Dynamics of pyrimethamine-resistant P. falciparum parasites in sulphadoxine-pyrimethamine treated Tanzanian children

A mutation -specific PCR assay was used to determine the dynamics of pyrimethamine-resistant P. falciparum parasites in sulphadoxine-pyrimethamine treated children, 0-5 years, from a village in Tanzania. The assay is based on the observation that a point mutation in the dihydrofolate reductase (DHFR) gene confers resistance to pyrimethamine. The PCR assay was used on blood samples collected from treated children on days 0,2,7,14,21and 28. Preliminary results revealed that pyrimethamine-sensitive parasites seemed to be completely cleared after 7 or 14 days of treatment but re-surfaced after 21 days. It was observed that in those children without mixed infection on day 0, pyrimethamine-resistant parasites appeared after 7 days. The implifications of these findings are discussed.