Distinguishing Plasmodium falciparum treatment failures from re-infectionsby using polymerase chain reaction genotyping in a holoendemic area in northeastern Tanzania

An in vivo drug sensitivity study was conducted in Magoda village in northe astern Tanzania to evaluate the usefulness of polymerase chain reaction (PC R)-based genotyping of Plasmodium falciparum parasites to distinguish betwe en re-infection and treatment failure. The study tested P. falciparum susce ptibility to a combination of sulfadoxine/pyrimethamine (Fansidar(R); F. Ho ffmann La Roche, Basel, Switzerland). Blood samples were collected before t reatment and on days 7, 14, or 28 post-treatment in 51 asymptomatic childre n, of which 26 could not clear parasitemia within seven days post-treatment . Among the remaining 25 children who had no detectable parasites on day 7, only five remained parasite negative up to day 28. Primary and recrudescen t P. falciparum parasites were analyzed by PCR using family specific primer s for merozoite surface protein-1 (MSP-1), MSP-2, and glutamate-rich protei n (GLURP). All samples contained multiple P. falciparum infections. For all children with recrudescent P. falciparum, common alleles were detected in both the primary and recrudescent samples. However, in no child were the ex act same alleles detected in both samples, indicating that probably at leas t some of the recrudescing parasites originated from new infections. The st udy demonstrates the general usefulness of PCR genotyping technique in dist inguishing re-infections from true recrudescences following therapeutic dru g treatment.