination, the study of gametocytes is in vogue. This review highlights the current state of knowledge with regard to the development and longevity of P. falciparum and P. vivax gametocytes in the human host and the factors influencing their distribution within endemic populations. The evidence for immune responses, antimalarial drugs, and drug resistance influencing infectiousness to mosquitoes is reviewed. We discuss how the application of molecular techniques has led to the identification of submicroscopic gametocyte carriage and to a reassessment of the human infectious reservoir. These components are drawn together to show how control measures that aim to reduce malaria transmission, such as mass drug administration and a transmission-blocking vaccine, might better be deployed.
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              Effects of artemisinin derivatives on malaria transmissibility.

              On the western border of Thailand the efficacy of mefloquine in the treatment of falciparum malaria has declined while gametocyte carriage rates have increased, which suggests increased transmissibility of these resistant infections. We compared the following antimalarial drugs in relation to subsequent Plasmodium falciparum gametocyte carriage: mefloquine, halofantrine, quinine, and the artemisinin derivatives. Between 1990 and 1995 we assessed gametocytaemia in a series of prospective studies of antimalarial drug treatment in 5193 adults and children with acute uncomplicated falciparum malaria in an area of malarious hill forest on the western border of Thailand. Weekly parasite counts from thick and thin blood films were done during the 4-week (1990-93) or 9-week (1993-95) follow-up period. Gametocyte positivity rates and person gametocyte week (PGW) rates were calculated to measure gametocyte carriage and transmission potential. In primary P falciparum infections the gametocyte carriage rate was significantly higher after treatment with mefloquine than after treatment with the artemisinin derivatives (PGW 34.1 [95% CI 25.2-42.9] vs 3.9 [1.9-5.9] per 1000 person weeks; relative risk 8.0 [4.1-15.6]; p<0.0001). Recrudescent infections were associated with increased gametocyte carrier rates (relative risk 2.2 [1.6-3.0]; p<0.0001), but retreatment with artemisinin derivatives reduced subsequent gametocyte carriage 18.5 fold [3.5-98] compared with mefloquine retreatment and 6.8 fold (3.1-15.1) compared with quinine retreatment (p<0.001). The introduction of the artemisinin derivatives in routine treatment at this study site in mid 1994 was associated with a reduction in the subsequent incidence of falciparum malaria of 47 (25-69)% Although environmental changes affect vector numbers, and hence malaria incidence, artemisinin derivatives were found to reduce the transmission potential of falciparum malaria. Widespread introduction of artemisinin derivatives in the treatment of falciparum malaria may prevent the spread of multidrug resistance.
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                Author and article information

                Contributors
                Journal
                Malar J
                Malar. J
                Malaria Journal
                BioMed Central
                1475-2875
                2012
                14 December 2012
                : 11
                : 418
                Affiliations
                [1 ]Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
                [2 ]Research Centre for Qinghao, Guangzhou University of Chinese Medicine, Guangzhou, China
                [3 ]Jiangsu Institute of Parasitic Diseases, Wuxi, China
                [4 ]Istituto Toscano Tumori, Florence, Italy
                Article
                1475-2875-11-418
                10.1186/1475-2875-11-418
                3546849
                23237606
                ea65ca9a-e5a9-4ec6-80fe-6994c5faf530
                Copyright ©2012 White et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 14 October 2012
                : 28 November 2012
                Categories
                Review

                Infectious disease & Microbiology
                Infectious disease & Microbiology

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