Surveillance of molecular markers of Sulphadoxine-Pyrimethamine resistance in Ghana after the change of malaria treatment policy

Abstract

In Ghana, sulphadoxine-pyrimethamine (SP) is used as intermittent preventive treatment in pregnant women (IPTp) since 2005. Before then, it was the second-line drug for the treatment of uncomplicated malaria. SP is an over the counter drug for IPTp and thus may be available for use by others. Drug pressure enhances the spread of resistant parasites and it is therefore imperative to monitor molecular markers of Plasmodium falciparum antimalarial drug resistance for early detection of the development of resistance. This information in addition to in-vivo and in-vitro assessment of drug resistance is crucial for treatment policy amendment and for non-immune travelers in their choice of prophylactic antimalarials. We therefore characterized mutations in P. falciparum dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) for sulphadoxine- pyrimethamine (SP) resistance after the change in treatment policy in Ghana. 738 filter paper blood blots collected from 2005-2010 from children aged 6-59 months with uncomplicated malaria presenting to 9 existing sentinel sites for monitoring antimalarial drug resistance in Ghana were analyzed. PCR followed by restriction length polymorphism (RFLP) analysis was used to characterize mutations at codons 51, 59, 108, 164 of the dhfr gene and codons 436, 437 and 540 of the dhps gene. Data analysis included the determination of the prevalence of the mutations and the trend over the years. The overall trend showed an increase in the prevalence of the mutations from 2005-2010. The prevalence of the dhfr triple mutant (51, 59 and 108) was 29% for 2005-2006, 46% for 2007-2008 and 54% for 2010. No dhfr 164 mutant was observed in all the samples. The dhps double mutant (437 and 540) was 0.42%, 0.24% and 1.12% respectively for 2005-2006, 2007-2008 and 2010. For dhps double mutant (436 and 437) was 43%, 45% and 38% for 2005-2006, 2007-2008 and 2010 respectively. High prevalence of the 437 mutation (range: 59%-80%) was observed compared to low prevalence of the 540 mutant (0.24%-1,12%). The quintuple mutant (dhfr 51, 59, 108 and dhps 437, 540) was only observed in one of the 2010 samples. The study shows the effect of the continuous use of SP which enhances the selection and spread of resistant parasites in the country. Whether the use of SP alone for IPTp is justified will be further discussed.