The Prevalence of plasmodium falciparum point mutations associated with resistance to chloroquine and artemisinin in Lusaka urban district

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Chaponda, Enesia Banda
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Malaria is the leading cause of morbidity and mortality in Zambia where 95 percent of the cases are caused by Plasmodium falciparum. Chloroquine, the former drug of choice for uncomplicated malaria treatment became less effective as a result of parasite resistance. Therefore in 2002, the Malaria Treatment Policy was revised to replace chloroquine with Coartem(R) as first line treatment for uncomplicated malaria except in children below 10 kilograms of body weight and pregnant women for which the drug is not registered. This decision was based on in vivo efficacy studies conducted in various sentinel sites around the country between 1995 and 2000. These studies showed treatment failure rates higher than 25 percent prompting the Government of the Republic of Zambia to change the Malaria Treatment Policy as recommended by the World Health Organization. Early and late treatment failure figures were summed up to obtain resistance rates. In 1996, the resistance figure for Lusaka Province represented by Chongwe district was determined at 43.4 percent. However the molecular epidemiology of the chloroquine resistance marker was not established. Therefore, there is still a need for base line information on the prevalence of the chloroquine resistance marker in Zambia. A point mutation at amino acid codon 76 of P. falciparum chloroquine resistance transporter (Pfcrt) gene is a molecular marker of resistance to chloroquine (Djimde et al. 2001). While a mutation in the sarco/endoplasrjjic reticulum calcium dependant Plasmodium falciparum adenosine triphosphatase6 (SERCA-PfATPase6) gene at nucleotide 2307 is the putative molecular marker of resistance to artemisinin (Jambou et al., 2005). The general objective of this study was to determine the prevalence of the P. falciparum point mutations associated with chloroquine and artemisinin resistance in Lusaka Urban district. The prevalence of the chloroquine and the artemisinin resistance markers was measured in a cross-sectional survey in Lusaka urban district. A total of 161 blood samples were collected from patients onto filter paper and air-dried. Parasite DNA was extracted by the chelex extraction method from air-dried filter papers. Nested polymerase chain reaction (PCR) followed by restriction enzyme digestion was carried out. The digestion products were analyzed by elecrophoresis on ethidium bromide stained 2 percent agarose gel and visualized under ultra-violet (UV) transillumination. Of 119 individuals interviewed in Lusaka Urban district 3 (2.5 percent) had used chloroquine for malaria after the withdrawal of chloroquine from health centres in Lusaka Urban District. The number of respondents that had taken Coartem® at the time of the study since its introduction in Zambia was 38 (31.9 percent). The Pfcrt K76T mutation was detected in 53.8 percent of the field samples assayed. The point mutation in the SERCA-ATPase6 associated with P. falciparum resistance to artemisinin was not detected in any of the samples. Coartem® is available both in health centres and drug stores in Lusaka Urban District. Chloroquine is no longer in stock in government health centres but is still in stock in some drug stores in Lusaka Urban District. The chloroquine-resistant K76T marker is still prevalent in Lusaka urban district five years after the malaria treatment policy was changed from the use of chloroquine to the use of Coartem® as first line treatment for uncomplicated malaria. The findings indicate that if the persistence of chloroquine-resistant P. falciparum malaria is to be avoided, the reintroduction of chloroquine, either as a monotherapy or in combination with other drugs, should not be considered at present. The SERCA-PfATPase6 mutation reported to be associated with P. falciparum resistance to artemisinin (Jambou et al., 2005) was not observed in this study. The absence of the artemisinin resistance mutation seems to suggest total P. falciparum sensitivity to artemisinin, unless a different resistance mechanism occurs in the area. This can therefore serve as a base-line for future monitoring of artemisinin sensitivity.
Medical Parasitology-Zambia , Molecular Parasitology-Zambia , Parasitism