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Open Access Research

The usefulness of twenty-four molecular markers in predicting treatment outcome with combination therapy of amodiaquine plus sulphadoxine-pyrimethamine against falciparum malaria in Papua New Guinea

Jutta Marfurt13, Ivo Müller2, Albert Sie2, Olive Oa24, John C Reeder25, Thomas A Smith16, Hans-Peter Beck17 and Blaise Genton18*

Author Affiliations

1 Swiss Tropical Institute, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland

2 Papua New Guinea Institute of Medical Research, Goroka, P.O. Box 60, EHP 441, Papua New Guinea

3 Menzies School of Health Research, P.O. Box 41096, Casuarina, Darwin, NT 0811, Australia

4 Papua New Guinea Institute of Medical Research, Maprik, P.O. Box 400, ESP 533, Papua New Guinea

5 International Health Research Strategy, Burnet Institute for Medical Research and Public Health, P.O. Box 2284, Melbourne VIC 2001, Australia

6 Swiss Tropical Institute, Department of Public Health and Epidemiology, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland

7 Swiss Tropical Institute, Department of Medical Parasitology and Infection Biology, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland

8 Ifakara Health Research & Development Centre, P.O. Box 78373, Dar es Salaam, Tanzania

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Malaria Journal 2008, 7:61  doi:10.1186/1475-2875-7-61

Published: 19 April 2008

Abstract

Background

In Papua New Guinea (PNG), combination therapy with amodiaquine (AQ) or chloroquine (CQ) plus sulphadoxine-pyrimethamine (SP) was introduced as first-line treatment against uncomplicated malaria in 2000.

Methods

We assessed in vivo treatment failure rates with AQ+SP in two different areas in PNG and twenty-four molecular drug resistance markers of Plasmodium falciparum were characterized in pre-treatment samples. The aim of the study was to investigate the association between infecting genotype and treatment response in order to identify useful predictors of treatment failure with AQ+SP.

Results

In 2004, Day-28 treatment failure rates for AQ+SP were 29% in the Karimui and 19% in the South Wosera area, respectively. The strongest independent predictors for treatment failure with AQ+SP were pfmdr1 N86Y (OR = 7.87, p < 0.01) and pfdhps A437G (OR = 3.44, p < 0.01). Mutations found in CQ/AQ related markers pfcrt K76T, A220S, N326D, and I356L did not help to increase the predictive value, the most likely reason being that these mutations reached almost fixed levels. Though mutations in SP related markers pfdhfr S108N and C59R were not associated with treatment failure, they increased the predictive value of pfdhps A437G. The difference in treatment failure rate in the two sites was reflected in the corresponding genetic profile of the parasite populations, with significant differences seen in the allele frequencies of mutant pfmdr1 N86Y, pfmdr1 Y184F, pfcrt A220S, and pfdhps A437G.

Conclusion

The study provides evidence for high levels of resistance to the combination regimen of AQ+SP in PNG and indicates which of the many molecular markers analysed are useful for the monitoring of parasite resistance to combinations with AQ+SP.