Artemisinin resistance in Plasmodium falciparum

Abstract

Benoit Witkowski and colleagues1Witkowski B Amaratunga C Khim N et al.Novel phenotypic assays for the detection of artemisinin-resistant Plasmodium falciparum malaria in Cambodia: in-vitro and ex-vivo drug-response studies.Lancet Infect Dis. 2013; 13: 1043-1049Summary Full Text Full Text PDF PubMed Scopus (361) Google Scholar reported a simple and rapid in vitro method to detect artemisinin resistance of P falciparum. They show that the slow clearance of parasites by artemisinin combination therapies is a result of a drop in susceptibility among young ring form parasites whereas susceptibility is maintained in mature stages. However, the clinical relevance of this finding to treatment failure is unclear since these infections could still be successfully treated with artemisinin combination therapies. Experiences in China also suggest that such resistance could be overcome if the right strategies are used. In China, the recommended duration of monotherapy with artemisinin drugs for treatment of falciparum malaria—particularly the chloroquine-resistant strain—is 5–7 days.2The Ministry of Health of ChinaNational guideline for use and regimen of antimalarials.Chin J Parasit Dis Control. 2002; 15: 129-130Google Scholar A study of patients treated with dihydroartemisinin (60 mg) daily (120 mg on day 1) for 3, 5, or 7 days showed no recrudescences in the 7 day group, compared with recrudescence in 66% of patients in the 5 day group and 52% in the 3 day group. Therefore, it was recommended that the 7 day course, with a total dose of 480 mg of dihydroartemisin, is the optimum regimen for treatment of P falciparum infection.3Fu LC Guo XB Wang WL et al.An exploration on the dosage and treatment course of dihydroartemisinin for falciparum malaria.Trad Chin Drug Res Clin Pharm. 1996; 7: 17-18Google Scholar Another feature of clinical malaria management in China is the quarantine of patients during treatment to prevent transmission and hamper the spread of resistance. Combination of artemisinin drugs with other antimalarial treatments gives more effective treatment at the early stage of malaria infections, although, it is becoming clear that the number of treatment days has a major impact on efficacy of artemisinin treatment either as monotherapy or in combination, especially if ineffective partner drugs are used.4Ferreira PE Culleton R Gil JP Meshnick SR Artemisinin resistance in Plasmodium falciparum: what is it really?.Trends Parasitol. 2013; 29: 318-320Summary Full Text Full Text PDF PubMed Scopus (33) Google Scholar Although we do not have evidence to demonstrate this hypothesis so far, increasing the duration of artemisinin treatment and use of efficacious partner drugs could sustain the efficacy of artemisinin combination therapies. We declare no competing interests. Novel phenotypic assays for the detection of artemisinin-resistant Plasmodium falciparum malaria in Cambodia: in-vitro and ex-vivo drug-response studiesThe in-vitro RSA of 0–3 h ring-stage parasites provides a platform for the molecular characterisation of artemisinin resistance. The ex-vivo RSA can be easily implemented where surveillance for artemisinin resistance is needed. Full-Text PDF