Monitoring antifolate resistance in intermittent preventive therapy for malaria.

Mutations in the Plasmodium falciparum genes Pfdhfr and Pfdhps have rendered sulfadoxine-pyrimethamine (SP) ineffective for malaria treatment in most regions of the world. Yet, SP is efficacious as intermittent preventive therapy in pregnant women (IPTp) and infants (IPTi) and as seasonal malaria control in children (SMC). SP-IPTp is being widely implemented in sub-Saharan Africa. SP-IPTi is recommended where the prevalence of SP-resistant malaria parasites is low, whereas SMC is recommended for areas of intense seasonal malaria transmission. The continuing success of these interventions depends largely on the prevalence of Pfdhfr and Pfdhps resistance mutations in the target population. Here we review the relationship between resistance mutations and SP-IPT within target populations in the context of monitoring and informing implementation of this intervention.