The efficacy of chloroquine for the treatment of acute, uncomplicated, Plasmodium falciparum malaria in Laos

Haematological consequences of acute uncomplicated falciparum malaria: a WorldWide Antimalarial Resistance Network pooled analysis of individual patient data

BACKGROUND

Plasmodium falciparum malaria is associated with anaemia-related morbidity, attributable to host, parasite and drug factors. We quantified the haematological response following treatment of uncomplicated P. falciparum malaria to identify the factors associated with malarial anaemia.

METHODS

Individual patient data from eligible antimalarial efficacy studies of uncomplicated P. falciparum malaria, available through the WorldWide Antimalarial Resistance Network data repository prior to August 2015, were pooled using standardised methodology. The haematological response over time was quantified using a multivariable linear mixed effects model with nonlinear terms for time, and the model was then used to estimate the mean haemoglobin at day of nadir and day 7. Multivariable logistic regression quantified risk factors for moderately severe anaemia (haemoglobin < 7 g/dL) at day 0, day 3 and day 7 as well as a fractional fall ≥ 25% at day 3 and day 7.

RESULTS

A total of 70,226 patients, recruited into 200 studies between 1991 and 2013, were included in the analysis: 50,859 (72.4%) enrolled in Africa, 18,451 (26.3%) in Asia and 916 (1.3%) in South America. The median haemoglobin concentration at presentation was 9.9 g/dL (range 5.0-19.7 g/dL) in Africa, 11.6 g/dL (range 5.0-20.0 g/dL) in Asia and 12.3 g/dL (range 6.9-17.9 g/dL) in South America. Moderately severe anaemia (Hb < 7g/dl) was present in 8.4% (4284/50,859) of patients from Africa, 3.3% (606/18,451) from Asia and 0.1% (1/916) from South America. The nadir haemoglobin occurred on day 2 post treatment with a mean fall from baseline of 0.57 g/dL in Africa and 1.13 g/dL in Asia. Independent risk factors for moderately severe anaemia on day 7, in both Africa and Asia, included moderately severe anaemia at baseline (adjusted odds ratio (AOR) = 16.10 and AOR = 23.00, respectively), young age (age < 1 compared to ≥ 12 years AOR = 12.81 and AOR = 6.79, respectively), high parasitaemia (AOR = 1.78 and AOR = 1.58, respectively) and delayed parasite clearance (AOR = 2.44 and AOR = 2.59, respectively). In Asia, patients treated with an artemisinin-based regimen were at significantly greater risk of moderately severe anaemia on day 7 compared to those treated with a non-artemisinin-based regimen (AOR = 2.06 [95%CI 1.39-3.05], p < 0.001).

CONCLUSIONS

In patients with uncomplicated P. falciparum malaria, the nadir haemoglobin occurs 2 days after starting treatment. Although artemisinin-based treatments increase the rate of parasite clearance, in Asia they are associated with a greater risk of anaemia during recovery.

Challenges and prospects for dengue and malaria control in Thailand, Southeast Asia

Despite significant advances in the search for potential dengue vaccines and new therapeutic schemes for malaria, the control of these diseases remains difficult. In Thailand, malaria incidence is falling whereas that of dengue is rising, with an increase in the proportion of reported severe cases. In the absence of antiviral therapeutic options for acute dengue, appropriate case management reduces mortality. However, the interruption of transmission still relies on vector control measures that are currently insufficient to curtail the cycle of epidemics. Drug resistance in malaria parasites is increasing, compromising malaria control and elimination. Deficiencies in our knowledge of vector biology and vectorial capacity also hinder public health efforts for vector control. Challenges to dengue and malaria control are discussed, and research priorities identified.

Efficacy of artemether-lumefantrine, the nationally-recommended artemisinin combination for the treatment of uncomplicated falciparum malaria, in southern Laos

Background

The Lao Government changed the national policy for uncomplicated Plasmodium falciparum malaria from chloroquine to artemether-lumefantrine (AL) in 2005. Since then, no information on AL efficacy has been reported. With evidence of resistance to artemisinin derivatives in adjacent Cambodia, there has been a concern as to AL efficacy. Monitoring of AL efficacy would help the Lao Government to make decisions on appropriate malaria treatment.

Methods

The efficacy of a three-day, twice daily oral artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in Xepon District, Savannakhet Province, southern Laos was studied over 42 days follow-up. This was part of a trial of thiamin supplementation in falciparum malaria.

Results

Of 630 patients with P. falciparum enrolled in the trial of thiamin treatment, 549 (87%, 357 children ≤15 years and 192 adults) were included in this study. The per protocol 42-day cure rates were 97% (524/541) [96% (337/352) for children and 99% (187/189) for adults, p = 0.042]. By conventional intention-to-treat analysis, the 42-day cure rates adjusted for re-infection, were 97% (532/549) [96% (342/357) in children and 99% (190/192) in adults, p = 0.042]. The proportion of patients who remained parasitaemic at day 1 after treatment was significantly higher in children [33% (116/356)] compared to adults [15% (28/192)] (p < 0.001) and only one adult patient had detectable parasitaemia on day 2. There were no serious adverse events. Potential side effects after treatment were reported more commonly in adults (32%) compared to children (15%) (p < 0.001). Patients with recrudescent infections were significantly younger, had longer mean time to fever clearance, and had longer median time to parasite clearance compared to those who were cured.

Conclusions

The current nationally-recommended anti-malarial treatment (artemether-lumefantrine) remains highly efficacious for the treatment of uncomplicated falciparum malaria five years after introduction in Laos. Regular monitoring is required in case artemisinin-resistant P. falciparum parasites should appear.

Trial registration

ISRCTN85411059.

An assessment of early diagnosis and treatment of malaria by village health volunteers in the Lao PDR

Background

Early diagnosis and treatment (EDAT) is crucial to reducing the burden of malaria in low-income countries. In the Lao PDR, this strategy was introduced in 2004-2005 and an assessment was performed at the community level in January 2007.

Methods

EDAT with malaria rapid diagnostic test (MRDT) and artemisinin combination therapy (ACT) was prospectively assessed among 36 randomized village health volunteers (VHVs) and 720 patients in six malaria-endemic provinces of Laos (three pilot provinces (PP), and three non-pilots provinces (NPP)). ACT was also retrospectively assessed among 2188 patients within the same areas from June to November 2006. Two checklists were used and scores were calculated.

Results

EDAT performance of the VHVs was rated better in PP than in NPP (16.67% versus 38.89%, respectively, p = 0.004). Nearly all VHVs could diagnose malaria but only 16 (44%) could describe the symptoms of severe malaria. In January 2007, 31/720 (4%) patients tested positive using the Paracheck^® test, 35 (5%) with microscopy (sensibility: 74.3%, specificity 99.3%, positive and negative predictive values: 83.9% and 98.7%, respectively). Patients from June to November were at higher risk of malaria: 35.19% of 2,188 febrile patients were positive (OR: 10.6, 95%CI: 7.4-15.5, p < 0.000). VHVs reported the MRDT easy to use, and yielded a satisfactory performance score. EDAT performance was rated as poor despite satisfactory results regarding ACT treatment, duration and dosages. Pre-referral treatment of severe malaria was infrequent and often inadequate, with 20% of these patients dying. Results suggest a higher mortality from severe malaria than officially reported. Shortage of ACT was frequent.

Discussion and conclusion

MRDT and ACT are useful and efficient and can be used by VHVs. VHVs' global EDAT performance is enhanced through training and monitoring. Persistent gaps in knowledge, care of patients and wrong treatment have to be addressed.

Monitoring Plasmodium falciparum chloroquine resistance in Yunnan Province, China, 1981-2006

The emergence and spread of drug resistant malaria parasites are an important factor contributing to the global resurgence of malaria, demonstrating the essence of drug resistance surveillance in endemic areas. In the malarious border regions of Yunnan Province, China, we have selected three study sites to monitor in vitro and in vivo resistance of Plasmodium falciparum parasites to chloroquine (CQ) from 1981 to 2006. In vitro studies using the microtest clearly showed high degree of CQ resistance in the early 1980s, when CQ was replaced by artemether monotherapy for falciparum malaria. In subsequent in vitro surveys performed in the early 1990s and 2003-2004, we found reductions in both the concentrations inhibiting 50% parasite growth (IC(50)s) and the percentage of resistant parasites at all study sites, although the degrees of the reduction varied among sites. Even though amodiaquine has never been used in this area, there were consistently high levels of resistance to this drug, confirming crossresistance between CQ and amodiaquine. In vivo clinical studies were consistent with the results of the in vitro assays. The overall rate of resistant clinical cases decreased from 97% in 1981-1983 to 40% in 2005-2006. Collectively, whereas a general trend of reduction in CQ resistance was observed in Yunnan, variations among sites existed in this relatively small area, probably as the result of both geographical heterogeneity of malaria epidemiology in Yunnan and different levels of CQ resistance in neighboring countries.

Assessing antimalarial efficacy in a time of change to artemisinin-based combination therapies: the role of Médecins Sans Frontières

Jean-Paul Guthmann and colleagues describe the output of MSF's work in antimalarial efficacy assessment during the last decade.

Diagnosis and management of malaria by rural community health providers in the Lao People's Democratic Republic (Laos)

We assessed the knowledge of malaria diagnosis and management by community health providers in rural Vientiane and Savannakhet Provinces, Lao PDR. Sixty health providers (17 pharmacy owners/drug sellers and 43 village health volunteers) were interviewed. All diagnosed malaria using symptoms and signs only; 14% were aware of >2 criteria for the diagnosis of severe malaria. Although chloroquine and quinine, the then recommended Lao national policy for uncomplicated malaria treatment, were the most common antimalarials prescribed - 65% gave incorrect doses and 70% did not know the side effects. Although not recommended by the then national policy, 27% of the health providers used combinations of antimalarials as they considered monotherapy ineffective. This study strongly suggests that further training of Lao rural health providers in malaria diagnosis and management is needed to improve the quality of health services in areas remote from district hospitals.

An open, randomized comparison of artesunate plus mefloquine vs. dihydroartemisinin–piperaquine for the treatment of uncomplicated Plasmodium falciparum malaria in the Lao People's Democratic Republic (Laos)

OBJECTIVE

To determine the efficacy and safety of oral dihydroartemisinin-piperaquine (DP, Artekin) in the treatment of uncomplicated Plasmodium falciparum malaria in southern Laos.

METHODS

An open, randomized clinical trial of oral artesunate-mefloquine (AM) vs. DP in 220 patients with acute uncomplicated falciparum malaria in Savannakhet Province, Laos.

RESULTS

The 42-day cure rates (95% CI), as determined by survival analysis and adjusted for reinfection, were excellent and similar for the two groups [99 (94-100)% and 100 (100-100)% for AM and DP, respectively]. The median (range) fever and parasite clearance times for the AM and DP groups were also similar [20 (4-63) h and 2 (1-4) days vs. 20 (7-57) and 2 (1-4) days, logrank P = 0.4 and 0.17, respectively]. There were more patients with at least one potential side effect following treatment in the AM group when compared with the DP group [64/110 (58%) vs. 48/110 (44%), respectively, P = 0.031].

CONCLUSION

Dihydroartemisinin-piperaquine did not have superior efficacy to AM for the treatment of uncomplicated falciparum malaria in Laos but was associated with fewer adverse effects.

Selection strength and hitchhiking around two anti-malarial resistance genes

Neutral mutations may hitchhike to high frequency when they are situated close to sites under positive selection, generating local reductions in genetic diversity. This process is thought to be an important determinant of levels of genomic variation in natural populations. The size of genome regions affected by genetic hitchhiking is expected to be dependent on the strength of selection, but there is little empirical data supporting this prediction. Here, we compare microsatellite variation around two drug resistance genes (chloroquine resistance transporter (pfcrt), chromosome 7, and dihydrofolate reductase (dhfr), chromosome 4) in malaria parasite populations exposed to strong (Thailand) or weak selection (Laos) by anti-malarial drugs. In each population, we examined the point mutations underlying resistance and length variation at 22 (chromosome 4) or 25 (chromosome 7) microsatellite markers across these chromosomes. All parasites from Thailand carried the K76T mutation in pfcrt conferring resistance to chloroquine (CQ) and 2-4 mutations in dhfr conferring resistance to pyrimethamine. By contrast, we found both wild-type and resistant alleles at both genes in Laos. There were dramatic differences in the extent of hitchhiking in the two countries. The size of genome regions affected was smaller in Laos than in Thailand. We observed significant reduction in variation relative to sensitive parasites for 34-64 kb (2-4 cM) in Laos on chromosome 4, compared with 98-137 kb (6-8 cM) in Thailand. Similarly, on chromosome 7, we observed reduced variation for 34-69 kb (2-4 cM) around pfcrt in Laos, but for 195-268 kb (11-16 cM) in Thailand. Reduction in genetic variation was also less extreme in Laos than in Thailand. Most loci were monomorphic in a 12 kb region surrounding both genes on resistant chromosomes from Thailand, whereas in Laos, even loci immediately proximal to selective sites showed some variation on resistant chromosomes. Finally, linkage disequilibrium (LD) decayed more rapidly around resistant pfcrt and dhfr alleles from Laos than from Thailand. These results demonstrate that different realizations of the same selective sweeps may vary considerably in size and shape, in a manner broadly consistent with selection history. From a practical perspective, genomic regions containing resistance genes may be most effectively located by genome-wide association in populations exposed to strong drug selection. However, the lower levels of LD surrounding resistance alleles in populations under weak selection may simplify identification of functional mutations.

Therapeutic efficacy of artemether-lumefantrine and artesunate-mefloquine for treatment of uncomplicated Plasmodium falciparum malaria in Luang Namtha Province, Lao People's Democratic Republic

The efficacy of the six-dose regimen of artemether-lumefantrine was compared with the combination of artesunate and mefloquine in a randomised, comparative trial in Luang Namtha Province, Northern Laos. Of 1033 screened patients, 201 were positive for Plasmodium falciparum; 108 patients of all age groups (2-66 years) with acute, uncomplicated P. falciparum malaria were enrolled in the study, 100 of whom were followed-up for 42 days. Fifty-three patients received artemether-lumefantrine and 55 received artesunante-mefloquine. Both drug combinations induced rapid clearance of parasites and malaria symptoms; there was no significant difference in the initial therapeutic response parameters. Both regimes were well tolerated. After 42 days, cure rates were 93.6% (95% CI = 82.5-98.7%; 44 of 47 patients) for artemether-lumefantrine and 100% (95% CI = 93.3-100.0%; 53 of 53 patients) for artesunate-mefloquine. The results show the excellent efficacy and tolerability of both artemether-lumefantrine and artesunate-mefloquine in Northern Laos.

In vivo assessment of drug efficacy against Plasmodium falciparum malaria: duration of follow-up

To determine the optimum duration of follow-up for the assessment of drug efficacy against Plasmodium falciparum malaria, 96 trial arms from randomized controlled trials (RCTs) with follow-up of 28 days or longer that were conducted between 1990 and 2003 were analyzed. These trials enrolled 13,772 patients, and participating patients comprised 23% of all patients enrolled in RCTs over the past 40 years; 61 (64%) trial arms were conducted in areas where the rate of malaria transmission was low, and 58 (50%) trial arms were supported by parasite genotyping to distinguish true recrudescences from reinfections. The median overall failure rate reported was 10% (range, 0 to 47%). The widely used day 14 assessment had a sensitivity of between 0 and 37% in identifying treatment failures and had no predictive value. Assessment at day 28 had a sensitivity of 66% overall (28 to 100% in individual trials) but could be used to predict the true failure rate if either parasite genotyping was performed (r(2) = 0.94) or if the entomological inoculation rate was known. In the assessment of drug efficacy against falciparum malaria, 28 days should be the minimum period of follow-up.

Randomized Comparison of Chloroquine plus Sulfadoxine-Pyrimethamine versus Artesunate plus Mefloquine versus Artemether-Lumefantrine in the Treatment of Uncomplicated Falciparum Malaria in the Lao People's Democratic Republic

BACKGROUND

Recent clinical trials in the Lao People's Democratic Republic have demonstrated that chloroquine and sulfadoxine-pyrimethamine, which are national malaria treatment policy, are no longer effective in the treatment of uncomplicated Plasmodium falciparum malaria.

METHODS

A randomized comparison of 3 oral antimalarial combinations--chloroquine plus sulfadoxine-pyrimethamine versus artesunate plus mefloquine versus artemether-lumefantrine--with 42-day follow-up period, was conducted among 330 patients with acute uncomplicated falciparum malaria in southern Laos.

RESULTS

The 42-day cure rates, as determined by intention-to-treat analysis and adjusted for reinfection, were 100%, 97%, and 93% for the groups receiving artesunate plus mefloquine, artemether-lumefantrine, and chloroquine plus sulfadoxine-pyrimethamine, respectively. Of 8 patients receiving chloroquine plus sulfadoxine-pyrimethamine who experienced treatment failure, 6 had early treatment failure. The mean parasite clearance time was significantly longer in patients treated with chloroquine plus sulfadoxine-pyrimethamine (2.9 days; 95% confidence interval [CI], 2.8-3.0 days) than in those treated with artesunate plus mefloquine (2.07 days; 95% CI, 2.0-2.1 days; P<.001) and artemether-lumefantrine (2.08 days; 95% CI, 2.0-2.1 days; P<.001). Cure rates with artemether-lumefantrine were high despite low mean daily dietary fat intake (13.8 g; 95% CI, 12.5-15.1 g) and day 7 plasma lumefantrine concentrations (0.47 mu g/mL; 95% CI, 0.38-0.56 mu g/mL).

CONCLUSION

Oral artesunate plus mefloquine and artemether-lumefantrine are highly effective for the treatment of uncomplicated falciparum malaria in Laos.

A randomized comparison of oral chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated Plasmodium falciparum malaria in Laos

Between June and October 2000 we conducted the first randomized trial in Laos comparing chloroquine (CQ) with sulfadoxine-pyrimethamine (SP) in the treatment of uncomplicated Plasmodium falciparum malaria (n = 29, 42-d follow-up, age > 5 years). The proportion of patients with treatment failure was high (CQ = 78%, RIII 46%; SP = 36%, RIII 15%). The treatment policy for uncomplicated P. falciparum malaria in Laos needs to be reviewed urgently.

Chloroquine versus sulfadoxine-pyrimethamine for treatment of Plasmodium falciparum malaria in Savannakhet Province, Lao People's Democratic Republic: an assessment of national antimalarial drug recommendations

The in vivo efficacies of the Lao People's Democratic Republic (Laos) nationally recommended antimalarial agents--chloroquine and sulfadoxine-pyrimethamine-were assessed in a randomized, comparative trial that involved 100 patients with uncomplicated Plasmodium falciparum malaria who were followed for 42 days after starting treatment. Despite a shorter mean time to fever clearance associated with administration of chloroquine (mean time to clearance, 35.6 h; 95% confidence interval [CI], 26.3-45.0 h), compared with that associated with sulfadoxine-pyrimethamine (61.1 h; 95% CI, 50.9-71.3 h; P<.001), treatment failures were twice as frequent among patients receiving chloroquine therapy than among those receiving sulfadoxine-pyrimethamine therapy (36% vs. 18%; P=.02). Of 23 treatment failures, 10 (43%) were high grade. Treatment failure rates among children (age range, 5-15 years) were 4.9 times higher (95% CI, 2-12) than those among adults (P<.0001). Gametocytemia after antimalarial treatment was associated with receipt of sulfadoxine-pyrimethamine therapy and with treatment failure (P=.009). The efficacy of both chloroquine and sulfadoxine-pyrimethamine in Laos is unsatisfactory.

Plasmodium falciparum: correlation of in vivo resistance to chloroquine and antifolates with genetic polymorphisms in isolates from the south of Lao PDR

Levels of drug resistance of Plasmodium falciparum strains against antimalarials have increased in Laos. In several studies, chloroquine (CQ) resistance has been associated with point mutations in the Pfcrt and pfmdr genes, and sulphadoxine/pyrimethamine (S/P) resistance with point mutations in the genes of dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). We combined a study of these molecular markers with an in vivo antimalarial drug sensitivity study in Attapeu province in the south of Lao PDR. We treated 100 patients with either CQ, S/P or a combination of both. In the CQ group, Pfcrt mutations showed a very high sensitivity (100%) but a low specificity (12.5%) to predict resistance. The combination of mutations in the Pfcrt and pfmdr genes was highly specific and had a positive predictive value of 100%. Mutations in the DHPS gene showed a high correlation with the development of resistance. The prevalence of mutations in the DHFR gene, especially codon 108 Asn, was predictive with high sensitivity (100%) but low specificity. Isolates derived from patients treated with a combination of both drugs showed a high correlation between the mutation in codon 437 of DHPS gene and in vivo-resistance (odds ratio 16.00, CI). The study provides evidence for the existence of antimalarial drug resistance in the south of Lao PDR, and offers a molecular method to predict resistance.