Drug Resistance of Imported P. falciparum and P. vivax Isolates - China, 2021-2023

Artemisinin-based combination therapies (ACTs) remain the first-line treatment for uncomplicated malaria caused by P. falciparum, while chloroquine (CQ) serves as the primary treatment for P. vivax. However, the global spread of antimalarial drug resistance has become an increasing concern over time.

The integrated drug efficacy studies (iDES) demonstrated that artesunate (AS) plus dihydroartemisinin-piperaquine (DHA-PPQ) and chloroquine (CQ) remain effective first-line treatments for P. falciparum and P. vivax malaria, respectively. However, the occurrence of late treatment failure (LTF) and day 3 (D3) parasite positivity following treatment, suggests decreasing therapeutic efficacy. Molecular surveillance of P. falciparum resistance revealed novel mutation sites in pfK13 (S459T, N499T, A578S, and V692L) in addition to the previously reported F446I, P574L, and C580Y mutations. Concurrently, the difference in mutation patterns between pfcrt and pfmdr1 was significant (P<0.01), with the Y184F locus of the multidrug resistance gene pfmdr1 showing the highest mutation frequency at 40.5% of cases.

The iDES and molecular surveillance of antimalarial drug resistance indicated decreasing sensitivity to current first-line treatments. Continued surveillance of antimalarial drug resistance is vital for early warning and appropriate response to the spread of resistant parasites.