Mutations within folate metabolising genes of Plasmodium falciparum in Cameroon.

Abstract

Sulfadoxine-Pyrimethamine (S-P) still used in some parts of the country was suggested as the second line drug to amodiaquine following widespread failure of chloroquine in Cameroon in 2002. We investigated the efficacy of S-P and determined the baseline mutations on marker genes for folate metabolism (dhfr anddhps) in the forest and Guinea-Savanna ecozones of Cameroon, as a way of tracking resistance in patients aged between 0.5 and 10 years in Limbe (n=138), Nkambe (n=103), Fontem (n=100 ) and Dschang (n=93 ). Filter paper blood sample were collected prior to treatment and on clinical failure days to determine the prevalence of molecular markers of resistance and to assess the mutation rates on the folate metabolising genes by restriction fragment length polymorphism assays or dot-blot assays with 32-P labeled mutation-specific probes. Sequencing using the dideoxy-chain termination method by PCR was conducted to confirm doubtful cases. Late parasitological failure (LPF) was higher in Limbe (30.6%) compared to Nkambe 10.3% (p=0.001). The prevalence of the 437-Gly mutation though lower in Nkambe, 57.6%, than in Limbe, 60% were statistically not different (p=0.2). All genotypes with the 108N mutation also carried the 51-Ile and 59-Arg mutations. All sensitive alleles (S108) also carried the amino acids, 51-Asn and 59-Cys. S-P is no longer efficacious in Limbe and Nkambe, Cameroon for treating uncomplicated malaria in children below 10 years. Instead 437G rather than the 108 N of Plasmodium falciparum may be determinant as the marker for tracking the spread of S-P resistance in Cameroon. Key words: Mutations, plasmodium, sulfadoxine-pyrimethamine, resistance, dhfr,dhps