Antimalarial drug use in general populations of tropical Africa

Poly(N-vinylpyrrolidone) Antimalaria Conjugates of Membrane-Disruptive Peptides

The concepts of polymer-peptide conjugation and self-assembly were applied to antimicrobial peptides (AMPs) in the development of a targeted antimalaria drug delivery construct. This study describes the synthesis of α-acetal, ω-xanthate heterotelechelic poly(N-vinylpyrrolidone) (PVP) via reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization, followed by postpolymerization deprotection to yield α-aldehyde, ω-thiol heterotelechelic PVP. A specific targeting peptide, GSRSKGT, for Plasmodium falciparum-infected erythrocytes was used to sparsely decorate the α-chain ends via reductive amination while cyclic decapeptides from the tyrocidine group were conjugated to the ω-chain end via thiol-ene Michael addition. The resultant constructs were self-assembled into micellar nanoaggregates whose sizes and morphologies were determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The in vitro activity and selectivity of the conjugates were evaluated against intraerythrocytic P. falciparum parasites.

School-based social and behavior change communication (SBCC) advances community exposure to malaria messages, acceptance, and preventive practices in Ethiopia: A pre-posttest study

Background

Ethiopia has shown incredible success in malaria morbidity, mortality, and control. Community empowerment is a milestone to meet the ambitious plans of eliminating malaria by 2030.

Objectives

This study aimed to evaluate school-based malaria social behavior change communication (SBCC) in terms of community message exposure, acceptance, knowledge, and practices.

Methods

A community-based pre-posttest study was conducted in five districts of the Jimma Zone, Ethiopia. 762 and 759 households were sampled for baseline and end-line, respectively. The intervention engaged students from primary schools on participatory peer education within small groups, followed by exposing parents with malaria messages aimed to influencing ideation and preventive practices. The data were analyzed using Statistical Package for Social Sciences (SPSS) version 20.0. Proportion/mean differences were computed to compare both surveys on exposure, knowledge, perceptions, and practices at p <0.05. Finally, a regression analysis was conducted between key changes and school-based exposure.

Results

The study revealed a sharp increase in exposure to malaria messages with effect size (ES) of 65.7%, p <0.001. School specific exposure has grown to 57.8% (ES = 44.5%). Comprehensive knowledge about malaria increased to 39.1% (ES = 14.8%). Identifying mosquito bites as a cause of malaria was increased by ES = 20.8%. A slight reduction in risk perception (ES = 3.3%) and attitude (ES = 3.8%) and a higher rise in self-efficacy (ES = 8.5%) were observed. Community message acceptance in favor of malaria danger control was significantly improved by 10% i.e. an increase in rational decision making to uptake preventive practices. Consistently, insecticide-treated nets (ITNs) usage was improved to 63.0% (ES = 25.8%). Giving priority to use ITNs for under five years old children and pregnant women grew by 16.3% and 24.8%, respectively. Significant improvements were observed in treatment-seeking for fever (ES = 16.3%) and early treatment-seeking (ES = 15.5%). Not painting or plastering walls 6 months within spraying changed by ES = 61%. No significant change was observed in drug adherence. The school-based content intensity of exposure had effects on comprehensive knowledge, message acceptance, and ITN utilization.

Conclusions

Engaging school-aged children effectively advances community exposure, perception, and behaviors. We recommend the inclusion of school-based SBCC in the national malaria control programs.

Predictors of residual antimalarial drugs in the blood in community surveys in Tanzania

Background

Understanding pattern of antimalarials use at large scale helps ensuring appropriate use of treatments and preventing the spread of resistant parasites. We estimated the proportion of individuals in community surveys with residual antimalarials in their blood and identified the factors associated with the presence of the most commonly detected drugs, lumefantrine and/or desbutyl-lumefantrine (LF/DLF) or sulfadoxine-pyrimethamine (SP).

Methods

A cross-sectional survey was conducted in 2015 in three regions of Tanzania with different levels of malaria endemicity. Interviews were conducted and blood samples collected through household surveys for further antimalarial measurements using liquid chromatography coupled to tandem mass spectrometry. In addition, diagnosis and treatment availability was investigated through outlet surveys. Multilevel mixed effects logistic regression models were used to estimate odds ratios for having LF/DLF or SP in the blood.

Results

Amongst 6391 participants, 12.4% (792/6391) had LF/DLF and 8.0% (510/6391) SP in the blood. Factors associated with higher odds of detecting LF/DLF in the blood included fever in the previous two weeks (OR = 2.6, p<0.001), living in districts of higher malaria prevalence (OR = 1.5, p<0.001) and living in a ward in which all visited drug stores had artemisinin-based combination therapies in stocks (OR = 2.7, p = 0.020). Participants in older age groups were less likely to have LF/DLF in the blood (OR = 0.9, p<0.001). Factors associated with higher odds of having SP in the blood included being pregnant (OR = 4.6, p<0.001), living in Mwanza (OR = 3.9, p<0.001 compared to Mbeya), fever in the previous two weeks (OR = 1.7, p<0.001) and belonging to older age groups (OR = 1.2, p<0.001).

Conclusion

The most significant predictors identified were expected. History of fever in the past two weeks and young age were significant predictors of LF/DLF in the blood, which is encouraging. Antimalarial drug pressure was high and hence the use of recommended first-line drugs in combination with malaria Rapid Diagnostics Tests should be promoted to ensure appropriate treatment.

Drug use in the management of uncomplicated malaria in public health facilities in the Democratic Republic of the Congo

Background

Malaria the first causes of death from parasitic infection worldwide. Interventions to reduce the burden of malaria have produced a tremendous drop in malaria morbidity and mortality. However, progress is slower in DRC, which shares with Nigeria 39% of deaths related to malaria globally. Inappropriate use of drugs may be one of the factors of this below-average performance. The aim of this study was to describe the use of drugs in the management of uncomplicated malaria in public health facilities in DRC.

Methods

A drug use study was carried out in DRC from January to March 2014. In each of the former 11 provinces of DRC, one Rural Health Centre, one Urban Health Centre and one General Hospital were selected. In each of them, 100 patient’s files containing prescription of anti-malarials from January to December 2013 were randomly selected. Among them, all of the files with diagnosis of uncomplicated malaria were included in this study. Prescribed anti-malarials, co-prescribed drugs and their indications were collected. Descriptive analyses were performed.

Results

A total of 2300 files out of 3300 (69.7%) concerned uncomplicated malaria and were included in analysis. Malaria treatment was initiated after a positive RDT or microscopy in 51.5% of cases, upon suspicion without requesting biological confirmation in 37% and despite negative results in 11%. Twenty-nine (29) different treatment regimens were used. The drugs recommended by the National Malaria Control Programme were used in 54.3% of cases (artesunate–amodiaquine 37.4% or artemether–lumefantrine 16.9%). The second most used anti-malarial was quinine (32.4%). Apart from anti-malarials, an average of 3.1 drugs per patient were prescribed, among which antibiotics (67.9%), analgesics and non-steroidal anti-inflammatory (NSAIDs) (all abbreviations to be explicated on first use) (70.6%), vitamins (29.1%), anaemia drugs, including blood transfusion (9.1%) and corticosteroids (5.7%), In 51.4% of cases there was no indication for the concomitant medication.

Conclusion

Management of uncomplicated malaria in DRC is characterized by a low adherence to treatment policy, numerous treatment regimens, and abundant concomitant medication potentially harmful to the patient. This may contribute to the low performance of DRC in malaria control. Determinant of this irrational use of drugs need to be assessed in order to formulate and implement efficient corrective measures.

Biological and Phytochemical Investigations on Caesalpinia benthamiana, a Plant Traditionally Used as Antimalarial in Guinea

Caesalpinia benthamiana is widely used as antimalarial in Guinean traditional medicine. Leaf extracts of the plant were tested for their in vitro antiprotozoal activity against Trypanosoma brucei brucei and T. cruzi and the chloroquine-sensitive Ghana strain of Plasmodium falciparum along with their cytotoxicity on MRC-5 cells. The methanolic extract showed the strongest antiprotozoal activity against P. falciparum (IC₅₀ 4 μg/ml), a good activity against T. brucei (IC₅₀ 13 μg/ml), and a moderate activity against T. cruzi (IC₅₀ 31 μg/ml) along with an IC₅₀ on human MRC-5 cells of 32 μg/ml. Bioassay-guided fractionation from the methanolic extract led to antiplasmodially active subfractions. A prospective, placebo-controlled ethnotherapeutic trial assessed the antimalarial effectiveness and tolerability of C. benthamiana syrup administered orally to children with uncomplicated malaria as compared with chloroquine syrup. Phytochemical screening of the leaf extracts indicated the presence of flavonoids, terpenoids, tannins, saponins, and iridoids.

Progressive increase in point mutations associates chloroquine resistance: Even after withdrawal of chloroquine use in India

Chloroquine (CQ) is highly effective against P. vivax, due to the rapid spread of CQ resistance in P. falciparum parasites; it is no longer the drug of choice against P. falciparum. This study elucidates the scenario of chloroquine efficacy at times that coincided with a new drug policy and especially assessed the chloroquine resistant molecular markers after withdrawal of chloroquine in Kolkata and Purulia, two malaria endemic zones of West Bengal, India. In vitro CQ susceptibility was tested in 781 patients with P. falciparum mono infections between 2008 and 2013, of which 338 patients had received CQ in 2008–2009. Genotyping of the pfcrt and the pfmdr1 gene was carried out in all isolates. Early treatment failure was detected in 114 patients {43 (31·39%) from Kolkata and 71 (35·32%) from Purulia} while recrudescence was identified in 13 (9.49%) and 17 (8.46%) patients from Kolkata and Purulia respectively. In vivo chloroquine resistance was strongly associated with CVMNT-YYSNY (p < 0.01) and SVMNT-YYSNY (p < 0.05) allele in Kolkata. In Purulia chloroquine resistance was associated with CVMNK-YYSNY (P < 0.005), SVMNT-YYSNY (P < 0.01) allele. The proportion of in vitro chloroquine resistance increased in subsequent years to 87.23% and 93·10% in 2013, in Kolkata and Purulia, respectively. Isolates with SVMNT-YFSND, SVMNT-YFSNY, CVIET-YFSND and CVIET-YYSNY haplotypes increased gradually (p < 0.05) from 2010 to 2013, leading to a rise in IC₅₀ (p < 0.05) of chloroquine. An increase in in vitro chloroquine resistance and candidate gene mutations even after five years of chloroquine withdrawal against P. falciparum calls for synchronized research surveillance and proper containment strategies.

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Unremitting increase in pfcrt and pfmdr1 polymorphism without CQ drug pressure.

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In vitro CQ resistance was still increase after 5 years of ACT implementation.

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Regional bias in pfcrt and pfmdr1 polymorphism associates CQ resistance.

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Irresponsive self medication (CQ) by civilians made the situation worse day by day.

Malaria treatment using novel nano-based drug delivery systems

We reside in an era of technological innovation and advancement despite which infectious diseases like malaria remain to be one of the greatest threats to the humans. Mortality rate caused by malaria disease is a huge concern in the twenty-first century. Multiple drug resistance and nonspecific drug targeting of the most widely used drugs are the main reasons/drawbacks behind the failure in malarial therapy. Dose-related toxicity because of high doses is also a major concern. Therefore, to overcome these problems nano-based drug delivery systems are being developed to facilitate site-specific or target-based drug delivery and hence minimizing the development of resistance progress and dose-dependent toxicity issues. In this review, we discuss about the shortcomings in treating malaria and how nano-based drug delivery systems can help in curtailing the infectious disease malaria.

Chitosan/Sterculia striata polysaccharides nanocomplex as a potential chloroquine drug release device

Nanoparticles are produced by means of polyelectrolyte complexation (PEC) of oppositely charged polycationic chitosan (CH) with polyanionic polysaccharide extracted from Sterculia striata exudates (rhamnogalacturonoglycan (RG)-type polysaccharide). The nanoparticles formed with low-molar-mass CH are larger than those formed with high-molar-mass CH. This behavior is in contrast with that previously observed for other systems and may be attributed to different mechanisms related to the association of CH with RG of higher persistence length chain than that of CH. Nanoparticles harnessed with a charge ratio (n(+)/n(-)) of <1 are smaller than particles with an excess of polycations. Particles with hydrodynamic sizes smaller than 100nm are achieved using a polyelectrolyte concentration of 10(-4)gmL(-1) and charge ratio (n(+)/n(-)) of <1. The CH/RG nanoparticles are associated with chloroquine (CQ) with an efficiency of 28% and release it for up to ∼60% within ∼10h, whereas in the latter, only ∼40% of the CQ was released after 24h. The main factor that influenced drug release rate is the nanoparticle charge ratio.

A theoretical examination of the relative importance of evolution management and drug development for managing resistance

Drug resistance is a serious public health problem that threatens to thwart our ability to treat many infectious diseases. Repeatedly, the introduction of new drugs has been followed by the evolution of resistance. In principle, there are two complementary ways to address this problem: (i) enhancing drug development and (ii) slowing the evolution of drug resistance through evolutionary management. Although these two strategies are not mutually exclusive, it is nevertheless worthwhile considering whether one might be inherently more effective than the other. We present a simple mathematical model that explores how interventions aimed at these two approaches affect the availability of effective drugs. Our results identify an interesting feature of evolution management that, all else equal, tends to make it more effective than enhancing drug development. Thus, although enhancing drug development will necessarily be a central part of addressing the problem of resistance, our results lend support to the idea that evolution management is probably a very significant component of the solution as well.

Relationship between child survival and malaria transmission: an analysis of the malaria transmission intensity and mortality burden across Africa (MTIMBA) project data in Rufiji demographic surveillance system, Tanzania

BACKGROUND

The precise nature of the relationship between malaria mortality and levels of transmission is unclear. Due to methodological limitations, earlier efforts to assess the linkage have lead to inconclusive results. The malaria transmission intensity and mortality burden across Africa (MTIMBA) project initiated by the INDEPTH Network collected longitudinally entomological data within a number of sites in sub-Saharan Africa to study this relationship. This work linked the MTIMBA entomology database with the routinely collected vital events within the Rufiji Demographic Surveillance System to analyse the transmission-mortality relation in the region.

METHODS

Bayesian Bernoulli spatio-temporal Cox proportional hazards models with village clustering, adjusted for age and insecticide-treated nets (ITNs), were fitted to assess the relation between mortality and malaria transmission measured by entomology inoculation rate (EIR). EIR was predicted at household locations using transmission models and it was incorporated in the model as a covariate with measure of uncertainty. Effects of covariates estimated by the model are reported as hazard ratios (HR) with 95% Bayesian confidence interval (BCI) and spatial and temporal parameters are presented.

RESULTS

Separate analysis was carried out for neonates, infants and children 1-4 years of age. No significant relation between all-cause mortality and intensity of malaria transmission was indicated at any age in childhood. However, a strong age effect was shown. Comparing effects of ITN and EIR on mortality at different age categories, a decrease in protective efficacy of ITN was observed (i.e. neonates: HR = 0.65; 95% BCI:0.39-1.05; infants: HR = 0.72; 95% BCI:0.48-1.07; children 1-4 years: HR = 0.88; 95% BCI:0.62-1.23) and reduction on the effect of malaria transmission exposure was detected (i.e. neonates: HR = 1.15; 95% BCI:0.95-1.36; infants: HR = 1.13; 95% BCI:0.98-1.25; children 1-4 years: HR = 1.04; 95% BCI:0.89-1.18). A very strong spatial correlation was also observed.

CONCLUSION

These results imply that assessing the malaria transmission-mortality relation involves more than the knowledge on the performance of interventions and control measures. This relation depends on the levels of malaria endemicity and transmission intensity, which varies significantly between different settings. Thus, sub-regions analyses are necessary to validate and assess reproducibility of findings.

Ethnobotanical survey on medicinal plants used by Guinean traditional healers in the treatment of malaria

ETHNOPHARMACOLOGICAL RELEVANCE

The objective of the present study was to collect and document information on herbal remedies traditionally used for the treatment of malaria in Guinea.

MATERIALS AND METHODS

The survey was carried out from May 2008 to September 2010 and targeted traditional medical practitioners and herbalists. The questionnaire and oral interviews were based on the standardized model which was prepared by the "Centre de Recherche et de Valorisation des Plantes Médicinales (CRVPM) - Dubréka".

RESULTS AND DISCUSSION

A total of 258 people (141 males and 117 females) from which 150 traditional healers and 108 herbalists were interviewed. The age of informants ranged from 28 to 82 years old. 57% (149/258) of the interviewees were more than 50 years old. The respondents had good knowledge of the symptoms of malaria, and a fairly good understanding of the causes. One hundred thirteen plant species were recorded, out of which 109 were identified. They belonged to 84 genera and 46 families. The most frequently cited plants were Vismia guineensis, Parkia biglobosa, Nauclea latifolia, Harungana madagascariensis, Terminalia macroptera, Crossopteryx febrifuga, Terminalia albida, Annona senegalensis, and Nauclea pobeguinii. The leaves were most frequently used (80/113 species), followed by stem bark (38/113 species) and roots (4/113 species). The remedies were mostly prepared by decoction (111 species), followed by maceration (seven species). Only one species was prepared by infusion.

CONCLUSION

The present study showed that traditional healers in Guinea have a consistent knowledge of antimalarial plants. Further research should be carried out to compare the anti-malarial activity of the different species, and to check if their use against malaria can be scientifically validated.

Plasmodium falciparum susceptibility to anti-malarial drugs in Dakar, Senegal, in 2010: an ex vivo and drug resistance molecular markers study

Background

In 2006, the Senegalese National Malaria Control Programme recommended artemisinin-based combination therapy (ACT) as the first-line treatment for uncomplicated malaria. Since the introduction of ACT, there have been very few reports on the level of resistance of P. falciparum to anti-malarial drugs. To determine whether parasite susceptibility has been affected by the new anti-malarial policies, an ex vivo susceptibility and drug resistance molecular marker study was conducted on local isolates obtained from the Centre de santé Elizabeth Diouf (Médina, Dakar, Senegal).

Methods

The prevalence of genetic polymorphisms in genes associated with anti-malarial drug resistance, i.e., pfcrt, pfdhfr, pfdhps and pfmdr1, were evaluated for a panel of 165 isolates collected from patients recruited from 17 August 2010 to 6 January 2011. The malaria isolates were assessed for susceptibility to chloroquine (CQ); quinine (QN); monodesethylamodiaquine (MDAQ), the active metabolite of amodiaquine; mefloquine (MQ); lumefantrine (LMF); dihydroartemisinin (DHA), the active metabolite of artemisinin derivatives; and doxycycline (DOX) using the Plasmodium lactate dehydrogenase (pLDH) ELISA.

Results

The prevalence of the in vitro resistant isolates, or isolates with reduced susceptibility, was 62.1% for MQ, 24.2% for CQ, 10.3% for DOX, 11.8% MDAQ, 9.7% for QN, 2.9% for LMF and 0% for DHA. The Pfcrt 76T mutation was identified in 43.6% of the samples. The pfmdr1 86Y, 184F and 1246Y mutations were found in 16.2%, 50.0% and 1.6% of the samples, respectively. The pfdhfr 108N, 51I and 59R mutations were identified in 81.9%, 77.4% and 79.4% of the samples, respectively. The double mutant (108N and 51I) was detected in 75.5% of the isolates, and the triple mutant (108N, 51I and 59R) was detected in 73.6% of the isolates. The pfdhps 437G, 436A and 613S mutations were found in 54.4%, 38.6% and 1.2% of the samples, respectively. There was only one double mutant, 437G and 540E, and one quintuple mutant, pfdhfr 108N, 51I and 59R and pfdhps 437G and 540E. The prevalence of the quadruple mutant (pfdhfr 108N, 51I and 59R and pfdhps 437G) was 36.7%.

Conclusions

The results of this study indicate that an intensive surveillance of the in vitro P. falciparum susceptibility to anti-malarial drugs must be conducted in Senegal.

Association between prevalence of chloroquine resistance and unusual mutation in pfmdr-I and pfcrt genes in India

This study deals with the underlying causes of failure of chloroquine in the treatment of Plasmodium falciparum infection in some malaria-endemic regions of India. Samples were collected from 141 patients in Purulia from March of 2007 to April of 2008. In vitro drug susceptibility tests, parasitic DNA isolation followed by polymerase chain reaction, and restriction fragment-length polymorphisms of different codons of the pfcrt gene (76) and pfmdr-I genes (86, 1042, and 1246) were assessed. The responses of 141 patients to chloroquine were determined. Prevalence of double pfmdr-I (58.16%) mutation (86Y+1246Y) and some (14.89%) single pfcrt mutations with triple pfmdr-I mutation (76T+86Y+1042D+1246Y) were found. Interestingly, double pfmdr-I mutation (86Y and 1246Y codons) was observed with the early treatment failure cases. These results show, for the first time in India that in vitro chloroquine resistance and in vivo chloroquine treatment failure were caused by double pfmdr-I (P < 0.001) mutation.

Longitudinal study assessing the return of chloroquine susceptibility of Plasmodium falciparum in isolates from travellers returning from West and Central Africa, 2000-2011

Background

Chloroquine (CQ) was the main malaria therapy worldwide from the 1940s until the 1990s. Following the emergence of CQ-resistant Plasmodium falciparum, most African countries discontinued the use of CQ, and now promote artemisinin-based combination therapy as the first-line treatment. This change was generally initiated during the last decade in West and Central Africa. The aim of this study is to describe the changes in CQ susceptibility in this African region, using travellers returning from this region as a sentinel system.

Methods

The study was conducted by the Malaria National Reference Centre, France. The database collated the pfcrtK76T molecular marker for CQ susceptibility and the in vitro response to CQ of parasites from travellers’ isolates returning from Senegal, Mali, Ivory Coast or Cameroon. As a proxy of drug pressure, data regarding CQ intake in febrile children were collated for the study period. Logistic regression models were used to detect trends in the proportions of CQ resistant isolates.

Results

A total of 2874 parasite isolates were genotyped between 2000–2011. The prevalence of the pfcrt76T mutant genotype significantly decreased for Senegal (from 78% to 47%), Ivory Coast (from 63% to 37%), Cameroon (from 90% to 59%) and remained stable for Mali. The geometric mean of the 50% inhibitory concentration (IC₅₀) of CQ in vitro susceptibility and the proportion of resistant isolates (defining resistance as an IC50 value > 100 nM) significantly decreased for Senegal (from 86 nM (59%) to 39 nM (25%)), Mali (from 84 nM (50%) to 51 nM (31%)), Ivory Coast (from 75 nM (59%) to 29 nM (16%)) and Cameroon (from 181 nM (75%) to 51 nM (37%)). Both analyses (molecular and in vitro susceptibility) were performed for the 2004–2011 period, after the four countries had officially discontinued CQ and showed an accelerated decline of the resistant isolates for the four countries. Meanwhile, CQ use among children significantly deceased in this region (fixed effects slope = −0.3, p < 10^-3).

Conclusions

An increase in CQ susceptibility following official withdrawal of the drug was observed in travellers returning from West and Central African countries. The same trends were observed for molecular and in vitro analysis between 2004-2011and they correlated to the decrease of the drug pressure.

Mitigating the threat of artemisinin resistance in Africa: improvement of drug-resistance surveillance and response systems

Artemisinin-resistant Plasmodium falciparum malaria has emerged in western Cambodia and has been detected in western Thailand. The situation is ominously reminiscent of the emergence of resistance to chloroquine and to sulfadoxine-pyrimethamine several decades ago. Artemisinin resistance is a major threat to global public health, with the most severe potential effects in sub-Saharan Africa, where the disease burden is highest and systems for monitoring and containment of resistance are inadequate. The mechanisms that underlie artemisinin resistance are not fully understood. The main phenotypic trait associated with resistance is a substantial delay in parasite clearance, so far reported in southeast Asia but not in Africa. One of the pillars of the WHO global plan for artemisinin resistance containment is to increase monitoring and surveillance. In this Personal View, we propose strategies that should be adopted by malaria-endemic countries in Africa: resource mobilisation to reactivate regional surveillance networks, establishment of baseline parasite clearance profiles to serve as benchmarks to track emerging artemisinin resistance, improved data sharing to allow pooled analyses to identify rare events, modelling of risk factors for drug resistance, and development and validation of new approaches to monitor resistance.

Molecular analysis of markers associated with chloroquine and sulfadoxine/pyrimethamine resistance in Plasmodium falciparum malaria parasites from southeastern Côte-d'Ivoire by the time of Artemisinin-based Combination Therapy adoption in 2005

PURPOSE

Artemisin-based combination therapies became the recommended therapy in Côte-d'Ivoire in 2005, but both chloroquine (CQ) and sulfadoxine/pyrimethamine (SP) have been heavily used for many decades. Despite this long history, little is known about the geographical distribution of drug resistance-conferring genotypes outside the capital city of Abidjan. In this work, we compared the prevalence of drug-resistant genotypes in Bonoua, an urban area, and Samo, a rural agricultural area, in southeastern Côte-d'Ivoire, about 59 km from Abidjan.

PATIENTS AND METHODS

Samples were collected from symptomatic patients in both sites during the rainy season in 2005. Genomic DNA was isolated and codons associated with resistance to CQ and SP were analyzed: pfcrt codons Cys-72-Ser, Val-73-Val, Met-74-Ile, Arg-75-Glu, Lys-76-Thr; pfdhfr codons Ala-16-Val, Arg-51-Ile, Cys-59-Arg, Ser-108-Arg/Thr, and Ile-164-Leu; pfdhps codons Ser-436-Ala, Ala-437-Gly, Lys-540-Glu, Ala-581-Gly, and Ala-613-Thr/Ser.

RESULTS

A limited number of genotypes were found in Bonoua compared with Samo. In both sites, the triple-mutant allele CVIET of pfcrt predominated: 100% in Bonoua and 86.2% in Samo. The wild-type allele, NCSI of pfdhfr, was common - 50% in Bonoua and 38.7% in Samo - but the triple-mutant IRNI and double-mutant NRNI were also frequent (IRNI, 32.6% in Bonoua and 19.4% in Samo; NRNI, 15.2% in Bonoua and 9.7% in Samo). In Samo, a wide range of different genotypes of Pfdhps was observed, with alleles carrying the Gly-437 codon fixed in Bonoua and comprising 73% of the isolates in Samo.

CONCLUSION

Although these two sites are only 8 km apart, they belonged to very different ecological environments. The overall prevalence of alleles of single-nucleotide polymorphisms associated with resistance to CQ and SP in both locations was among the highest of the region by 2005, although the more rural site showed a more diverse set of alleles and mixed infections. Continued surveillance of these markers will be a useful tool for drug policy, as both CQ and SP are still frequently used years after withdrawal, and SP is recommended by the World Health Organization for intermittent preventive therapy for pregnant women and infants. Data analyzed herein are among the first to be generated during the year of artemisin-based combination-therapy introduction in Côte-d'Ivoire and could be of some interest for malaria policy-makers.

Prevalence of molecular markers of Plasmodium falciparum drug resistance in Dakar, Senegal

Background

As a result of the widespread resistance to chloroquine and sulphadoxine-pyrimethamine, artemisinin-based combination therapy (ACT) (including artemether-lumefantrine and artesunate-amodiaquine) has been recommended as a first-line anti-malarial regimen in Senegal since 2006. Intermittent preventive treatments with anti-malarial drugs based on sulphadoxine-pyrimethamine are also given to children or pregnant women once per month during the transmission season. Since 2006, there have been very few reports on the susceptibility of Plasmodium falciparum to anti-malarial drugs. To estimate the prevalence of resistance to several anti-malarial drugs since the introduction of the widespread use of ACT, the presence of molecular markers associated with resistance to chloroquine and sulphadoxine-pyrimethamine was assessed in local isolates at the military hospital of Dakar.

Methods

The prevalence of genetic polymorphisms in genes associated with anti-malarial drug resistance, i.e., Pfcrt, Pfdhfr, Pfdhps and Pfmdr1, and the copy number of Pfmdr1 were evaluated for a panel of 174 isolates collected from patients recruited at the military hospital of Dakar from 14 October 2009 to 19 January 2010.

Results

The Pfcrt 76T mutation was identified in 37.2% of the samples. The Pfmdr1 86Y and 184F mutations were found in 16.6% and 67.6% of the tested samples, respectively. Twenty-eight of the 29 isolates with the 86Y mutation were also mutated at codon 184. Only one isolate (0.6%) had two copies of Pfmdr1. The Pfdhfr 108N/T, 51I and 59R mutations were identified in 82.4%, 83.5% and 74.1% of the samples, respectively. The double mutant (108N and 51I) was detected in 83.5% of the isolates, and the triple mutant (108N, 51I and 59R) was detected in 75.3%. The Pfdhps 437G, 436F/A and 613S mutations were found in 40.2%, 35.1% and 1.8% of the samples, respectively. There was no double mutant (437G and 540E) or no quintuple mutant (Pfdhfr 108N, 51I and 59R and Pfdhps 437G and 540E). The prevalence of the quadruple mutant (Pfdhfr 108N, 51I and 59R and Pfdhps 437G) was 36.5%.

Conclusions

Since 2004, the prevalence of chloroquine resistance had decreased. The prevalence of isolates with high-level pyrimethamine resistance is 83.5%. The prevalence of isolates resistant to sulphadoxine is 40.2%. However, no quintuple mutant (Pfdhfr 108N, 51I and 59R and Pfdhps 437G and 540E), which is associated with a high level of sulphadoxine-pyrimethamine resistance, has been identified to date. The resistance to amodiaquine remains moderate.

Ex vivo susceptibility of Plasmodium falciparum isolates from Dakar, Senegal, to seven standard anti-malarial drugs

Background

As a result of widespread chloroquine and sulphadoxine-pyrimethamine resistance, artemisinin-based combination therapy (ACT) (which includes artemether-lumefantrine and artesunate-amodiaquine) has been recommended as a first-line anti-malarial regimen in Senegal since 2006. Since then, there have been very few reports on the ex vivo susceptibility of Plasmodium falciparum to anti-malarial drugs. To examine whether parasite susceptibility has been affected by the widespread use of ACT, the ex vivo susceptibility of local isolates was assessed at the military hospital of Dakar.

Methods

The ex vivo susceptibility of 93 P. falciparum isolates from Dakar was successfully determined using the Plasmodium lactate dehydrogenase (pLDH) ELISA for the following drugs: chloroquine (CQ), quinine (QN), mefloquine (MQ), monodesethylamodiaquine (MDAQ), lumefantrine (LMF), dihydroartemisinin (DHA) and doxycycline (DOX).

Results

After transformation of the isolate IC₅₀ in ratio of IC₅₀ according to the susceptibility of the 3D7 reference strain (isolate IC₅₀/3D7 IC₅₀), the prevalence of the in vitro resistant isolates with reduced susceptibility was 50% for MQ, 22% for CQ, 12% for DOX, 6% for both QN and MDAQ and 1% for the drugs LMF and DHA. The highest significant positive correlations were shown between responses to CQ and MDAQ (r = 0.569; P < 0.0001), LMF and QN (r = 0.511; P < 0.0001), LMF and DHA (r = 0.428; P = 0.0001), LMF and MQ (r = 0.413; P = 0.0002), QN and DHA (r = 0.402; P = 0.0003) and QN and MQ (r = 0.421; P = 0.0001).

Conclusions

The introduction of ACT in 2002 has not induced a decrease in P. falciparum susceptibility to the drugs DHA, MDAQ and LMF, which are common ACT components. However, the prevalence of P. falciparum isolates with reduced susceptibility has increased for both MQ and DOX. Taken together, these data suggest that intensive surveillance of the P. falciparum in vitro susceptibility to anti-malarial drugs in Senegal is required.

Bioorganometallic Chemistry and Malaria

This chapter summarizes recent developments in the design, synthesis, and structure–activity relationship studies of organometallic antimalarials. It begins with a general introduction to malaria and the biology of the parasite Plasmodium falciparum, with a focus on the heme detoxification system. Then, a number of metal complexes from the literature are reported for their antiplasmodial activity. The second half of the chapter deals with the serendipitous discovery of ferroquine, its mechanism(s) of action, and the failure to induce a resistance. Last, but not least, we suggest that the bioorganometallic approach offers the potential for the design of novel therapeutic agents.

Identification of a mutant PfCRT-mediated chloroquine tolerance phenotype in Plasmodium falciparum

Mutant forms of the Plasmodium falciparum transporter PfCRT constitute the key determinant of parasite resistance to chloroquine (CQ), the former first-line antimalarial, and are ubiquitous to infections that fail CQ treatment. However, treatment can often be successful in individuals harboring mutant pfcrt alleles, raising questions about the role of host immunity or pharmacokinetics vs. the parasite genetic background in contributing to treatment outcomes. To examine whether the parasite genetic background dictates the degree of mutant pfcrt-mediated CQ resistance, we replaced the wild type pfcrt allele in three CQ-sensitive strains with mutant pfcrt of the 7G8 allelic type prevalent in South America, the Oceanic region and India. Recombinant clones exhibited strain-dependent CQ responses that ranged from high-level resistance to an incremental shift that did not meet CQ resistance criteria. Nonetheless, even in the most susceptible clones, 7G8 mutant pfcrt enabled parasites to tolerate CQ pressure and recrudesce in vitro after treatment with high concentrations of CQ. 7G8 mutant pfcrt was found to significantly impact parasite responses to other antimalarials used in artemisinin-based combination therapies, in a strain-dependent manner. We also report clinical isolates from French Guiana that harbor mutant pfcrt, identical or related to the 7G8 haplotype, and manifest a CQ tolerance phenotype. One isolate, H209, harbored a novel PfCRT C350R mutation and demonstrated reduced quinine and artemisinin susceptibility. Our data: 1) suggest that high-level CQR is a complex biological process dependent on the presence of mutant pfcrt; 2) implicate a role for variant pfcrt alleles in modulating parasite susceptibility to other clinically important antimalarials; and 3) uncover the existence of a phenotype of CQ tolerance in some strains harboring mutant pfcrt.

Plasmodium falciparum resistance to the antimalarial drug chloroquine has been found to result primarily from point mutations in PfCRT, which provide a highly sensitive marker of in vivo treatment failure and in vitro resistance. Debate has nonetheless continued about the singular role of mutant PfCRT and the contribution of the parasite genetic background. To address this, we have generated recombinant P. falciparum lines expressing a mutant pfcrt allele, or the reference wild type allele, in three distinct chloroquine-sensitive strains. Their analysis reveals a spectrum of responses ranging from high-level resistance to a previously unrecognized tolerance phenotype. The latter is characterized by virtually unchanged chloroquine IC₅₀ values, significantly elevated IC₉₀ values, and the ability to recrudesce after exposure to drug concentrations that are lethal to chloroquine-sensitive parasites. This tolerance phenotype was also observed in an isolate from French Guiana, confirming its presence in malaria-endemic regions. Mutant PfCRT significantly affected parasite responses to other antimalarials, including ones used in artemisinin-based combination therapies, in a strain-dependent manner. Our data suggest that successful CQ treatment of drug-resistant parasites is dependent on both host immunity and the strain-dependent extent to which mutant pfcrt imparts resistance.

Nanotechnology applied to the treatment of malaria

Despite the fact that we live in an era of advanced technology and innovation, infectious diseases, like malaria, continue to be one of the greatest health challenges worldwide. The main drawbacks of conventional malaria chemotherapy are the development of multiple drug resistance and the non-specific targeting to intracellular parasites, resulting in high dose requirements and subsequent intolerable toxicity. Nanosized carriers have been receiving special attention with the aim of minimizing the side effects of drug therapy, such as poor bioavailability and the selectivity of drugs. Several nanosized delivery systems have already proved their effectiveness in animal models for the treatment and prophylaxis of malaria. A number of strategies to deliver antimalarials using nanocarriers and the mechanisms that facilitate their targeting to Plasmodium spp.-infected cells are discussed in this review. Taking into account the peculiarities of malaria parasites, the focus is placed particularly on lipid-based (e.g., liposomes, solid lipid nanoparticles and nano and microemulsions) and polymer-based nanocarriers (nanocapsules and nanospheres). This review emphasizes the main requirements for developing new nanotechnology-based carriers as a promising choice in malaria treatment, especially in the case of severe cerebral malaria.

Chapter 5. Potential contribution of sero-epidemiological analysis for monitoring malaria control and elimination: historical and current perspectives

Anti-malarial antibody responses represent an individual's history of exposure to the disease and, as age sero-conversion rates, reflect cumulative malaria exposure in a population. As such these antibody responses are an alternate measure of malaria transmission intensity and have potential in evaluating changes in exposure. This approach was used in the 1970s to evaluate malaria control and eradication attempts in a variety of different ecological settings. These historical studies provided a wealth of information on how serological data might be used to interpret control measures. However they were limited by a lack of standardized antigens and reproducible high-throughput assays. Current techniques using recombinant antigens with a range of immunogenicities, high-throughput enzyme-linked immunosorbent assays (ELISA) and statistical analysis allow a more robust examination of how serological parameters can be used to evaluate factors affecting malaria transmission. Here we present a review of the historical data and use it to assess the serological contribution to monitoring malaria elimination.

Plasmodium falciparum drug resistance in Madagascar: facing the spread of unusual pfdhfr and pfmdr-1 haplotypes and the decrease of dihydroartemisinin susceptibility

The aim of this study was to provide the first comprehensive spatiotemporal picture of Plasmodium falciparum resistance in various geographic areas in Madagascar. Additional data about the antimalarial resistance in the neighboring islands of the Comoros archipelago were also collected. We assessed the prevalence of pfcrt, pfmdr-1, pfdhfr, and pfdhps mutations and the pfmdr-1 gene copy number in 1,596 P. falciparum isolates collected in 26 health centers (20 in Madagascar and 6 in the Comoros Islands) from 2006 to 2008. The in vitro responses to a panel of drugs by 373 of the parasite isolates were determined. The results showed (i) unusual profiles of chloroquine susceptibility in Madagascar, (ii) a rapid rise in the frequency of parasites with both the pfdhfr and the pfdhps mutations, (iii) the alarming emergence of the single pfdhfr 164L genotype, and (iv) the progressive loss of the most susceptible isolates to artemisinin derivatives. In the context of the implementation of the new national policy for the fight against malaria, continued surveillance for the detection of P. falciparum resistance in the future is required.

Ecogeographic genetic epidemiology

Complex diseases such as cancer and heart disease result from interactions between an individual's genetics and environment, i.e. their human ecology. Rates of complex diseases have consistently demonstrated geographic patterns of incidence, or spatial "clusters" of increased incidence relative to the general population. Likewise, genetic subpopulations and environmental influences are not evenly distributed across space. Merging appropriate methods from genetic epidemiology, ecology and geography will provide a more complete understanding of the spatial interactions between genetics and environment that result in spatial patterning of disease rates. Geographic information systems (GIS), which are tools designed specifically for dealing with geographic data and performing spatial analyses to determine their relationship, are key to this kind of data integration. Here the authors introduce a new interdisciplinary paradigm, ecogeographic genetic epidemiology, which uses GIS and spatial statistical analyses to layer genetic subpopulation and environmental data with disease rates and thereby discern the complex gene-environment interactions which result in spatial patterns of incidence.

Social and environmental malaria risk factors in urban areas of Ouagadougou, Burkina Faso

BACKGROUND

Despite low endemicity, malaria remains a major health problem in urban areas where a high proportion of fevers are presumptively treated using anti-malarial drugs. Low acquired malaria immunity, behaviour of city-dwellers, access to health care and preventive interventions, and heterogenic suitability of urban ecosystems for malaria transmission contribute to the complexity of the malaria epidemiology in urban areas.

METHODS

The study was designed to identify the determinants of malaria transmission estimated by the prevalence of anti-circumsporozoite (CSP) antibodies, the prevalence and density of Plasmodium falciparum infection, and the prevalence of malarial disease in areas of Ouagadougou, Burkina-Faso. Thick blood smears, dried blood spots and clinical status have been collected from 3,354 randomly chosen children aged 6 months to 12 years using two cross-sectional surveys (during the dry and rainy seasons) in eight areas from four ecological strata defined according to building density and land tenure (regular versus irregular). Demographic characteristics, socio-economic information, and sanitary and environmental data concerning the children or their households were simultaneously collected. Dependent variables were analysed using mixed multivariable models with random effects, taking into account the clustering of participants within compounds and areas.

RESULTS

Overall prevalences of CSP-antibodies and P. falciparum infections were 7.7% and 16.6% during the dry season, and 12.4% and 26.1% during the rainy season, respectively, with significant differences according to ecological strata. Malaria risk was significantly higher among children who i) lived in households with lower economic or education levels, iii) near the hydrographic network, iv) in sparsely built-up areas, v) in irregularly built areas, vi) who did not use a bed net, vii) were sampled during the rainy season or ii) had traveled outside of Ouagadougou.

CONCLUSION

Malaria control should be focused in areas which are irregularly or sparsely built-up or near the hydrographic network. Furthermore, urban children would benefit from preventive interventions (e.g. anti-vectorial devices or chemoprophylaxis) aimed at reducing malaria risk during and after travel in rural areas.

Modelling the impact of artemisinin combination therapy and long-acting treatments on malaria transmission intensity

BACKGROUND

Artemisinin derivatives used in recently introduced combination therapies (ACTs) for Plasmodium falciparum malaria significantly lower patient infectiousness and have the potential to reduce population-level transmission of the parasite. With the increased interest in malaria elimination, understanding the impact on transmission of ACT and other antimalarial drugs with different pharmacodynamics becomes a key issue. This study estimates the reduction in transmission that may be achieved by introducing different types of treatment for symptomatic P. falciparum malaria in endemic areas.

METHODS AND FINDINGS

We developed a mathematical model to predict the potential impact on transmission outcomes of introducing ACT as first-line treatment for uncomplicated malaria in six areas of varying transmission intensity in Tanzania. We also estimated the impact that could be achieved by antimalarials with different efficacy, prophylactic time, and gametocytocidal effects. Rates of treatment, asymptomatic infection, and symptomatic infection in the six study areas were estimated using the model together with data from a cross-sectional survey of 5,667 individuals conducted prior to policy change from sulfadoxine-pyrimethamine to ACT. The effects of ACT and other drug types on gametocytaemia and infectiousness to mosquitoes were independently estimated from clinical trial data. Predicted percentage reductions in prevalence of infection and incidence of clinical episodes achieved by ACT were highest in the areas with low initial transmission. A 53% reduction in prevalence of infection was seen if 100% of current treatment was switched to ACT in the area where baseline slide-prevalence of parasitaemia was lowest (3.7%), compared to an 11% reduction in the highest-transmission setting (baseline slide prevalence = 57.1%). Estimated percentage reductions in incidence of clinical episodes were similar. The absolute size of the public health impact, however, was greater in the highest-transmission area, with 54 clinical episodes per 100 persons per year averted compared to five per 100 persons per year in the lowest-transmission area. High coverage was important. Reducing presumptive treatment through improved diagnosis substantially reduced the number of treatment courses required per clinical episode averted in the lower-transmission settings although there was some loss of overall impact on transmission. An efficacious antimalarial regimen with no specific gametocytocidal properties but a long prophylactic time was estimated to be more effective at reducing transmission than a short-acting ACT in the highest-transmission setting.

CONCLUSIONS

Our results suggest that ACTs have the potential for transmission reductions approaching those achieved by insecticide-treated nets in lower-transmission settings. ACT partner drugs and nonartemisinin regimens with longer prophylactic times could result in a larger impact in higher-transmission settings, although their long term benefit must be evaluated in relation to the risk of development of parasite resistance.