The public health impact and cost-effectiveness of the R21/Matrix-M malaria vaccine: a mathematical modelling study

BACKGROUND

The R21/Matrix-M vaccine has demonstrated high efficacy against Plasmodium falciparum clinical malaria in children in sub-Saharan Africa. Using trial data, we aimed to estimate the public health impact and cost-effectiveness of vaccine introduction across sub-Saharan Africa.

METHODS

We fitted a semi-mechanistic model of the relationship between anti-circumsporozoite protein antibody titres and vaccine efficacy to data from 3 years of follow-up in the phase 2b trial of R21/Matrix-M in Nanoro, Burkina Faso. We validated the model by comparing predicted vaccine efficacy to that observed over 12-18 months in the phase 3 trial. Integrating this framework within a mathematical transmission model, we estimated the cases, malaria deaths, and disability-adjusted life-years (DALYs) averted and cost-effectiveness over a 15-year time horizon across a range of transmission settings in sub-Saharan Africa. Cost-effectiveness was estimated incorporating the cost of vaccine introduction (dose, consumables, and delivery) relative to existing interventions at baseline. We report estimates at a median of 20% parasite prevalence in children aged 2-10 years (PfPR2-10) and ranges from 3% to 65% PfPR2-10.

FINDINGS

Anti-circumsporozoite protein antibody titres were found to satisfy the criteria for a surrogate of protection for vaccine efficacy against clinical malaria. Age-based implementation of a four-dose regimen of R21/Matrix-M vaccine was estimated to avert 181 825 (range 38 815-333 491) clinical cases per 100 000 fully vaccinated children in perennial settings and 202 017 (29 868-405 702) clinical cases per 100 000 fully vaccinated children in seasonal settings. Similar estimates were obtained for seasonal or hybrid implementation. Under an assumed vaccine dose price of US$3, the incremental cost per clinical case averted was $7 (range 4-48) in perennial settings and $6 (3-63) in seasonal settings and the incremental cost per DALY averted was $34 (29-139) in perennial settings and $30 (22-172) in seasonal settings, with lower cost-effectiveness ratios in settings with higher PfPR2-10.

INTERPRETATION

Introduction of the R21/Matrix-M malaria vaccine could have a substantial public health benefit across sub-Saharan Africa.

FUNDING

The Wellcome Trust, the Bill & Melinda Gates Foundation, the UK Medical Research Council, the European and Developing Countries Clinical Trials Partnership 2 and 3, the NIHR Oxford Biomedical Research Centre, and the Serum Institute of India, Open Philanthropy.

Seasonal vaccination with RTS,S/AS01E vaccine with or without seasonal malaria chemoprevention in children up to the age of 5 years in Burkina Faso and Mali: a double-blind, randomised, controlled, phase 3 trial

BACKGROUND

Seasonal vaccination with the RTS,S/AS01E vaccine combined with seasonal malaria chemoprevention (SMC) prevented malaria in young children more effectively than either intervention given alone over a 3 year period. The objective of this study was to establish whether the added protection provided by the combination could be sustained for a further 2 years.

METHODS

This was a double-blind, individually randomised, controlled, non-inferiority and superiority, phase 3 trial done at two sites: the Bougouni district and neighbouring areas in Mali and Houndé district, Burkina Faso. Children who had been enrolled in the initial 3-year trial when aged 5-17 months were initially randomly assigned individually to receive SMC with sulphadoxine-pyrimethamine and amodiaquine plus control vaccines, RTS,S/AS01E plus placebo SMC, or SMC plus RTS,S/AS01E. They continued to receive the same interventions until the age of 5 years. The primary trial endpoint was the incidence of clinical malaria over the 5-year trial period in both the modified intention-to-treat and per-protocol populations. Over the 5-year period, non-inferiority was defined as a 20% increase in clinical malaria in the RTS,S/AS01E-alone group compared with the SMC alone group. Superiority was defined as a 12% difference in the incidence of clinical malaria between the combined and single intervention groups. The study is registered with ClinicalTrials.gov, NCT04319380, and is complete.

FINDINGS

In April, 2020, of 6861 children originally recruited, 5098 (94%) of the 5433 children who completed the initial 3-year follow-up were re-enrolled in the extension study. Over 5 years, the incidence of clinical malaria per 1000 person-years at risk was 313 in the SMC alone group, 320 in the RTS,S/AS01E-alone group, and 133 in the combined group. The combination of RTS,S/AS01E and SMC was superior to SMC (protective efficacy 57·7%, 95% CI 53·3 to 61·7) and to RTS,S/AS01E (protective efficacy 59·0%, 54·7 to 62·8) in preventing clinical malaria. RTS,S/AS01E was non-inferior to SMC (hazard ratio 1·03 [95% CI 0·95 to 1·12]). The protective efficacy of the combination versus SMC over the 5-year period of the study was very similar to that seen in the first 3 years with the protective efficacy of the combination versus SMC being 57·7% (53·3 to 61·7) and versus RTS/AS01E-alone being 59·0% (54·7 to 62·8). The comparable figures for the first 3 years of the study were 62·8% (58·4 to 66·8) and 59·6% (54·7 to 64·0%), respectively. Hospital admissions for WHO-defined severe malaria were reduced by 66·8% (95% CI 40·3 to 81·5), for malarial anaemia by 65·9% (34·1 to 82·4), for blood transfusion by 68·1% (32·6 to 84·9), for all-cause deaths by 44·5% (2·8 to 68·3), for deaths excluding external causes or surgery by 41·1% (-9·2 to 68·3), and for deaths from malaria by 66·8% (-2·7 to 89·3) in the combined group compared with the SMC alone group. No safety signals were detected.

INTERPRETATION

Substantial protection against malaria was sustained over 5 years by combining seasonal malaria vaccination with seasonal chemoprevention, offering a potential new approach to malaria control in areas with seasonal malaria transmission.

FUNDING

UK Joint Global Health Trials and PATH's Malaria Vaccine Initiative (through a grant from the Bill & Melinda Gates Foundation).

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Prevalence of Plasmodium falciparum haplotypes associated with resistance to sulfadoxine-pyrimethamine and amodiaquine before and after upscaling of seasonal malaria chemoprevention in seven African countries: a genomic surveillance study

BACKGROUND

Seasonal malaria chemoprevention is used in 13 countries in the Sahel region of Africa to prevent malaria in children younger than 5 years. Resistance of Plasmodium falciparum to seasonal malaria chemoprevention drugs across the region is a potential threat to this intervention.

METHODS

Between December, 2015, and March, 2016, and between December, 2017, and March, 2018, immediately following the 2015 and 2017 malaria transmission seasons, community surveys were done among children younger than 5 years and individuals aged 10-30 years in districts implementing seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine in Burkina Faso, Chad, Guinea, Mali, Nigeria, Niger and The Gambia. Dried blood samples were collected and tested for P falciparum DNA by PCR. Resistance-associated haplotypes of the P falciparum genes crt, mdr1, dhfr, and dhps were identified by quantitative PCR and sequencing of isolates from the collected samples, and survey-weighted prevalence and prevalence ratio between the first and second surveys were estimated for each variant.

FINDINGS

5130 (17·5%) of 29 274 samples from 2016 and 2176 (7·6%) of 28 546 samples from 2018 were positive for P falciparum on quantitative PCR. Among children younger than 5 years, parasite carriage decreased from 2844 of 14 345 samples (19·8% [95% CI 19·2-20·5]) in 2016 to 801 of 14 019 samples (5·7% [5·3-6·1]) in 2018 (prevalence ratio 0·27 [95% CI 0·24-0·31], p<0·0001). Genotyping found no consistent evidence of increasing prevalence of amodiaquine resistance-associated variants of crt and mdr1 between 2016 and 2018. The dhfr haplotype IRN (consisting of 51Ile-59Arg-108Asn) was common at both survey timepoints, but the dhps haplotype ISGEAA (431Ile-436Ser-437Gly-540Glu-581Ala-613Ala), crucial for resistance to sulfadoxine-pyrimethamine, was always rare. Parasites carrying amodiaquine resistance-associated variants of both crt and mdr1 together with dhfr IRN and dhps ISGEAA occurred in 0·05% of isolates. The emerging dhps haplotype VAGKGS (431Val-436Ala-437Gly-540Lys-581Gly-613Ser) was present in four countries.

INTERPRETATION

In seven African countries, evidence of a significant reduction in parasite carriage among children receiving seasonal malaria chemoprevention was found 2 years after intervention scale-up. Combined resistance-associated haplotypes remained rare, and seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine is expected to retain effectiveness. The threat of future erosion of effectiveness due to dhps variant haplotypes requires further monitoring.

FUNDING

Unitaid.

Pf7: an open dataset of Plasmodium falciparum genome variation in 20,000 worldwide samples

We describe the MalariaGEN Pf7 data resource, the seventh release of Plasmodium falciparum genome variation data from the MalariaGEN network.  It comprises over 20,000 samples from 82 partner studies in 33 countries, including several malaria endemic regions that were previously underrepresented.  For the first time we include dried blood spot samples that were sequenced after selective whole genome amplification, necessitating new methods to genotype copy number variations.  We identify a large number of newly emerging crt mutations in parts of Southeast Asia, and show examples of heterogeneities in patterns of drug resistance within Africa and within the Indian subcontinent.  We describe the profile of variations in the C-terminal of the csp gene and relate this to the sequence used in the RTS,S and R21 malaria vaccines.  Pf7 provides high-quality data on genotype calls for 6 million SNPs and short indels, analysis of large deletions that cause failure of rapid diagnostic tests, and systematic characterisation of six major drug resistance loci, all of which can be freely downloaded from the MalariaGEN website.

Seasonal use case for the RTS,S/AS01 malaria vaccine: a mathematical modelling study

BACKGROUND

A 2021 clinical trial of seasonal RTS,S/AS01_E (RTS,S) vaccination showed that vaccination was non-inferior to seasonal malaria chemoprevention (SMC) in preventing clinical malaria. The combination of these two interventions provided significant additional protection against clinical and severe malaria outcomes. Projections of the effect of this novel approach to RTS,S vaccination in seasonal transmission settings for extended timeframes and across a range of epidemiological settings are needed to inform policy recommendations.

METHODS

We used a mathematical, individual-based model of malaria transmission that was fitted to data on the relationship between entomological inoculation rate and parasite prevalence, clinical disease, severe disease, and deaths from multiple sites across Africa. The model was validated with results from a phase 3b trial assessing the effect of SV-RTS,S in Mali and Burkina Faso. We developed three intervention efficacy models with varying degrees and durations of protection for our population-level modelling analysis to assess the potential effect of an RTS,S vaccination schedule based on age (doses were delivered to children aged 6 months, 7·5 months, and 9 months for the first three doses, and at 27 months of age for the fourth dose) or season (children aged 5-17 months at the time of first vaccination received the first three doses in the 3 months preceding the transmission season, with any subsequent doses up to five doses delivered annually) in seasonal transmission settings both in the absence and presence of SMC with sulfadoxine-pyrimethamine plus amodiaquine. This is modelled as a full therapeutic course delivered every month for four or five months of the peak in transmission season. Estimates of cases and deaths averted in a population of 100 000 children aged 0-5 years were calculated over a 15-year time period for a range of levels of malaria transmission intensity (Plasmodium falciparum parasite prevalence in children aged 2-10 years between 10% and 65%) and over two west Africa seasonality archetypes.

FINDINGS

Seasonally targeting RTS,S resulted in greater absolute reductions in malaria cases and deaths compared with an age-based strategy, averting an additional 14 000-47 000 cases per 100 000 children aged 5 years and younger over 15 years, dependent on seasonality and transmission intensity. We predicted that adding seasonally targeted RTS,S to SMC would reduce clinical incidence by up to an additional 42 000-67 000 cases per 100 000 children aged 5 years and younger over 15 years compared with SMC alone. Transmission season duration was a key determinant of intervention effect, with the advantage of adding RTS,S to SMC predicted to be smaller with shorter transmission seasons.

INTERPRETATION

RTS,S vaccination in seasonal settings could be a valuable additional tool to existing interventions, with seasonal delivery maximising the effect relative to an age-based approach. Decisions surrounding deployment strategies of RTS,S in such settings will need to consider the local and regional variations in seasonality, current rates of other interventions, and potential achievable RTS,S coverage.

FUNDING

UK Medical Research Council, UK Foreign Commonwealth & Development Office, The Wellcome Trust, and The Royal society.

The Strategy of Paratransgenesis for the Control of Malaria Transmission

Insect-borne diseases are responsible for important burdens on health worldwide particularly in Africa. Malaria alone causes close to half a million deaths every year, mostly in developing, tropical and subtropical countries, with 94% of the global deaths in 2019 occurring in the WHO African region. With several decades, vector control measures have been fundamental to fight against malaria. Considering the spread of resistance to insecticides in mosquitoes and to drugs in parasites, the need for novel strategies to inhibit the transmission of the disease is pressing. In recent years, several studies have focused on the interaction of malaria parasites, bacteria and their insect vectors. Their findings suggested that the microbiota of mosquitoes could be used to block Plasmodium transmission. A strategy, termed paratransgenesis, aims to interfere with the development of malaria parasites within their vectors through genetically-modified microbes, which produce antimalarial effectors inside the insect host. Here we review the progress of the paratransgenesis approach. We provide a historical perspective and then focus on the choice of microbial strains and on genetic engineering strategies. We finally describe the different steps from laboratory design to field implementation to fight against malaria.

Delivery of seasonal malaria chemoprevention with enhanced infection prevention and control measures during the COVID-19 pandemic in Nigeria, Burkina Faso and Chad: a cross-sectional study

Background

Seasonal malaria chemoprevention (SMC) is a WHO-recommended intervention for children aged 3–59 months living in areas of high malaria transmission to provide protection against malaria during the rainy season. Operational guidelines were developed, based on WHO guidance, to support countries to mitigate the risk of coronavirus disease 2019 (COVID-19) transmission within communities and among community distributors when delivering SMC.

Methods

A cross-sectional study to determine adherence to infection prevention and control (IPC) measures during two distribution cycles of SMC in Nigeria, Chad and Burkina Faso. Community distributors were observed receiving equipment and delivering SMC. Adherence across six domains was calculated as the proportion of indications in which the community distributor performed the correct action. Focus group discussions were conducted with community distributors to understand their perceptions of the IPC measures and barriers and facilitators to adherence.

Results

Data collectors observed community distributors in Nigeria (n = 259), Burkina Faso (n = 252) and Chad (n = 266) receiving IPC equipment and delivering SMC. Adherence to IPC indications varied. In all three countries, adherence to mask use was the highest (ranging from 73.3% in Nigeria to 86.9% in Burkina Faso). Adherence to hand hygiene for at least 30 s was low (ranging from 3.6% in Nigeria to 10.3% in Burkina Faso) but increased substantially when excluding the length of time spent hand washing (ranging from 36.7% in Nigeria to 61.4% in Burkina Faso). Adherence to safe distancing in the compound ranged from 5.4% in Chad to 16.4% in Nigeria. In Burkina Faso and Chad, where disinfection wipes widely available compliance with disinfection of blister packs for SMC was low (17.4% in Burkina Faso and 16.9% in Chad). Community distributors generally found the IPC measures acceptable, however there were barriers to optimal hand hygiene practices, cultural norms made social distancing difficult to adhere to and caregivers needed assistance to administer the first dose of SMC.

Conclusion

Adherence to IPC measures for SMC delivery during the COVID-19 pandemic varied across domains of IPC, but was largely insufficient, particularly for hand hygiene and safe distancing. Improvements in provision of protective equipment, early community engagement and adaptations to make IPC measures more feasible to implement could increase adherence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04091-z.

Impact of mass administration of azithromycin as a preventive treatment on the prevalence and resistance of nasopharyngeal carriage of Staphylococcus aureus

Staphylococcus aureus is a major cause of serious illness and death in children, indicating the need to monitor prevalent strains, particularly in the vulnerable pediatric population. Nasal carriage of S. aureus is important as carriers have an increased risk of serious illness due to systemic invasion by this pathogen and can transmit the infection. Recent studies have demonstrated the effectiveness of azithromycin in reducing the prevalence of nasopharyngeal carrying of pneumococci, which are often implicated in respiratory infections in children. However, very few studies of the impact of azithromycin on staphylococci have been undertaken. During a clinical trial under taken in 2016, nasal swabs were collected from 778 children aged 3 to 59 months including 385 children who were swabbed before administration of azithromycin or placebo and 393 after administration of azithromycin or placebo. Azithromycin was given in a dose of 100 mg for three days, together with the antimalarials sulfadoxine-pyrimethamine and amodiaquine, on four occasions at monthly intervals during the malaria transmission season. These samples were cultured for S. aureus as well as for the pneumococcus. The S. aureus isolates were tested for their susceptibility to azithromycin (15 g), penicillin (10 IU), and cefoxitine (30 g) (Oxoid Ltd). S. aureus was isolated from 13.77% (53/385) swabs before administration of azithromycin and from 20.10% (79/393) six months after administration (PR = 1.46 [1.06; 2.01], p = 0.020). Azithromycin resistance found in isolates of S. aureus did not differ significantly before and after intervention (26.42% [14/53] vs 16.46% [13/79], (PR = 0.62 [0.32; 1.23], p = 0.172). Penicillin resistance was very pronounced, 88.68% and 96.20% in pre-intervention and in post-intervention isolates respectively, but very little Methicillin Resistance (MRSA) was detected (2 cases before and 2 cases after intervention). Monitoring antibiotic resistance in S. aureus and other bacteria is especially important in Burkina Faso due to unregulated consumption of antibiotics putting children and others at risk.

Combining malaria vaccination with chemoprevention: a promising new approach to malaria control

Malaria control has stalled in a number of African countries and novel approaches to malaria control are needed for these areas. The encouraging results of a recent trial conducted in young children in Burkina Faso and Mali in which a combination of the RTS,S/AS01E malaria vaccine and seasonal malaria chemoprevention led to a substantial reduction in clinical cases of malaria, severe malaria, and malaria deaths compared with the administration of either intervention given alone suggests that there may be other epidemiological/clinical situations in which a combination of malaria vaccination and chemoprevention could be beneficial. Some of these potential opportunities are considered in this paper. These include combining vaccination with intermittent preventive treatment of malaria in infants, with intermittent preventive treatment of malaria in pregnancy (through vaccination of women of child-bearing age before or during pregnancy), or with post-discharge malaria chemoprevention in the management of children recently admitted to hospital with severe anaemia. Other potential uses of the combination are prevention of malaria in children at particular risk from the adverse effects of clinical malaria, such as those with sickle cell disease, and during the final stages of a malaria elimination programme when vaccination could be combined with repeated rounds of mass drug administration. The combination of a pre-erythrocytic stage malaria vaccine with an effective chemopreventive regimen could make a valuable contribution to malaria control and elimination in a variety of clinical or epidemiological situations, and the potential of this approach to malaria control needs to be explored.

Insecticide resistance profiles in malaria vector populations from Sud-Kivu in the Democratic Republic of the Congo

BACKGROUND

Insecticide resistance has become a widespread problem causing a decline in the effectiveness of vector control tools in sub-Saharan Africa. In this situation, ongoing monitoring of vector susceptibility to insecticides is encouraged by the WHO to guide national malaria control programmes. Our study was conducted from April to November 2018 in Tchonka (Sud-Kivu, Democratic Republic of the Congo) and reported primary data on the resistance status of Anopheles funestus and Anopheles gambiae.

METHODS

Insecticide susceptibility bioassays were performed on wild populations of A. funestus and A. gambiae using WHO insecticide-impregnated papers at discriminating concentration. In addition, PCR was performed to identify mosquito species and to detect kdr and ace-1R mutations involved in insecticide resistance.

RESULTS

Bioassay results show resistance to all tested insecticides except pirimiphos-methyl, propoxur, fenitrothion and malathion with a mortality rate ranging from 95.48 to 99.86%. The addition of piperonyl butoxide (PBO) increased the susceptibility of vectors to deltamethrin and alpha-cypermethrin by exhibiting a mortality ranging from 91.50 to 95.86%. The kdr mutation was detected at high frequencies (approximately 0.98) within A. gambiae while ace-1R was not detected.

CONCLUSIONS

This study provides useful data on the insecticide resistance profiles of malaria vector populations to better manage vector control. Our results highlight that, despite the high level of resistance, organophosphorus compounds and pyrethroids + PBO remain effective against the vectors.

An open dataset of Plasmodium falciparum genome variation in 7,000 worldwide samples

MalariaGEN is a data-sharing network that enables groups around the world to work together on the genomic epidemiology of malaria. Here we describe a new release of curated genome variation data on 7,000 Plasmodium falciparum samples from MalariaGEN partner studies in 28 malaria-endemic countries. High-quality genotype calls on 3 million single nucleotide polymorphisms (SNPs) and short indels were produced using a standardised analysis pipeline. Copy number variants associated with drug resistance and structural variants that cause failure of rapid diagnostic tests were also analysed.  Almost all samples showed genetic evidence of resistance to at least one antimalarial drug, and some samples from Southeast Asia carried markers of resistance to six commonly-used drugs. Genes expressed during the mosquito stage of the parasite life-cycle are prominent among loci that show strong geographic differentiation. By continuing to enlarge this open data resource we aim to facilitate research into the evolutionary processes affecting malaria control and to accelerate development of the surveillance toolkit required for malaria elimination.

An open dataset of Plasmodium falciparum genome variation in 7,000 worldwide samples

MalariaGEN is a data-sharing network that enables groups around the world to work together on the genomic epidemiology of malaria. Here we describe a new release of curated genome variation data on 7,000 Plasmodium falciparum samples from MalariaGEN partner studies in 28 malaria-endemic countries. High-quality genotype calls on 3 million single nucleotide polymorphisms (SNPs) and short indels were produced using a standardised analysis pipeline. Copy number variants associated with drug resistance and structural variants that cause failure of rapid diagnostic tests were also analysed.  Almost all samples showed genetic evidence of resistance to at least one antimalarial drug, and some samples from Southeast Asia carried markers of resistance to six commonly-used drugs. Genes expressed during the mosquito stage of the parasite life-cycle are prominent among loci that show strong geographic differentiation. By continuing to enlarge this open data resource we aim to facilitate research into the evolutionary processes affecting malaria control and to accelerate development of the surveillance toolkit required for malaria elimination.

A prebiotic-enhanced lipid-based nutrient supplement (LNSp) increases Bifidobacterium relative abundance and enhances short-chain fatty acid production in simulated colonic microbiota from undernourished infants

Undernutrition remains a public health problem in the developing world with an attributable under-five death proportion of 45%. Lower gut microbiota diversity and poor metabolic output are associated with undernutrition and new therapeutic paths may come from steering gut microbiota composition and functionality. Using a dynamic gut model, the Simulator of Human Intestinal Microbial Ecosystem (SHIME®), we investigated the effect of a lipid-based nutrient supplement enriched with prebiotics (LNSp), compared to LNS alone and control treatment, on the composition and metabolic functionality of fecal microbiota from three infants suffering from undernutrition. LNS elicited a significant increase in acetate and branched-chain fatty acid production, and a higher relative abundance of the genera Prevotella, Megasphaera, Acinetobacter, Acidaminococcus and Pseudomonas. In contrast, LNSp treatment resulted in a significant 9-fold increase in Bifidobacterium relative abundance and a decrease in that of potential pathogens and detrimental bacteria such as Enterobacteriaceae spp. and Bilophila sp. Moreover, the LNSp treatment resulted in a significantly higher production of acetate, butyrate and propionate, as compared to control and LNS. Our results suggest that provision of prebiotic-enhanced LNS to undernourished children could be a possible strategy to steer the microbiota toward a more beneficial composition and metabolic activity. Further in vivo investigations are needed to assess these effects and their repercussion on nutritional status.

Seasonal malaria vaccination: protocol of a phase 3 trial of seasonal vaccination with the RTS,S/AS01E vaccine, seasonal malaria chemoprevention and the combination of vaccination and chemoprevention

INTRODUCTION

Seasonal malaria chemoprevention (SMC), with sulphadoxine-pyrimethamine plus amodiaquine (SP+AQ) is effective but does not provide complete protection against clinical malaria. The RTS,S/AS01_E malaria vaccine provides a high level of protection shortly after vaccination, but this wanes rapidly. Such a vaccine could be an alternative or additive to SMC. This trial aims to determine whether seasonal vaccination with RTS,S/AS01_E vaccine could be an alternative to SMC and whether a combination of the two interventions would provide added benefits.

METHODS AND ANALYSIS

This is an individually randomised, double-blind, placebo-controlled trial. 5920 children aged 5-17 months were enrolled in April 2017 in Mali and Burkina Faso. Children in group 1 received three priming doses of RTS,S/AS01_E vaccine before the start of the 2017 malaria transmission season and a booster dose at the beginning of two subsequent transmission seasons. In addition, they received SMC SP+AQ placebo on four occasions each year. Children in group 2 received three doses of rabies vaccine in year 1 and hepatitis A vaccine in years 2 and 3 together with four cycles of SMC SP+AQ each year. Children in group 3 received RTS,S/AS01_E vaccine and four courses of SMC SP+AQ. Incidence of clinical malaria is determined by case detection at health facilities. Weekly active surveillance for malaria is undertaken in a randomly selected subset of children. The prevalence of malaria is measured in surveys at the end of each transmission season. The primary endpoint is the incidence of clinical malaria confirmed by a positive blood film with a minimum parasite density of 5000 /µL. Primary analysis will be by modified intention to treat defined as children who have received the first dose of the malaria or control vaccine.

ETHICS AND DISSEMINATION

The protocol was approved by the national ethics committees of Mali and Burkina Faso and the London School of Hygiene and Tropical Medicine. The results will be presented to all stakeholders and published in open access journals.

TRIAL REGISTRATION NUMBER

NCT03143218; Pre-results.

Antibody Persistence at the Population Level 5 Years After Mass Vaccination With Meningococcal Serogroup A Conjugate Vaccine (PsA-TT) in Burkina Faso: Need for a Booster Campaign?

Background

In Burkina Faso, serogroup A meningococcal (NmA) conjugate vaccine (PsA-TT, MenAfriVac) was introduced through a mass campaign in children and adults in December 2010. Similar to a serological survey in 2011, we followed population-level antibody persistence for 5 years after the campaign and estimated time of return to previously-published pre-vaccination levels.

Methods

We conducted 2 cross-sectional surveys in 2013 and early 2016, including representative samples (N = 600) of the general population of Bobo-Dioulasso, Burkina Faso. Serum bactericidal antibody titers (rabbit complement) were measured against NmA reference strain F8236 (SBA-ref), NmA strain 3125 (SBA-3125), and NmA-specific immunoglobulin G (IgG) concentrations.

Results

During the 2016 survey, in different age groups between 6 and 29 years, the relative changes in geometric means compared to 2011 values were greater among younger age groups. They were between -87% and -43% for SBA-ref; -99% and -78% for SBA-3125; and -89% and -63% for IgG. In linear extrapolation of age-specific geometric means from 2013 to 2016, among children aged 1-4 years at the time of the PsA-TT campaign, a return to pre-vaccination levels should be expected after 12, 8, and 6 years, respectively, according to SBA-ref, SBA-3125, and IgG. Among older individuals, complete return to baseline is expected at the earliest after 11 years (SBA-ref and SBA-3125) or 9 years (IgG).

Conclusions

Based on SBA-3125, a booster campaign after 8 years would be required to sustain direct immune protection for children aged 1-4 years during the PsA-TT campaign. Antibodies persisted longer in older age groups.

Immunogenicity and Reactogenicity of 13-Valent Pneumococcal Conjugate Vaccine Among Infants, Toddlers, and Children in Western Burkina Faso: Results From a Clinical Trial of Alternative Immunization Schedules

BACKGROUND

Many African countries have introduced pneumococcal conjugate vaccine (PCV) into their routine immunization program to reduce the burden of morbidity and death that results from Streptococcus pneumoniae infection, yet immunogenicity and reactogenicity data from the region are limited for the 2 available PCV products.

METHODS

We conducted a randomized trial of 13-valent PCV (PCV13) in Bobo-Dioulasso, Burkina Faso. Infants received 3 doses of PCV at 6, 10, and 14 weeks of age or at 6 weeks, 14 weeks, and 9 months of age; toddlers received 2 doses 2 months apart or 1 dose beginning at 12 to 15 months of age; and children received 1 dose between 2 and 4 years of age. We measured each participant's serotype-specific serum immunoglobulin G concentration and opsonophagocytic activity before and after vaccination. For each age group, we compared immune responses between study arms and between the standard schedule in our study and the PCV13-licensing trials.

RESULTS

In total, 280 infants, 302 toddlers, and 81 children were assigned randomly and underwent vaccination; 268, 235, and 77 of them completed follow-up, respectively. PCV13 resulted in low reactogenicity in all the study arms. The vaccine elicited a strong primary immune response in infants after 2 or more doses and in children aged 1 to 4 years after 1 dose. Infants who received a booster dose exhibited a robust memory response. Immunogenicity was higher than or comparable to that observed in the PCV13-licensing trials for a majority of serotypes in all 3 age groups.

CONCLUSIONS

PCV13 has a satisfactory immunogenicity and reactogenicity profile in this population. Our findings will help support decision making by countries regarding their infant and catch-up vaccination schedules.

Effect of Adding Azithromycin to Seasonal Malaria Chemoprevention

BACKGROUND

Mass administration of azithromycin for trachoma control led to a sustained reduction in all-cause mortality among Ethiopian children. Whether the addition of azithromycin to the monthly sulfadoxine-pyrimethamine plus amodiaquine used for seasonal malaria chemoprevention could reduce mortality and morbidity among African children was unclear.

METHODS

We randomly assigned children 3 to 59 months of age, according to household, to receive either azithromycin or placebo, together with sulfadoxine-pyrimethamine plus amodiaquine, during the annual malaria-transmission season in Burkina Faso and Mali. The drug combinations were administered in four 3-day cycles, at monthly intervals, for three successive seasons. The primary end point was death or hospital admission for at least 24 hours that was not due to trauma or elective surgery. Data were recorded by means of active and passive surveillance.

RESULTS

In July 2014, a total of 19,578 children were randomly assigned to receive seasonal malaria chemoprevention plus either azithromycin (9735 children) or placebo (9843 children); each year, children who reached 5 years of age exited the trial and new children were enrolled. In the intention-to-treat analysis, the overall number of deaths and hospital admissions during three malaria-transmission seasons was 250 in the azithromycin group and 238 in the placebo group (events per 1000 child-years at risk, 24.8 vs. 23.5; incidence rate ratio, 1.1; 95% confidence interval [CI], 0.88 to 1.3). Results were similar in the per-protocol analysis. The following events occurred less frequently with azithromycin than with placebo: gastrointestinal infections (1647 vs. 1985 episodes; incidence rate ratio, 0.85; 95% CI, 0.79 to 0.91), upper respiratory tract infections (4893 vs. 5763 episodes; incidence rate ratio, 0.85; 95% CI, 0.81 to 0.90), and nonmalarial febrile illnesses (1122 vs. 1424 episodes; incidence rate ratio, 0.79; 95% CI, 0.73 to 0.87). The prevalence of malaria parasitemia and incidence of adverse events were similar in the two groups.

CONCLUSIONS

Among children in Burkina Faso and Mali, the addition of azithromycin to the antimalarial agents used for seasonal malaria chemoprevention did not result in a lower incidence of death or hospital admission that was not due to trauma or surgery than antimalarial agents plus placebo, although a lower disease burden was noted with azithromycin than with placebo. (Funded by the Joint Global Health Trials scheme; ClinicalTrials.gov number, NCT02211729.).

OC 8721 WANECAM II – A CLINICAL TRIAL PROGRAMME TO ASSESS SAFETY, EFFICACY AND TRANSMISSION-BLOCKING PROPERTIES OF A NEW ANTIMALARIAL KAF156 (GANAPLACIDE) IN UNCOMPLICATED MALARIA IN WEST AND CENTRAL AFRICA

Background

Despite major progress in the past decade, malaria remains a major public health problem in sub-Saharan Africa. West and Central Africa account for nearly 2/3 of the burden currently attributable to falciparum malaria. Artemisinin-based combination therapies (ACT) are a cornerstone of our strategy for controlling and eventually eliminating malaria. However, reduced responsiveness/resistance to artemisinin derivatives and to ACTs, an increasing problem in South-East Asia is a major concern. It is of utmost importance to develop new antimalarial drugs from novel chemical classes that can replace ACTs. KAF156, an imidazolepiperazine, is a leading candidate in the antimalarial drug development pipeline. Combination of KAF156 with a Solid Dispersion Formulation of lumefantrine (LUM-SDF) is expected to be fast acting, fully curative, improve patient adherence and can potentially reduce malaria transmission.

Methods

WANECAM II proposes to advance the clinical development of KAF156 through clinical trials in adults and children, with integrated capacity building and infrastructure development activities. The trial programme will be undertaken in the context of networking, team-building, leadership development and community engagement schemes that will involve intra-European, European-African and intra-African collaborative activities. WANECAM II will accelerate the clinical study of children less than 2 years of age which are the key target for new antimalarial treatments.

Results

By the end of the project, the results are expected to contribute to the registration of KAF156/LUM-SDF through stringent regulatory health authorities, increase biomedical research capacity in the consortium and effectively promote networking among the respective teams. A new clinical research team in Niger, a grossly underrepresented country in the African research landscape, will be developed and further increase capacity and infrastructure in the consortium.

Conclusion

Providing a new antimalarial drug combination that does not contain an artemisinin derivative and is effective against resistant P. falciparum strains as well as gametocytes and that is likely to be taken in 3 or fewer single doses will be a major advance in the field. The new combination of KAF156 with LUM-SDF is expected to provide such major advance upon successful conclusion of the WANECAM II project.

Evaluation of the effects on the QT-interval of 4 artemisinin-based combination therapies with a correction-free and heart rate-free method

Several antimalarial drugs are known to prolong ventricular repolarization as evidenced by QT/QTc interval prolongation. This can lead to Torsades de Pointes, a potentially lethal ventricular arrhythmia. Whether this is the case with artemisinin-based combination therapies (ACTs) remains uncertain. Assessment of the extent of QTc prolongation with antimalarials is hampered by important variations of heart rate during malaria crises and previous studies have reported highly variable values of QTc prolongations with ACTs. We assessed QTc prolongation with four ACTs, using high quality ECG recording and measurement techniques, during the first episode of malaria in 2,091 African patients enrolled in the WANECAM study which also monitored clinical safety. Using an original and robust method of QTc assessment, independent from heart rate changes and from the method of QT correction, we were able to accurately assess the extent of mean maximum QTc prolongation with the four ACTs tested. There was no evidence of proarrhythmia with any treatment during the study although dihydroartemisinin-piperaquine, artesunate-amodiaquine and artemether-lumefantrine significantly prolonged QTc. The extent of prolongation of ventricular repolarization can be accurately assessed in studies where heart rate changes impede QTc assessment.

Genetically diverse Plasmodium falciparum infections, within-host competition and symptomatic malaria in humans

There is a large genetic diversity of Plasmodium falciparum strains that infect people causing diverse malaria symptoms. This study was carried out to explore the effect of mixed-strain infections and the extent to which some specific P. falciparum variants are associated with particular malaria symptoms. P. falciparum isolates collected during pharmacovigilance study in Nanoro, Burkina Faso were used to determine allelic variation in two polymorphic antigens of the merozoite surface (msp1 and msp2). Overall, parasite density did not increase with additional strains, suggesting the existence of within-host competition. Parasite density was influenced by msp1 allelic families with highest parasitaemia observed in MAD20 allelic family. However, when in mixed infections with allelic family K1, MAD20 could not grow to the same levels as it would alone, suggesting competitive suppression in these mixed infections. Host age was associated with parasite density. Overall, older patients exhibited lower parasite densities than younger patients, but this effect varied with the genetic composition of the isolates for the msp1 gene. There was no effect of msp1 and msp2 allelic family variation on body temperature. Haemoglobin level was influenced by msp2 family with patients harboring the FC27 allele showing lower haemoglobin level than mono-infected individuals by the 3D7 allele. This study provides evidence that P. falciparum genetic diversity influenced the severity of particular malaria symptoms and supports the existence of within-host competition in genetically diverse P. falciparum.

Evaluation of the Antiplasmodial Activity and Lethality of the Leaf Extract of Cassia alata L. (Fabaceae)

OBJECTIVE

Cassia alata L. (Fabaceae), one of the three plants contained in Saye, a polyherbal antimalarial remedy was assessed for its antimalarial potential and safety in mice.

METHODOLOGY

Organic extracts were prepared from the leaves and tested on the D 10 chloroquine-sensitive strain of Plasmodium falciparum using the parasite lactate dehydrogenase assay. The 4 days suppressive test using Plasmodium berghei in mice was used to evaluate the in vivo antiplasmodial activity of the extracts. Animals were treated by oral route, once a day with 50, 100, 250 and 400 mg kg -1 b.wt., of the extracts. The acute toxicity of the extracts was assessed in mice according to Thompson and Weil method. The lethal effects of the extracts on animal's body weight, tissues, biochemical and haematological parameters were determined at 823.5, 1235.5, 1853 and 2779.5 mg kg -1 b.wt., respectively.

RESULTS

The dichloromethane/methane (1:1, v/v) extract of Cassia alata was the most active against Plasmodium falciparum. The mean percent suppression of parasitemia in mice was equal to 22.5, 41.8 and 45.2% at 50, 250 and 400 mg kg -1 b.wt., respectively. No death and no clinically significant changes were recorded in mice. The maximum non-lethal dose was more than 16875 mg kg -1 in animals. No significant changes were observed in body weight, tissues morphology, biochemical and hematological parameters at doses above or equal to 2779.5 mg kg -1 b.wt.

CONCLUSION

The dichloromethane/methanol leaf extract of Cassia alata had a good to moderate in vitro and in vivo antiplasmodial activity and was found to have low toxicity at high doses in tested animals.

Seasonal vaccination against malaria: a potential use for an imperfect malaria vaccine

In many parts of the African Sahel and sub-Sahel, where malaria remains a major cause of mortality and morbidity, transmission of the infection is highly seasonal. Seasonal malaria chemoprevention (SMC), which involves administration of a full course of malaria treatment to young children at monthly intervals during the high transmission season, is proving to be an effective malaria control measure in these areas. However, SMC does not provide complete protection and it is demanding to deliver for both families and healthcare givers. Furthermore, there is a risk of the emergence in the future of resistance to the drugs, sulfadoxine-pyrimethamine and amodiaquine, that are currently being used for SMC. Substantial progress has been made in the development of malaria vaccines during the past decade and one malaria vaccine, RTS,S/AS01, has received a positive opinion from the European Medicines Authority and will soon be deployed in large-scale, pilot implementation projects in sub-Saharan Africa. A characteristic feature of this vaccine, and potentially of some of the other malaria vaccines under development, is that they provide a high level of efficacy during the period immediately after vaccination, but that this wanes rapidly, perhaps because it is difficult to develop effective immunological memory to malaria antigens in subjects exposed previously to malaria infection. A potentially effective way of using malaria vaccines with high initial efficacy but which provide only a short period of protection could be annual, mass vaccination campaigns shortly before each malaria transmission season in areas where malaria transmission is confined largely to a few months of the year.

Plant-Mediated Effects on Mosquito Capacity to Transmit Human Malaria

The ecological context in which mosquitoes and malaria parasites interact has received little attention, compared to the genetic and molecular aspects of malaria transmission. Plant nectar and fruits are important for the nutritional ecology of malaria vectors, but how the natural diversity of plant-derived sugar sources affects mosquito competence for malaria parasites is unclear. To test this, we infected Anopheles coluzzi, an important African malaria vector, with sympatric field isolates of Plasmodium falciparum, using direct membrane feeding assays. Through a series of experiments, we then examined the effects of sugar meals from Thevetia neriifolia and Barleria lupilina cuttings that included flowers, and fruit from Lannea microcarpa and Mangifera indica on parasite and mosquito traits that are key for determining the intensity of malaria transmission. We found that the source of plant sugar meal differentially affected infection prevalence and intensity, the development duration of the parasites, as well as the survival and fecundity of the vector. These effects are likely the result of complex interactions between toxic secondary metabolites and the nutritional quality of the plant sugar source, as well as of host resource availability and parasite growth. Using an epidemiological model, we show that plant sugar source can be a significant driver of malaria transmission dynamics, with some plant species exhibiting either transmission-reducing or -enhancing activities.

Safety and efficacy of re-treatments with pyronaridine-artesunate in African patients with malaria: a substudy of the WANECAM randomised trial

BACKGROUND

Sparse data on the safety of pyronaridine-artesunate after repeated treatment of malaria episodes restrict its clinical use. We therefore compared the safety of pyronaridine-artesunate after treatment of the first episode of malaria versus re-treatment in a substudy analysis.

METHODS

This planned substudy analysis of the randomised, open-label West African Network for Clinical Trials of Antimalarial Drugs (WANECAM) phase 3b/4 trial was done at six health facilities in Mali, Burkina Faso, and Guinea in patients (aged ≥6 months and bodyweight ≥5 kg) with uncomplicated microscopically confirmed Plasmodium spp malaria (parasite density <200 000 per μL blood) and fever or history of fever. The primary safety endpoint was incidence of hepatotoxicity: alanine aminotransferase of greater than five times the upper limit of normal (ULN) or Hy's criteria (alanine aminotransferase or aspartate aminotransferase greater than three times the ULN and total bilirubin more than twice the ULN) after treatment of the first episode of malaria and re-treatment (≥28 days after first treatment) with pyronaridine-artesunate. Pyronaridine-artesunate efficacy was compared with artemether-lumefantrine with the adequate clinical and parasitological response (ACPR) in an intention-to-treat analysis. WANECAM is registered with PACTR.org, number PACTR201105000286876.

FINDINGS

Following first treatment, 13 (1%) of 996 patients had hepatotoxicity (including one [<1%] possible Hy's law case) versus two (1%) of 311 patients on re-treatment (neither a Hy's law case). No evidence was found that pyronaridine-artesunate re-treatment increased safety risk based on laboratory values, reported adverse event frequencies, or electrocardiograph findings. For all first treatment or re-treatment episodes, pyronaridine-artesunate (n=673) day 28 crude ACPR was 92·7% (95% CI 91·0-94·3) versus 80·4% (77·8-83·0) for artemether-lumefantrine (n=671). After exclusion of patients with PCR-confirmed new infections, ACPR was similar on treatment and re-treatment and greater than 95% at day 28 and greater than 91% at day 42 in both treatment groups.

INTERPRETATION

The findings that pyronaridine-artesunate safety and efficacy were similar on first malaria treatment versus re-treatment of subsequent episodes lend support for the wider access to pyronaridine-artesunate as an alternative artemisinin-based combination treatment for malaria in sub-Saharan Africa.

FUNDING

European and Developing Countries Clinical Trial Partnership, Medicines for Malaria Venture (Geneva, Switzerland), UK Medical Research Council, Swedish International Development Cooperation Agency, German Ministry for Education and Research, University Claude Bernard (Lyon, France), Malaria Research and Training Centre (Bamako, Mali), Centre National de Recherche et de Formation sur le Paludisme (Burkina Faso), Institut de Recherche en Sciences de la Santé (Bobo-Dioulasso, Burkina Faso), and Centre National de Formation et de Recherche en Santé Rurale (Republic of Guinea).

Prevalence of the dhfr and dhps Mutations among Pregnant Women in Rural Burkina Faso Five Years after the Introduction of Intermittent Preventive Treatment with Sulfadoxine-Pyrimethamine

BACKGROUND

The emergence and spread of drug resistance represents one of the biggest challenges for malaria control in endemic regions. Sulfadoxine-pyrimethamine (SP) is currently deployed as intermittent preventive treatment in pregnancy (IPTp) to prevent the adverse effects of malaria on the mother and her offspring. Nevertheless, its efficacy is threatened by SP resistance which can be estimated by the prevalence of dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) mutations. This was measured among pregnant women in the health district of Nanoro, Burkina Faso.

METHODS

From June to December 2010, two hundred and fifty six pregnant women in the second and third trimester, attending antenatal care with microscopically confirmed malaria infection were invited to participate, regardless of malaria symptoms. A blood sample was collected on filter paper and analyzed by PCR-RFLP for the alleles 51, 59, 108, 164 in the pfdhfr gene and 437, 540 in the pfdhps gene.

RESULTS

The genes were successfully genotyped in all but one sample (99.6%; 255/256) for dhfr and in 90.2% (231/256) for dhps. The dhfr C59R and S108N mutations were the most common, with a prevalence of 61.2% (156/255) and 55.7% (142/255), respectively; 12.2% (31/255) samples had also the dhfr N51I mutation while the I164L mutation was absent. The dhps A437G mutation was found in 34.2% (79/231) isolates, but none of them carried the codon K540E. The prevalence of the dhfr double mutations NRNI and the triple mutations IRNI was 35.7% (91/255) and 11.4% (29/255), respectively.

CONCLUSION

Though the mutations in the pfdhfr and pfdhps genes were relatively common, the prevalence of the triple pfdhfr mutation was very low, indicating that SP as IPTp is still efficacious in Burkina Faso.

Effectiveness and safety of artemether-lumefantrine versus artesunate-amodiaquine for unsupervised treatment of uncomplicated falciparum malaria in patients of all age groups in Nanoro, Burkina Faso: a randomized open label trial

Background

Several studies have reported high efficacy and safety of artemisinin-based combination therapy (ACT) mostly under strict supervision of drug intake and limited to children less than 5 years of age. Patients over 5 years of age are usually not involved in such studies. Thus, the findings do not fully reflect the reality in the field. This study aimed to assess the effectiveness and safety of ACT in routine treatment of uncomplicated malaria among patients of all age groups in Nanoro, Burkina Faso.

Methods

A randomized open label trial comparing artesunate–amodiaquine (ASAQ) and artemether–lumefantrine (AL) was carried out from September 2010 to October 2012 at two primary health centres (Nanoro and Nazoanga) of Nanoro health district. A total of 680 patients were randomized to receive either ASAQ or AL without any distinction by age. Drug intake was not supervised as pertains in routine practice in the field. Patients or their parents/guardians were advised on the time and mode of administration for the 3 days treatment unobserved at home. Follow-up visits were performed on days 3, 7, 14, 21, and 28 to evaluate clinical and parasitological resolution of their malaria episode as well as adverse events. PCR genotyping of merozoite surface proteins 1 and 2 (msp-1, msp-2) was used to differentiate recrudescence and new infection.

Results

By day 28, the PCR corrected adequate clinical and parasitological response was 84.1 and 77.8 % respectively for ASAQ and AL. The cure rate was higher in older patients than in children under 5 years old. The risk of re-infection by day 28 was higher in AL treated patients compared with those receiving ASAQ (p < 0.00001). Both AL and ASAQ treatments were well tolerated.

Conclusion

This study shows a lowering of the efficacy when drug intake is not directly supervised. This is worrying as both rates are lower than the critical threshold of 90 % required by the WHO to recommend the use of an anti-malarial drug in a treatment policy.

Trial registration: NCT01232530

Ex vivo anti-malarial drug susceptibility of Plasmodium falciparum isolates from pregnant women in an area of highly seasonal transmission in Burkina Faso

Background

Ex vivo assays are usually carried out on parasite isolates collected from patients with uncomplicated Plasmodium falciparum malaria, from which pregnant women are usually excluded as they are often asymptomatic and with relatively low parasite densities. Nevertheless, P. falciparum parasites infecting pregnant women selectively sequester in the placenta and may have a different drug sensitivity profile compared to those infecting other patients. The drug sensitivity profile of P. falciparum isolates from infected pregnant women recruited in a treatment efficacy trial conducted in Burkina Faso was determined in an ex vivo study.

Methods

The study was conducted between October 2010 and December 2012. Plasmodium falciparum isolates were collected before treatment and at the time of any recurrent infection whose parasite density was at least 100/µl. A histidine-rich protein-2 assay was used to assess their susceptibility to a panel of seven anti-malarial drugs. The concentration of anti-malarial drug inhibiting 50% of the parasite maturation to schizonts (IC₅₀) for each drug was determined with the IC Estimator version 1.2.

Results

The prevalence of resistant isolates was 23.5% for chloroquine, 9.2% for mefloquine, 8.0% for monodesethylamodiaquine, and 4.4% for quinine. Dihydroartemisinin, mefloquine, lumefantrine, and monodesethylamodiaquine had the lowest mean IC₅₀ ranging between 1.1 and 1.5 nM respectively. The geometric mean IC₅₀ of the tested drugs did not differ between chloroquine-sensitive and resistant parasites, with the exception of quinine, for which the IC₅₀ was higher for chloroquine-resistant isolates. The pairwise comparison between the IC₅₀ of the tested drugs showed a positive and significant correlation between dihydroartemisinin and both mefloquine and chloroquine, between chloroquine and lumefantrine and between monodesethylamodiaquine and mefloquine.

Conclusion

These ex vivo results suggest that treatment with the currently available artemisinin-based combinations is efficacious for the treatment of malaria in pregnancy in Burkina Faso.

Trial registration

ClinicalTrials.gov ID: NCT00852423

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0769-1) contains supplementary material, which is available to authorized users.

Dynamic of plasmodium falciparum chloroquine resistance transporter gene Pfcrt K76T mutation five years after withdrawal of chloroquine in Burkina Faso

We investigated the evolution of Pfcrt K76T mutation five years after the withdrawal of chloroquine in Burkina Faso. A total of 675 clinical isolates collected from October 2010 to September 2012 were successfully genotyped. Single nucleotide polymorphism in Pfcrt (codon 76) gene was analyzed. The prevalence of resistant Pfcrt 76T allele was 20.55%. There was a progressive decrease of the proportion of mutant type pfcrt T76 from 2010 to 2012 (X2=5.508 p=0.0189). Our results suggest a progressive return of the wild type Pfcrt K76 in Burkina Faso but the prevalence of the mutants Pfcrt T76 still remains high.

Clinical signs and symptoms cannot reliably predict Plasmodium falciparum malaria infection in pregnant women living in an area of high seasonal transmission

Background

Malaria in pregnancy is a major public health problem in endemic countries. Though the signs and symptoms of malaria among pregnant women have been already described, clinical presentation may vary according to intensity of transmission and local perceptions. Therefore, determining common signs and symptoms among pregnant women with a malaria infection may be extremely useful to identify those in need of further investigation by rapid diagnostic test or microscopy.

Methods

Six hundred pregnant women attending the maternity clinic of Nanoro District Hospital, Burkina Faso were recruited, 200 with suspected clinical malaria and 400 as controls. Cases were matched with controls by gestational age and parity. Signs and symptoms were collected and a blood sample taken for rapid diagnostic test, microscopy and haemoglobin measurement. A multivariate model was used to assess the predictive value of signs and symptoms for malaria infection.

Results

The overall prevalence of malaria was 42.6% (256/600) while anaemia was found in 60.8% (365/600) of the women. Nearly half (49%) of the cases and 39.5% of the controls had a malaria infection (p = 0.03). The most common signs and symptoms among the cases were fever (36%,72/200), history of fever (29%,58/200) and headache (52%,104/200). The positive predictive value for fever was 53% (95% CI:41–64), history of fever 58% (95% CI:37–63) and headache 51% (95% CI:41–61).

Conclusion

Signs and symptoms suggestive of malaria are frequent among pregnant women living in areas of intense transmission. Common malaria symptoms are not strong predictors of infection. For a better management of malaria in pregnancy, active screening to detect and treat malaria infection early should be performed on all pregnant women attending a health facility.

Multiple populations of artemisinin-resistant Plasmodium falciparum in Cambodia

We describe an analysis of genome variation in 825 P. falciparum samples from Asia and Africa that identifies an unusual pattern of parasite population structure at the epicenter of artemisinin resistance in western Cambodia. Within this relatively small geographic area, we have discovered several distinct but apparently sympatric parasite subpopulations with extremely high levels of genetic differentiation. Of particular interest are three subpopulations, all associated with clinical resistance to artemisinin, which have skewed allele frequency spectra and high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalog of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in transporter proteins and DNA mismatch repair proteins. These data provide a population-level genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist in its elimination.

VarB: a variation browsing and analysis tool for variants derived from next-generation sequencing data

Summary: There is an immediate need for tools to both analyse and visualize in real-time single-nucleotide polymorphisms, insertions and deletions, and other structural variants from new sequence file formats. We have developed VarB software that can be used to visualize variant call format files in real time, as well as identify regions under balancing selection and informative markers to differentiate user-defined groups (e.g. populations). We demonstrate its utility using sequence data from 50 Plasmodium falciparum isolates comprising two different continents and confirm known signals from genomic regions that contain important antigenic and anti-malarial drug-resistance genes.

Availability and implementation: The C++-based software VarB and user manual are available from www.pathogenseq.org/varb.

Contact:taane.clark@lshtm.ac.uk

Analysis of Plasmodium falciparum diversity in natural infections by deep sequencing

Malaria elimination strategies require surveillance of the parasite population for genetic changes that demand a public health response, such as new forms of drug resistance. Here we describe methods for the large-scale analysis of genetic variation in Plasmodium falciparum by deep sequencing of parasite DNA obtained from the blood of patients with malaria, either directly or after short-term culture. Analysis of 86,158 exonic single nucleotide polymorphisms that passed genotyping quality control in 227 samples from Africa, Asia and Oceania provides genome-wide estimates of allele frequency distribution, population structure and linkage disequilibrium. By comparing the genetic diversity of individual infections with that of the local parasite population, we derive a metric of within-host diversity that is related to the level of inbreeding in the population. An open-access web application has been established for the exploration of regional differences in allele frequency and of highly differentiated loci in the P. falciparum genome.

An analysis of timing and frequency of malaria infection during pregnancy in relation to the risk of low birth weight, anaemia and perinatal mortality in Burkina Faso

BACKGROUND

A prospective study aiming at assessing the effect of adding a third dose sulphadoxine-pyrimethamine (SP) to the standard two-dose intermittent preventive treatment for pregnant women was carried out in Hounde, Burkina Faso, between March 2006 and July 2008. Pregnant women were identified as earlier as possible during pregnancy through a network of home visitors, referred to the health facilities for inclusion and followed up until delivery.

METHODS

Study participants were enrolled at antenatal care (ANC) visits and randomized to receive either two or three doses of SP at the appropriate time. Women were visited daily and a blood slide was collected when there was fever (body temperature > 37.5°C) or history of fever. Women were encouraged to attend ANC and deliver in the health centre, where the new-born was examined and weighed. The timing and frequency of malaria infection was analysed in relation to the risk of low birth weight, maternal anaemia and perinatal mortality.

RESULTS

Data on birth weight and haemoglobin were available for 1,034 women. The incidence of malaria infections was significantly lower in women having received three instead of two doses of SP. Occurrence of first malaria infection during the first or second trimester was associated with a higher risk of low birth weight: incidence rate ratios of 3.56 (p < 0.001) and 1.72 (p = 0.034), respectively. After adjusting for possible confounding factors, the risk remained significantly higher for the infection in the first trimester of pregnancy (adjusted incidence rate ratio = 2.07, p = 0.002). The risk of maternal anaemia and perinatal mortality was not associated with the timing of first malaria infection.

CONCLUSION

Malaria infection during first trimester of pregnancy is associated to a higher risk of low birth weight. Women should be encouraged to use long-lasting insecticidal nets before and throughout their pregnancy.

Approche socio-anthropologique de la dynamisation du réseau d'acteurs de prise en charge des malades tuberculeux au Burkina Faso

La tuberculose est une maladie chronique dont la prise en charge nécessite une approche multisectorielle: le social et le biomédical. Une étude socio-anthropologique retraçant les itinéraires thérapeutiques des malades a permis d'identifier les détenteurs d'enjeux dans la gestion de la maladie pour élaborer une « carte des acteurs » et encourager une interaction dynamique entre les membres. L'identification des acteurs clés et leur mise en réseau a permis d'entreprendre des actions contribuant à renforcer l'efficacité et l'efficience de la prise en charge des malades au Burkina Faso, par des actions collectives. Nous identifions ainsi des acteurs sociaux, alliés et confidents des malades; des acteurs biomédicaux, directement concernés par la prise en charge médicale de la maladie. A travers ces liens entre les acteurs, nous remarquons que les systèmes de santé sont caractérisés par des interactions sur fond d'incompréhension qui influence négativement la qualité des soins. La dynamisation du réseau d'acteurs a permis d'éprouver un mode de collaboration axé sur l'analyse collective des problèmes rencontrés par les prestataires de soins et les malades tuberculeux. Celle-ci a permis la mise en œuvre d'actions visant à améliorer la qualité de vie des malades. La dynamique de collaboration entre acteurs concernés par l'accès aux soins de santé a eu raison sur les situations problématiques qui entament les succès thérapeutiques et la qualité de vie des malades tuberculeux. (Global Health Promotion, 2009; 16 (1): pp. 72—80)

Newcastle disease virus in West Africa: new virulent strains identified in non-commercial farms

Forty-four Newcastle disease virus (NDV) strains, obtained between 2002 and 2007 from different poultry species in Nigeria, Niger, Burkina Faso and Cameroon, were phylogenetically analysed based on partial F sequences. Lineage 2 viruses were genetically identical or similar to the locally used LaSota vaccine strain and were mostly detected in commercial farms. Lineage 1, 3 and 4 strains were only sporadically found, and their origin was less clear. Twenty-one strains from backyard farms and live bird markets formed three new clusters within lineage 5, tentatively named 5f, 5g and 5h. All of these strains were predicted to be virulent based on their F protein cleavage site sequence. Minimal genetic distances between new and previously established sublineages ranged from 9.4 to 15.9%, and minimal distances between the new sublineages were 11.5 to 17.3%. Their high genetic diversity and their presence in three different Sub-Saharan countries suggest that these new sublineages represent the NDV variants indigenous to West Africa.

Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial

Background

Vitamin A and zinc are crucial for normal immune function, and may play a synergistic role for reducing the risk of infection including malaria caused by Plasmodium falciparum.

Methods

A randomized, double-blind, placebo-controlled trial of a single dose of 200 000 IU of vitamin A with daily zinc supplementation was done in children of Sourkoudougou village, Burkina Faso. Children aged from 6 to 72 months were randomized to receive a single dose of 200 000 IU of vitamin A plus 10 mg elemental zinc, six days a week (n = 74) or placebo (n = 74) for a period of six months. Cross-sectional surveys were conducted at the beginning and the end of the study, and children were evaluated daily for fever. Microscopic examination of blood smear was done in the case of fever (temperature ≥37.5°C) for malaria parasite detection.

Results

At the end of the study we observed a significant decrease in the prevalence malaria in the supplemented group (34%) compared to the placebo group (3.5%) (p < 0.001). Malaria episodes were lower in the supplemented group (p = 0.029), with a 30.2% reduction of malaria cases (p = 0.025). Time to first malaria episode was longer in the supplemented group (p = 0.015). The supplemented group also had 22% fewer fever episodes than the placebo group (p = 0.030).

Conclusion

These results suggest that combined vitamin A plus zinc supplementation reduces the risk of fever and clinical malaria episodes among children, and thus may play a key role in malaria control strategies for children in Africa.

Molecular and antigenic evolution and geographical spread of H5N1 highly pathogenic avian influenza viruses in western Africa

In Africa, highly pathogenic avian influenza H5N1 virus was first detected in northern Nigeria and later also in other regions of the country. Since then, seven other African countries have reported H5N1 infections. This study reports a comparison of full-length genomic sequences of H5N1 isolates from seven chicken farms in Nigeria and chicken and hooded vultures in Burkina Faso with earlier H5N1 outbreaks worldwide. In addition, the antigenicity of Nigerian H5N1 isolates was compared with earlier strains. All African strains clustered within three sublineages denominated A (south-west Nigeria, Niger), B (south-west Nigeria, Egypt, Djibouti) and C (northern Nigeria, Burkina Faso, Sudan, Côte d'Ivoire), with distinct nucleotide and amino acid signatures and distinct geographical distributions within Africa. Probable non-African ancestors within the west Asian/Russian/European lineage distinct from the south-east Asian lineages were identified for each sublineage. All reported human cases in Africa were caused by sublineage B. Substitution rates were calculated on the basis of sequences from 11 strains from a single farm in south-west Nigeria. As H5N1 emerged essentially at the same time in the north and south-west of Nigeria, the substitution rates confirmed that the virus probably did not spread from the north to the south, given the observed sequence diversity, but that it entered the country via three independent introductions. The strains from Burkina Faso seemed to originate from northern Nigeria. At least two of the sublineages also circulated in Europe in 2006 as seen in Germany, further suggesting that the sublineages had already emerged outside of Africa and seemed to have followed the east African/west Asian and Black Sea/Mediterranean flyways of migratory birds.

[An action research network to improve the quality of tuberculosis care in West Africa]

BACKGROUND

Improvement in management systems for tuberculosis (TB) care is urgently needed in West Africa. In 2003, an experimental action research network began there, involving care providers, health system managers, and TB programme managers. Each project in all 6 countries used a "patient-centered" approach to improve tuberculosis case management.

METHODS

The research teams included care providers, district medical officers, anthropologists and TB programme managers. Each research team conducted its project for a one-year period and then assessed its results. The specific problems identified were low TB detection rates (Burkina Faso, Côte d'Ivoire and Niger) and poor compliance among patients receiving treatment, including their ensuing loss to follow-up (Benin, Mali and Senegal). Investigators concluded that these weaknesses were due to the lack of access to care (geographical, financial and cultural), the complexity of the care system and the low quality of care. Solutions for all 6 countries aimed at improving access to high-quality care.

RESULTS

One year after the experiment began, results varied from one country to another. In general, all participants understood the need to collaborate beyond national health systems because the problems from all 6 countries were quite similar. The research process led to better sharing of work between care providers and sometimes between care providers and TB patients. It provided participants with new concepts and a constant opportunity to implement them. These repeated meetings, however, keep care providers away from their offices.

CONCLUSION

The research would have improved case management and care more effectively had the teams taken into account the psychological and sociological need of TB patients. A new regional dynamic has begun and must be pursued to help improve health care systems.

Roles of specific Plasmodium falciparum mutations in resistance to amodiaquine and sulfadoxine-pyrimethamine in Burkina Faso

We evaluated associations between key polymorphisms in target genes and responses to treatment with sulfadoxine-pyrimethamine (SP) or amodiaquine (AQ) for uncomplicated Plasmodium falciparum malaria in Bobo-Dioulasso, Burkina Faso. Presence of the dihydrofolate reductase (dhfr) 108N or 59R mutations (but not dhfr 51I or dihydropteroate synthetase [dhps] 437G) and P. falciparum chloroquine resistance transporter (pfcrt) 76T or P. falciparum multidrug resistance 1 (pfmdr1) 86Y or 1246Y mutations (but not pfmdr1 184F) predicted recrudescence after treatment with SP and AQ, respectively. Treatment led to significant increases in the prevalence of the same mutations (except 1246Y) in new infections that presented after therapy. The dhfr 164L and dhps 540E mutations were not seen in any isolates. These results clarify the key roles of a small number of mutations in P. falciparum resistance to SP and AQ in west Africa.

Decentralising tuberculosis case management in two districts of Burkina Faso

SETTING

In West Africa, national tuberculosis programmes (NTPs) face many problems due to the low performance of health care delivery systems and patients' social and cultural environment.

OBJECTIVE

To improve the case management of TB in Burkina Faso.

DESIGN

Using the operational research process as a tool, TB case management was decentralised from the district hospital to eight primary health care centres in 2003.

RESULTS

Twelve months after decentralisation, the quality of case detection remained satisfactory. The delay between the identification of TB suspects with chronic cough and the confirmation of TB was reduced from 13 to 6 days. The detection rate of TB suspects during the study (30%) was twice as high as for 2001 and 2002 (15%). However, the detection rate for smear-positive TB cases decreased from 32.3% in 2001 and 2002 to 6.5% during the year of the study.

CONCLUSION

Sufficient time and commitment are essential to obtain a case management system that is decentralised and effective. Efforts therefore need to continue to obtain more information and better results.

Amodiaquine, sulfadoxine-pyrimethamine, and combination therapy for uncomplicated falciparum malaria: a randomized controlled trial from Burkina Faso

Increasing resistance to chloroquine necessitates the evaluation of other antimalarial therapies in Africa. We compared the efficacies of amodiaquine (AQ), sulfadoxine-pyrimethamine (SP), and AQ + SP for the treatment of uncomplicated falciparum malaria in a randomized trial of patients 6 months of age or older in Bobo-Dioulasso, Burkina Faso. Of the 944 patients enrolled, 829 (88%; 53% under 5 years of age) were assigned 28-day efficacy outcomes. For all regimens, early treatment failures were uncommon (< 2%). Considering all treatment failures based on WHO criteria, AQ + SP was most efficacious (failures in 4.2%), followed by SP (9.1%) and AQ (17.9%; P < 0.02 for all pairwise comparisons). Considering only clinical failures, relative efficacies were similar (failures in 2.1% with AQ + SP, 6.5% with SP, and 13.2% with AQ; P < 0.02 for all pairwise comparisons). The risk of recrudescence was lower with AQ + SP (2.1%) compared with SP (6.1%, P = 0.02) and AQ (8.1%, P = 0.001). Risks of new infection were lower with AQ + SP (2.1%) and SP (2.4%) compared with AQ (9.1%, P < 0.001 for both comparisons). No serious adverse events were seen. AQ + SP appears to offer a highly effective, inexpensive, and available therapy for the treatment of uncomplicated malaria in Burkina Faso.

First report of a kdr mutation in Anopheles arabiensis from Burkina Faso, West Africa

The leu-phe kdr mutation was detected in a specimen of Anopheles arabiensis during an extensive survey of pyrethroid resistance in An. gambiae s.l. in Burkina Faso. The detection of this mutation in An. arabiensis, which had so far been observed only in An. gambiae s.s., is important at both epidemiologic and fundamental levels. It can be useful to understand the history of this gene throughout the range of An. gambiae complex.

Natural swarming behaviour of the molecular M form of Anopheles gambiae

In Anopheles gambiae, as in most species of mosquitoes, mating is initiated in flight. The males aggregate in aerial swarms and conspecific females individually fly to these swarms where they mate with males. In this study, we investigated the swarming behaviour of A. gambiae and conducted 2 surveys in the rice field area of the Vallée du Kou in Burkina Faso in 1999 and 2002. A high number of anopheline mosquitoes were observed in this area and both molecular M and S forms of A. gambiae were found in sympatry. Swarms formed a few minutes after sunset in different places and no obvious markers were associated with their occurrence. However, swarms occurred close to cow herds generally in open flat areas, 2-3 m above the ground. Overall, 2829 anopheline mosquitoes were collected from 21 swarms composed primarily of males. A few specimens of Culex quinquefasciatus were collected from 3 swarms. Although both molecular M and S forms were found in sympatry in the village, swarms were composed almost exclusively of the molecular M form. This suggests that there are alternative swarming habits for both molecular M and S forms of A. gambiae in nature.

Chloroquine and sulphadoxine-pyrimethamine efficacy for uncomplicated malaria treatment and haematological recovery in children in Bobo-Dioulasso, Burkina Faso during a 3-year period 1998-2000

We determined the parasitological resistance and the clinical failure to chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) by the WHO 14-day in vivo test over three consecutive years in 948 children aged 6-59 months with uncomplicated malaria attending four health centres in the province of Houet, Burkina Faso. Children were alternatively allocated to either CQ or SP. Packed cell volume (PCV) was measured at days 0 and 14. Parasitological resistance (RI, RII and RIII) to CQ was 18% (83 of 455) and to SP <1% (two of 308). Clinical failure with CQ was 12% (53 of 455) with no evidence of increase over time. Only one case of clinical failure was detected among the children treated with SP. The prevalence of anaemia (PCV <25%) was about 40% at day 0 and had decreased substantially by day 14 in both groups. However, in children treated with SP the prevalence of anaemia at day 14 was significantly lower than in those treated with CQ:RR = 3.15 (95% CI: 1.33-7.42, P = 0.008). CQ and SP are still efficacious for the treatment of uncomplicated malaria in children, at least in this area of Burkina Faso. However, the prevalences of CQ resistance reported from other areas of the country are worrying because of its potential spread. Regular surveillance of resistance to commonly used antimalarial drugs should continue.

[In vitro susceptibility of 232 isolates of Plasmodium falciparum to antimalarials in Burkina Faso (West Africa)]

Plasmodium falciparum in vitro susceptibility to chloroquine, quinine, mefloquine and halofantrine was investigated in patients living in Bobo-Dioulasso (Burkina Faso, West Africa). Our study was carried out from July to November 1997 at the Malaria Chemoresistance Reference Centre, Centre MurazIOCCGE. Inclusion criteria were: presence of a single infection by R falciparum with a parasite count > or =4000 infected red cells/mm3. The susceptibility to drugs was measured after an incubation period of 48 hours at 37 degrees C, under 5% CO2. (3H) Hypoxanthine was added to the medium to monitor parasite growth. 134 isolates of P. falciparum were tested against chloroquine; 24.6% (33/134) were resistant. We have also documented 11.2% (15/133) of resistant isolates to halofantrine. All the tested isolates were susceptible to quinine (n=135) and mefloquine (n=136). A significant positive correlation was found between the following IC50 values: chloroquine-quinine, quinine-mefloquine and mefloquine-halofantrine. Our study shows no significant increase of the prevalence of chloroquine-resistant strains of P. falciparum in our study area; as well as the persistence of resistance to halofantrine with regard to previous publications in the subject.

[Preliminary study of cutaneous leishmaniasis in the town of Ouagadougou from 1996 to 1998]

Since 1996, there have been reports of cases of cutaneous leishmaniasis in the town of Ouagadougou. The incidence has been on the rise but precise figures are not known. The object of the present study has been, first, to record cases of cutaneous leishmaniasis having occurred in private and public health centres in Ouagadougou from 1996 to 1998 and, second, to determine the progression of the disease in space and time. We wished also to confirm clinical cases in 1998 by parasitological examination, identify different clinical forms of the disease and map out cases in the town. We carried out a retrospective study from 1996 to 1998 and a prospective study in 1998. All cases recorded in this period in visited health centres were included. A total of 1845 cases of cutaneous leishmaniasis was identified, 50.3% of whom concerned women. The age of patients varied between 1 and 79 years for 356 patients, with a mean age of 26.7 years. Cases increased between 1996 and 1998 (1996 = 61 cases, 1997 = 552 cases, 1998 = 1218 cases). The months of highest incidence were August (13%), September (15%) and October (17%). Peripheral districts (28, 30, 29, 16, 15) in south-eastern areas of the town were the worst touched with 87% of cases. On average, patients seek care after 2 months of progression of the disease. The ulcero-crusted form (68.2%) was the most frequent clinical form observed for 327 patients, but almost half of the cases had more than one site of infection, (43.5%). Over half of the patients presented fewer than 10 lesions with an average of 6. The most common locations were on uncovered parts of the body, notably the superior (53%) and inferior limbs (49%). The parasite could be tested for by smear on 52 patients only in 1998 and 53.8% of cases tested were positive. Leishmania major, which is very prevalent in West Africa was identified in one patient. The vectors and main reservoirs of the parasite were not studied. Case management was generally incomplete; the most commonly prescribed drugs were antibiotics (70% of patients), but self-medication was frequent. Our recommendations after this preliminary study are: undertake multidisciplinary studies on cutaneous leishmaniasis in Ouagadougou in order to understand the local aetiology (vectors responsible for transmission, rodent and domestic animals involved in the epidemiological chain, parasite species); identify all other areas in the country where the disease is highly prevalent provide health care staff with a decisional algorithm and protocol therapy carry out and active control programme for cutaneous leishmaniasis in Burkina Faso.

[Malaria morbidity in adults living in urban Burkina Faso]

Urbanization in countries located in areas of endemic malaria can decrease the level of immunization and make malaria a more serious public health problem in adults. The purpose of this prospective study was to describe the clinical and parasitological features of malaria in adults in the city of Bobo Dioulasso in Burkina Faso. Study was carried out between July and November 1992 at the medical testing laboratory of the Muraz Center in 494 patients including 378 adults and 116 children under the age of 15 years. The parasitic index was 23% in adults as compared to 62% in children. There was not a significant difference in the parasitic index according to whether the place of residence was located in the city center or outlying suburbs. Parasite density ranged from 6 to 145,000 parasites per mm3 in adults as compared to 6 to 426,000 parasites per mm3 in children. Median parasitemia was 696 parasites per mm3 in adults as compared to 8800 per mm3 in children. The threshold of parasitemia for appearance of clinical symptoms was thus lower in adults than in children. Because of the poor positive predictive value of the main clinical features and the high incidence of self-treatment, microscopic examination is indispensable to confirm diagnosis of malaria. The results of this study indicate that urbanization in the city of Bobo Dioulasso has not significantly changed the level of immunization to malaria in adults.