Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

BackgroundResistance to anti-malarials is a serious threat to the efforts to control and eliminate malaria. Surveillance based on simple field protocols with centralized testing to detect molecular markers associated with anti-malarial drug resistance can be used to identify locations where further investigations are needed.MethodsDried blood spots were collected from 398 patients (age range 5-59 years, 99% male) with Plasmodium falciparum infections detected using rapid diagnostic tests over two rounds of sample collection conducted in 2016 and 2017 in Komé, South-West Chad. Specimens were genotyped using amplicon sequencing or qPCR for validated markers of anti-malarial resistance including partner drugs used in artemisinin-based combination therapy (ACT).ResultsNo mutations in the pfk13 gene known to be associated with artemisinin resistance were found but a high proportion of parasites carried other mutations, specifically K189T (190/349, 54.4%, 95%CI 49.0-59.8%). Of 331 specimens successfully genotyped for pfmdr1 and pfcrt, 52% (95%CI 46.4-57.5%) carried the NFD-K haplotype, known to be associated with reduced susceptibility to lumefantrine. Only 20 of 336 (6.0%, 95%CI 3.7-9.0%) had parasites with the pfmdr1-N86Y polymorphism associated with increased treatment failures with amodiaquine. Nearly all parasites carried at least one mutation in pfdhfr and/or pfdhps genes but 'sextuple' mutations in pfdhfr-pfdhps including pfdhps -A581G were rare (8/336 overall, 2.4%, 95%CI 1.2-4.6%). Only one specimen containing parasites with pfmdr1 gene amplification was detected.ConclusionsThese results provide information on the likely high efficacy of artemisinin-based combinations commonly used in Chad, but suggest decreasing levels of sensitivity to lumefantrine and high levels of resistance to sulfadoxine-pyrimethamine used for seasonal malaria chemoprevention and intermittent preventive therapy in pregnancy. A majority of parasites had mutations in the pfk13 gene, none of which are known to be associated with artemisinin resistance. A therapeutic efficacy study needs to be conducted to confirm the efficacy of artemether-lumefantrine.

Original publication




Journal article


Malaria journal

Publication Date





Department of Molecular Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.


Humans, Plasmodium falciparum, Protozoan Proteins, Antimalarials, Drug Resistance, Polymorphism, Genetic, Adolescent, Adult, Middle Aged, Child, Child, Preschool, Chad, Female, Male, Young Adult, Artemether, Artemether, Lumefantrine Drug Combination