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Sulfadoxine-pyrimethamine (SP) is still a useful drug to combat chloroquine-resistant Plasmodium falciparum malaria in Cameroon. Because of several disadvantages of the in vivo test and in vitro drug sensitivity assays, molecular assays are an alternative laboratory tool to monitor the evolution of antifolate resistance, especially over the entire country that is characterized by several epidemiologic strata and malaria transmission patterns. In this study, 1,430 blood samples from either symptomatic children or asymptomatic carriers were collected from 14 sites throughout the country between 1999 and 2003 for the analysis of dihydrofolate reductase (dhfr) sequence. Of 1,368 samples (95.7%) that were successfully amplified, 1,180 were analyzed by direct sequencing of the polymerase chain reaction product, and 188 were analyzed by restriction enzymes. The prevalences of the wild-type, single Asn-108 mutation, double Arg-59/Asn-108 mutations, double Ile-51/Asn-108 mutations, triple Ile-51/Arg-59/Asn-108 mutations, and mixed alleles were 20.8%, 2.8%, 5.7%, 0.8%, 62.2%, and 7.6%, respectively. The proportions of triple dhfr mutations were > 60% at all study sites, with the exception of the eastern province (42% triple mutants in Bertoua in 1999) and the northern provinces (11–35% triple mutants in Ngaoundere, Garoua, and Maroua). In these two provinces, the proportion of mutant parasites increased significantly (P < 0.05) over the period of 2–4 years. Furthermore, there was a higher proportion (P < 0.05) of wild-type parasites in the northern provinces, compared with the rest of the country. The geographic mapping of molecular markers offers a novel tool for monitoring the epidemiology of drug-resistant malaria.
Received October 24, 2005. Accepted for publication May 3, 2006.
Acknowledgments: The authors thank the personnel of dispensaries and hospitals for their aid in recruiting patients.
Financial support: This study was supported by the French Ministry of Research (Programme PAL+).
* Address correspondence to Leonardo Basco, OCEAC, B. P. 288, Yaoundé, Cameroon (Central Africa). E-mail: lkbasco{at}yahoo.fr
Authors’ addresses: Rachida Tahar, Leonardo K. Basco, Unité de Recherche "Paludologie Afrotropicale," Institut de Recherche pour le Développement (IRD)—Laboratoire de Recherche sur le Paludisme, OCEAC, B. P. 288, Yaoundé, Cameroon.
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