ABSTRACT
Artemisinin Combination Therapies (ACT) stand as the most potent antimalarial treatments. In response to the emergence of ACT-resistant malaria parasites in Southeast Asia, the World Health Organization (WHO) has recommended continuous monitoring of the effectiveness of ACT and other antimalarials. To address this need, we collected dried blood spots from malaria patients during a 42-days drug efficacy trial evaluating the efficacy of Artesunate plus Amodiaquine (ASAQ), Artemether Plus Lumefantrine (AL) and Dihydroarthemisinine plus Piperaquine (DHAPQ) on simple P. falciparum malaria in 2017. Blood samples were collected on Day 0, prior to the patients' initial ACT dose, and on any days of recurrent parasitemia. Genetic markers such as Merozoite Surface Protein 1 (MSP1) and Merozoite Surface Protein 2 (MSP2) were genotyped to differentiate between recrudescence and re-infestation cases. Furthermore, PCR Single Specific Oligonucleotide Probes combined with-ELISA platform (PCR-SSOP-ELISA) and PCR-RFLP techniques were used to identify Pfcrt 72-76 mutant haplotype and Pfmdr1_86Y allele associated with chloroquine and amodiaquine resistance, respectively. Out of the 320 patients enrolled in the study, only 43 (13.43%) experienced relapses. Upon PCR correction, our analysis revealed that recrudescent infections affected 13 patients, with 8 in the ASAQ group, 5 in the AL group, and none in the DHAPQ group. Notably, no early treatment failures (within the first 3 days of treatment) were observed, and all recurrences occurred between Day 21 and Day 42. The prevalence of the Pfcrt wild-type haplotype CVMNK and Pfmdr N86 allele was 67.03% and 97.70%, respectively. In contrast, the mutant types CVIET and 86Y were found at 32.97% and 2.3%, respectively. The high prevalence of the CVMNK wild haplotype suggests that the parasites remain sensitive to chloroquine, while the low prevalence of the 86Y mutants indicates continued effectiveness of amodiaquine. Furthermore, the low prevalence of strains exhibiting the combination of CVIET and 86Y suggests that the use of multiple antimalarials is valuable for resistance control. Notably, none of the relapse cases carried the 86Y mutation or the combination of 86Y and CVIET.
