Studies on Genetic Mutations in Plasmodium Falciparum Strains Associated With 4- Aminoquinolines (Chloroquine) and Pyrimethamine Sulphadoxine (Fansidar) Resistance in Ghanaian Malaria Patients.

Abstract

The malaria drug policy for Ghana is chloroquine, Fansidar and quinine as the first line, second line and third line drugs respectively. However, the burden of malaria has been complicated by the emergence of resistance especially to chloroquine, which is a cheap and effective drug. It has therefore become imperative that the levels of resistance of Plasmodium falciparum to anti-malarial drugs (chloroquine and Fansidar) in Ghana be established and the information used to develop an appropriate drug policy for effective case management. This present study therefore used molecular techniques, mostly, polymerase chain reaction (PCR) to detect and characterise mutations in the putative P. falciparum transporter gene (pfcrt) and P. falciparum multi-drug resistance gene (pfmdrl) that are known from previous studies to be associated with chloroquine resistance. Mutations in the dihydrofolate reductase g ene ( dhfr) and dihydropteroate synthase gene (dhps) that are associated with pyrimethamine-sulphadoxine (Fansidar) resistance were also studied. Children aged 5 years and below diagnosed as having uncomplicated malaria were recruited at two sentinel hospitals in Ghana (Hohoe and Navrongo) for the study with an informed consent from parents or guardians. Blood films obtained from the patients were examined for the presence of malaria parasites before treatment (Day 0) and then on Days 7 and 14 after treatment. Filter paper blood blots were also obtained at the same time, for use in PCR to detect the mutations. In addition to these, in-vitro chloroquine sensitivity test was performed on P. falciparum isolates from 26 patients. The in vivo studies revealed that 62% and 31 % of the patients from Hohoe and Navrongo respectively were resistant to chloroquine. The classification of resistance according to parasitological clearance at Hohoe was 55%, 33% and 13% for RI, RII and RIII levels respectively; it was 43%, 33% and 23% respectively at Navrongo. T he b aseline p revalence o f t he p fc r t 76 and p fm d rl 86 mutations were 82.5% and 82.0% in Hohoe and 43.8% and 61.5% in Navrongo. An association between pfcrt and p fm d r l mutations and clinical outcome was observed a t Hohoe (odds ratio = 12.40, p = 0.0001) but not at Navrongo (odds ratio = 1.16, p = 0.75). The baseline prevalence of the quintuple mutations of dhfr and dhps were 31.1% and 1.04% for Hohoe and Navrongo respectively. The in-vitro results showed that 7 of the 26 isolates were resistant to chloroquine with an IC50 value of 1.5xl0'6 mol/litre. The results from this study suggest that mutations in pfcrt and p fm d rl can be used to predict the outcome of chloroquine treatment at Hohoe but not at Navrongo. The observed differences in the pfcrt and pfmdrl prevalence rates and in the association between genetic mutations and treatment outcome, is thought to be due to differences in drug pressure at the two areas. The relatively high prevalence of the quintuple mutations of dhfr and dhps observed at Hohoe gives an idea of the use of Fansidar whilst is the contrary for Navrongo.