Prevalence and temporal changes of mutations linked to anti-malarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Palawan, Philippines

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Plasmodium falciparum and Plasmodium vivax isolates from the Philippines were analysed.

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Varying mutations were found in markers linked to resistance to antimalarial drugs.

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None of the mutations were particularly of high prevalence.

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Clear temporal patterns in these mutations were observed within the past 15 years.

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Decrease in pfcrt and pfmdr mutations are in line with antimalarial policy change.

Objective

This study provides 2016 data on the prevalence of key single nucleotide polymorphisms (SNPs) associated with antimalarial drug resistance in Palawan, Philippines. Findings were combined with historical data to model temporal changes in the prevalence of these SNPs in Plasmodium isolates.

Methods

Plasmodium isolates were genotyped using drug resistance markers pfmdr1, pfcrt, pfdhfr, pfdhps, kelch-13, pvmdr1, pvdhfr, and pvdhps. Temporal trends in the probability of mutations were estimated as a function of time using a binomial generalised linear model.

Results

All samples sequenced for Plasmodium falciparum chloroquine markers pfmdr1 and pfcrt had wild-type alleles. Varying mutation patterns were observed for the sulphadoxine/pyrimethamine markers pfdhps and pfdhfr; complete quintuplet mutations were not found. No SNPs were observed for the artemisinin marker kelch-13. For Plasmodium vivax, differing patterns were detected for pvmdr1, pvdhfr, and pvdhps.

Conclusions

The study findings suggest that the current drugs remain effective and that there is limited importation and establishment of resistant parasites in the area. Clear temporal trends were recognised, with prominent decreases in the proportions of pfcrt and pfmdr mutations detected within the past 15 years, consistent with a change in antimalarial drug policy. Continuous surveillance of antimalarial drug resistance is important to support malaria elimination efforts.