| dc.description.abstract | In November of 2000, Uganda changed its anti-malarial policy to replace chloroquine (CQ) with a combination of CQ and sulphadoxine–pyrimethamine (SP) as the first line agents. The idea of the combination was to delay the development of malaria resistance to either drug when used alone. Information was limited on the efficacy of either drug yet SP resistance was increasing in East Africa. SP resistance has been associated with point mutations in Dihydrofolate reductase (DHFR) and Dihydopteroate Synthase (DHPS) in vitro, but correlations with in vivo outcomes are less clear. Four separate studies were done over a four-year period, to monitor and evaluate the rate of development of resistance using both clinical and molecular methods.
In 1999 in Kampala, Uganda, adults and children with uncomplicated falciparum malaria were treated with SP (1.25 mg/kg pyrimethamine, 25 mg/kg sulfadoxine) and assessed using WHO clinical and parasitological criteria. Analysis of DHFR/DHPS mutations was done using PCR and restriction endonuclease digestion methods. Clinical treatment failure was 11% at 14 days, increasing to 30% at 28 days, after excluding new infections. Mutations in DHFR 108-Asn (94%) and 51-Ile (91%) were very common. All infections with less than two DHFR/DHPS mutations were successfully treated. The prevalence of DHFR 59-Arg (57%), DHPS 437-Gly (58%) and 540-Glu (66%) was lower, with many samples showing a mixed wild-type and mutant profile. DHFR 59-Arg, DHPS 437-Gly and 540-Glu showed clinical significance mostly at day 28 {DHFR 59 (0.061 by day 14 and 0.003 by day 28), DHPS 437 (0.072 and 0.015) and 540 (0.031 and 0.0007) on days 14 and 28 respectively for each codon}. Combining them, 59-Arg + 540-Glu had the strongest association with clinical outcome at 28 days (p=0.002). To examine the theory that increasing resistance is associated with increasing number of mutations, there was a 50% risk of treatment failure in patients with 5 mutations than 0-4 mutations (p=0.0001).
The second study was designed to provide baseline information on the efficacy of SP and the prevalence of molecular markers that are associated with SP resistance in Kasangati. Blood samples were collected on Whatman’s filter paper from 169 consenting patients who were diagnosed with malaria. Patients were treated with SP and followed for 14 days. SP monotherapy was efficacious for 140 of 163 (85.9%) treated patients. We found a high level of mutations in alleles that have previously been reported to be associated with SP resistance, but there was no statisticall significant relationship between clinical outcomes and molecular markers (P. value 0.106). With the exception of codon S108 in DHFR (DHFR S108N was at 94.9%), frequencies of DHPS mutant and mixed alleles combined (A437G 89% and K540E 83.9%) were higher than those of DHFR (N51I 58.4%, C59R 31.3%).
The last two studies were done to evaluate the national anti-malarial policy drugs and assist evidence based national policy guidelines. We compared the clinical, parasitological and molecular findings of one study with treatment arms of CQSP, amodiaquine (AQ) plus SP (AQSP) done in 2003 with a study done 1 year earlier (2002) using SP alone
There was a notable decrease in adequate clinical response (ACR) by day 14 from 92.7% with SP to 80% with the combination CQSP, a year later. AQSP combination was found to have the best effect (ACR 94.3% compared to CQSP 80%, p. value 0.008). There were no early treatment failures in the AQSP group. Treatment failures were recorded at 20% on day 14 and 43% on day 28 for CQSP treatment and 5.7% by day 14 and 28.8% by day 28 in the AQSP group. The number of mutations that are associated with SP resistance increased from 2002 to 2003 at all loci monitored, from 83.8 to 100% at codon 108, 58.7 to 76% at codon 59 in the DHFR gene, and from 58.8 to 86% at codon 437 and 33 to 43% at codon 540 in the DHPS gene.
We conclude that there has been a rapid development of resistance since the introduction of new policy guidelines. AQSP was found to be a superior drug combination compared to CQSP and could be used as a low cost alternative to co-artem at the moment. | en_US |
