Therapeutic efficacy of artesunate in the treatment of uncomplicated Plasmodium falciparum malaria and anti-malarial, drug-resistance marker polymorphisms in populations near the China-Myanmar border

Abstract

Background: The aim of this study was to evaluate the clinical outcome after seven-day artesunate monotherapy for uncomplicated Plasmodium falciparum malaria in Yingjiang County along the China-Myanmar border and investigate genetic polymorphisms in the P. falciparum chloroquine-resistance transporter (pfcrt), multidrug resistance 1 (pfmdr1), dihydrofolate reductase (pfdhfr), dihydropteroate synthase (pfdhps) and ATPase (pfatp6) genes.

Methods: Patients ≥ one year of age with fever (axillary temperature ≥37.5°C) or history of fever and P. falciparum mono-infection were included. Patients received anti-malarial treatment with artesunate (total dose of 16 mg/kg over seven days) by directly observed therapy. After a 28-day follow-up, treatment efficacy and effectiveness were assessed based on clinical and parasitological outcomes. Treatment failure was defined as recrudescence of the original parasite and distinguished with new infection confirmed by PCR. Analysis of gene mutation and amplification were performed by nested polymerase chain reaction.

Results: Sixty-five patients were enrolled; 10 withdrew from the study, and six were lost to follow-up. All but two patients demonstrated adequate clinical and parasitological response; 12 had detectable parasitaemia on day 3. These two patients were confirmed to be new infection by PCR. The efficacy of artesunate was 95.9%. The pfcrt mutation in codon 76 was found in all isolates (100%), and mutations in codons 71 and 72 were found in 4.8% of parasite isolates. No mutation of pfmdr1 (codons 86 or 1246) was found. Among all samples, 5.1% were wild type for pfdhfr, whereas the other samples had mutations in four codons (51, 59, 108 and 164), and mutations in pfdhps (codons 436, 437, 540 and 581) were found in all isolates. No samples had mutations in pfatp6 codons 623 or 769, but two new mutations (N683K and R756K) were found in 4.6% and 9.2% of parasite isolates, respectively.

Conclusion: Plasmodium falciparum infection was associated with slow parasite clearance and suspected artemisinin resistance at the China-Myanmar border area. The prevalence of pfcrt 76 T and markers for SP resistance are still high. It should be strengthened further on parasite clearance time or clearance half life to confirm the resistance status, and molecular epidemiology should provide complementary information to assess the appropriateness of current policies based on artemisinin derivatives.

Figure 1

The location of Yingjiang County relative to neighbouring countries.

Figure 2

Patient recruitment and clinical outcomes.

Figure 3

Average patient body temperature and parasite density on days 0, 1, 2, 3, 7, 14, 21 and 28 after artesunate treatment for seven days.

Figure 4

Frequency of pfdhfr and pfdhps haplotypes in samples from Yingjiang County.