Molecular Variation of Plasmodium Vivax Dehydrofolate Reductase in Mexico and Nicaragua Contrasts with That Occurring in South America

OBJECTIVE:To research mutations associated to pyrimethamine resistance in dihydrofolate reductase (pvdhfr) of Plasmodium vivax from Mexico and Nicaragua and compare it to that reported in the rest of America.MATERIALS AND METHODS:Genomic DNA was obtained from P. vivax-infected blood samples. A pvdhfr gene fragment was amplified and sequenced. The identified gene variations were compared to those observed in other affected sites of America.RESULTS:No mutations in pvdhfr were detected in P. vivax from Mexico and Nicaragua. One synonymous change and variation in the repeat domain was detected in Nicaraguan parasites. In South America, a high frequency of variant residues 58R and 117N associated to pyrimethamine resistance was reported.CONCLUSIONS:The lack of polymorphisms associated with pyrimethamine resistance suggests that drug-resistant P. vivax has not penetrated Mesoamerica, nor have local parasites been under selective pressure. These data contribute to establish the basis for the epidemiological surveillance of drug resistance.