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

Abstract

Abstract. An in vivo drug sensitivity study was conducted in Magoda village in northeastern Tanzania to evaluate the usefulness of polymerase chain reaction (PCR)-based genotyping of Plasmodium falciparum parasites to distinguish between re-infection and treatment failure. The study tested P. falciparum susceptibility to a combination of sulfadoxine/pyrimethamine (Fansidar; F. Hoffmann La Roche, Basel, Switzerland). Blood samples were collected before treatment and on days 7, 14, or 28 post-treatment in 51 asymptomatic children, 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 recrudescent P. falciparum parasites were analyzed by PCR using family specific primers for merozoite surface protein-1 (MSP-1), MSP-2, and glutamate-rich protein (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 exact same alleles detected in both samples, indicating that probably at least some of the recrudescing parasites originated from new infections. The study demonstrates the general usefulness of PCR genotyping technique in distinguishing re-infections from true recrudescences following therapeutic drug treatment.

Declining burden of malaria over two decades in a rural community of Muheza district, north-eastern Tanzania

“…Patients not symptomatically treated but with malaria parasites in blood smears, were given antimalarials on the following day after microscopy results were obtained. Furthermore, repeated in vivo drug efficacy trials were carried out and involved patients with uncomplicated malaria (confirmed by microscopy) in 1994–1996 [43-45], 1997 [46] and 1998–1999 [38] testing SP, and later AQ in 2003 [47]. In December 1998, each sleeping bed in all households in Magoda (on request from the villagers), received a permethrin-treated net (ITN) while in Mpapayu, deltamethrin-treated nets were distributed in March 2001; all ITNs were re-impregnated twice a year [38] until 2003.…”

Dihydrofolate Reductase and Dihydropteroate Synthase Genotypes Associated With in Vitro Resistance of Plasmodium Falciparum to Pyrimethamine, Trimethoprim, Sulfadoxine, and Sulfamethoxazole

“…This is not surprising because polyclonal infections of parasites differing in their susceptibility to drugs commonly are found in natural infections of P. falciparum. 21 The difference in IC 50 values of isolates with wild or mutant genotype was 16-fold for TRM and 100-fold for PYR. Based on these findings, it seems that additional mutations are needed to confer higher resistance to TRM.…”

Genetic Diversity and Allelic Frequency of Glutamate-Rich Protein (GLURP) inPlasmodium falciparumIsolates from Sub-Saharan Africa

“…Polymerase chain reaction (PCR) genotyping methods, utilizing nested allelic type-specific amplification of surface proteins, have become mainstays in this field. These tools have facilitated the definition of allelic variability in an individual or within a population to deconvolute recurrent or recrudescent infection, as well as to clarify effectiveness of prescribed therapy or drug resistance 8–11. It is an important investigative tool to delineate effectiveness of therapeutic agents during clinical trials or efficacy studies.…”