Mosquitocidal effect of ivermectin-treated nettings and sprayed walls on Anopheles gambiae s.s.

Ivermectin (IVM) has been proposed as a new tool for malaria control as it is toxic on vectors feeding on treated humans or cattle. Nevertheless, IVM may have a direct mosquitocidal effect when applied on bed nets or sprayed walls. The potential for IVM application as a new insecticide for long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) was tested in this proof-of-concept study in a laboratory and semi-field environment. Laboratory-reared, insecticide-susceptible Kisumu Anopheles gambiae were exposed to IVM on impregnated netting materials and sprayed plastered- and mud walls using cone bioassays. The results showed a direct mosquitocidal effect of IVM on this mosquito strain as all mosquitoes died by 24 h after exposure to IVM. The effect was slower on the IVM-sprayed walls compared to the treated nettings. Further work to evaluate possibility of IVM as a new insecticide formulation in LLINs and IRS will be required.

Household-level effects of seasonal malaria chemoprevention in the Gambia.

BACKGROUND: In 2022 the WHO recommended the discretionary expansion of the eligible age range for seasonal malaria chemoprevention (SMC) to children older than 4 years. Older children are at lower risk of clinical disease and severe malaria so there has been uncertainty about the cost-benefit for national control programmes. However, emerging evidence from laboratory studies suggests protecting school-age children reduces the infectious reservoir for malaria and may significantly impact on transmission. This study aimed to assess whether these effects were detectable in the context of a routinely delivered SMC programme. METHODS: In 2021 the Gambia extended the maximum eligible age for SMC from 4 to 9 years. We conducted a prospective population cohort study over the 2021 malaria transmission season covering 2210 inhabitants of 10 communities in the Upper River Region, and used a household-level mixed modelling approach to quantify impacts of SMC on malaria transmission. RESULTS: We demonstrate that the hazard of clinical malaria in older participants aged 10+ years ineligible for SMC decreases by 20% for each additional SMC round per child 0-9 years in the same household. Older inhabitants also benefit from reduced risk of asymptomatic infections in high SMC coverage households. Spatial autoregression tests show impacts are highly localised, with no detectable spillover from nearby households. CONCLUSIONS: Evidence for the transmission-reducing effects of extended-age SMC from routine programmes implemented at scale has been previously limited. Here we demonstrate benefits to the entire household, indicating such programmes may be more cost-effective than previously estimated.

Seasonal malaria chemoprevention (SMC) is the provision of monthly, preventative, anti-malaria medication to young children at times when they are most at risk of severe disease. Recently the World Health Organisation recommended expanding SMC to children older than 4 years. Older children with malaria typically remain symptomless so the advantages were unclear. However, laboratory evidence suggests this group continues to transmit malaria to others. We conducted a population study in 2021 in 10 communities in the Gambia where SMC was extended to all children up to 9 years of age for the first time. We found household members aged over 9 years were less likely to get clinical disease when most young children in the same household did receive SMC. This suggests an added protection of SMC for those who do not receive it, potentially increasing cost-effectiveness.

Efficacy and safety of pyronaridine-artesunate (PYRAMAX) for the treatment of P. falciparum uncomplicated malaria in African pregnant women (PYRAPREG): study protocol for a phase 3, non-inferiority, randomised open-label clinical trial.

INTRODUCTION: Malaria infection during pregnancy increases the risk of low birth weight and infant mortality and should be prevented and treated. Artemisinin-based combination treatments are generally well tolerated, safe and effective; the most used being artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP). Pyronaridine-artesunate (PA) is a new artemisinin-based combination. The main objective of this study is to determine the efficacy and safety of PA versus AL or DP when administered to pregnant women with confirmed Plasmodium falciparum infection in the second or third trimester. The primary hypothesis is the pairwise non-inferiority of PA as compared with either AL or DP. METHODS AND ANALYSIS: A phase 3, non-inferiority, randomised, open-label clinical trial to determine the safety and efficacy of AL, DP and PA in pregnant women with malaria in five sub-Saharan, malaria-endemic countries (Burkina Faso, Democratic Republic of the Congo, Mali, Mozambique and the Gambia). A total of 1875 pregnant women will be randomised to one of the treatment arms. Women will be actively monitored until Day 63 post-treatment, at delivery and 4-6 weeks after delivery, and infants' health will be checked on their first birthday. The primary endpoint is the PCR-adjusted rate of adequate clinical and parasitological response at Day 42 in the per-protocol population. ETHICS AND DISSEMINATION: This protocol has been approved by the Ethics Committee for Health Research in Burkina Faso, the National Health Ethics Committee in the Democratic Republic of Congo, the Ethics Committee of the Faculty of Medicine and Odontostomatology/Faculty of Pharmacy in Mali, the Gambia Government/MRCG Joint Ethics Committee and the National Bioethics Committee for Health in Mozambique. Written informed consent will be obtained from each individual prior to her participation in the study. The results will be published in peer-reviewed open access journals and presented at (inter)national conferences and meetings. TRIAL REGISTRATION NUMBER: PACTR202011812241529.

Molecular surveillance of Plasmodium falciparum drug-resistance markers in Vietnam using multiplex amplicon sequencing (2000-2016).

Emergence and spread of Plasmodium falciparum resistance to artemisinin-based combination therapies (ACT) is a major challenge for Greater Mekong Subregion countries in their goal to eliminate malaria by 2030. Tools to efficiently monitor drug resistance beyond resource-demanding therapeutic efficacy studies are necessary. A custom multiplex amplicon sequencing assay based on Illumina technology was designed to target the marker of partial resistance to artemisinin (K13), five candidate modulators of artemisinin resistance, the marker of resistance to chloroquine (crt), and four neutral microsatellite loci. The assay was used to genotype 635 P. falciparum-positive blood samples collected across seven provinces of Vietnam and one of Cambodia between 2000 and 2016. Markers of resistance to artemisinin partner-drugs piperaquine (copy number of plasmepsin-2) and mefloquine (copy number of multidrug-resistance 1) were determined by qPCR. Parasite population structure was further assessed using a 101-SNP barcode. Validated mutations of artemisinin partial resistance in K13 were found in 48.1% of samples, first detection was in 2000, and by 2015 prevalence overcame > 50% in Central Highlands and Binh Phuoc province. K13-C580Y variant became predominant country-wide, quickly replacing an outbreak of K13-I543T in Central Highlands. Mutations in candidate artemisinin resistance modulator genes paralleled the trends of K13 mutants, whereas resistance to piperaquine and mefloquine remained low (≈ 10%) by 2015-2016. Genomic tools applied to malaria surveillance generate comprehensive information on dynamics of drug resistance and population structure and reflect drug efficacy profiles from in vivo studies.

Laboratory Evaluation of a SARS-CoV-2 RT-LAMP Test.

There is a need to have more accessible molecular diagnostic tests for the diagnosis of severe acute respiratory syndrome coronavirus 2 disease in low- and middle-income countries. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) may provide an attractive option as this technology does not require a complex infrastructure. In this study, the diagnostic performance of a SARS-CoV-2 RT-LAMP was evaluated using RT-PCR-confirmed clinical specimens of COVID-19-positive (n = 55) and -negative patients (n = 55) from the Netherlands. The observed sensitivity of the RT-LAMP test was 97.2% (95% CI: 82.4-98.0%) and the specificity was 100% (95% CI: 93.5-100%). The positive predictive value of the RT-LAMP was 100%, the negative predictive value 93.2% (95% CI: 84.3-97.3%), and the diagnostic accuracy was 96.4% (95% CI: 91.0-99.0%). The agreement between the RT-LAMP and the RT-PCR was "almost perfect" (κ-value: 0.92). The evaluated RT-LAMP might provide an attractive alternative molecular diagnostic tool for SARS-CoV-2 in resource limited settings.

Perceptions and acceptability of the controlled human malaria infection (CHMI) model in The Gambia: a qualitative study.

Controlled human malaria infection (CHMI) studies, i.e. the deliberate infection of healthy volunteers with malaria parasites to study immune response and/or test drug or vaccine efficacy, are increasingly being conducted in malaria endemic countries, including in sub-Saharan Africa. However, there have been few studies on the perceptions and acceptability of CHMI by the local communities. This qualitative study assessed the perception and acceptability of such studies in The Gambia following the first CHMI study conducted in the country in March-May 2018. Data were collected through non-participant observation, in-depth interviews and focus group discussions and analyzed using NVivo 12 software with an inductive-deductive approach. Sixty-seven participants were involved, including volunteers enrolled in the CHMI, community stakeholders and members of the Gambian Ethics Committee. Respondents expressed a positive view about CHMI. Key motivating factors for participation were the financial compensation, comprehensive health checks, and willingness to support malaria research. Risks associated with participation were considered low. Concerns raised included the frequency of bleeding and the blood volume collected.

Genomic Epidemiology of SARS-CoV-2 in Western Burkina Faso, West Africa.

BACKGROUND: After its initial detection in Wuhan, China, in December 2019, SARS-CoV-2 has spread rapidly, causing successive epidemic waves worldwide. This study aims to provide a genomic epidemiology of SARS-CoV-2 in Burkina Faso. METHODS: Three hundred and seventy-seven SARS-CoV-2 genomes obtained from PCR-positive nasopharyngeal samples (PCR cycle threshold score < 35) collected between 5 May 2020, and 31 January 2022 were analyzed. Genomic sequences were assigned to phylogenetic clades using NextClade and to Pango lineages using pangolin. Phylogenetic and phylogeographic analyses were performed to determine the geographical sources and time of virus introduction in Burkina Faso. RESULTS: The analyzed SARS-CoV-2 genomes can be assigned to 10 phylogenetic clades and 27 Pango lineages already described worldwide. Our analyses revealed the important role of cross-border human mobility in the successive SARS-CoV-2 introductions in Burkina Faso from neighboring countries. CONCLUSIONS: This study provides additional insights into the genomic epidemiology of SARS-CoV-2 in West Africa. It highlights the importance of land travel in the spread of the virus and the need to rapidly implement preventive policies. Regional cross-border collaborations and the adherence of the general population to government policies are key to prevent new epidemic waves.

Entomological impact of mass administration of ivermectin and dihydroartemisinin-piperaquine in The Gambia: a cluster-randomized controlled trial.

BACKGROUND: Vector control interventions in sub-Saharan Africa rely on insecticide-treated nets and indoor residual spraying. Insecticide resistance, poor coverage of interventions, poor quality nets and changes in vector behavior threaten the effectiveness of these interventions and, consequently, alternative tools are needed. Mosquitoes die after feeding on humans or animals treated with ivermectin (IVM). Mass drug administration (MDA) with IVM could reduce vector survival and decrease malaria transmission. The entomological impact of MDA of combined IVM and dihydroartemisinin-piperaquine was assessed in a community-based, cluster-randomized trial. METHODS: A cluster-randomized trial was implemented in 2018 and 2019 in 32 villages in the Upper River Region, The Gambia. The with the inhabitants of 16 intervention villages eligible to receive three monthly rounds of MDA at the beginning of the malaria transmission season. Entomological surveillance with light traps and human landing catches (HLC) was carried out during a 7- to 14-day period after each round of MDA, and then monthly until the end of the year. The mosquitocidal effect of IVM was determined by direct membrane feeding assays. RESULTS: Of the 15,017 mosquitoes collected during the study period, 99.65% (n = 14,965) were Anopheles gambiae sensu lato (An. gambiae s.l.), comprising Anopheles arabiensis (56.2%), Anopheles coluzzii (24.5%), Anopheles gambiae sensu stricto (An. gembiae s.s.; 16.0%) and Anopheles funestus sensu lato (An. funestus s.l.; 0.35%). No effect of the intervention on vector parity was observed. Vector density determined on light trap collections was significantly lower in the intervention villages in 2019 (adjusted incidence rate ratio: 0.39; 95% confidence interval [CI]: 0.20, 0.74; P = 0.005) but not in 2018. However, vector density determined in HLC collections was similar in both the intervention and control villages. The entomological inoculation rate was significantly lower in the intervention villages than in the control villages (odds ratio: 0.36, 95% CI: 0.19, 0.70; P = 0·003). Mosquito mortality was significantly higher when blood fed on IVM-treated individuals up to 21 days post-treatment, particularly in adults and individuals with a higher body mass index. CONCLUSION: Mass drug administration with IVM decreased vector density and the entomological inoculation rate while the effect on vector parity was less clear. Survival of mosquitoes fed on blood collected from IVM-treated individuals was significantly lower than that in mosquitoes which fed on controls. The influence of host characteristics on mosquito survivorship indicated that dose optimization could improve IVM efficacy. Future detailed entomological evaluation trials in which IVM is administered as stand-alone intervention may elucidate the contribution of this drug to the observed reduction in transmission.

Why using bed nets is a challenge among minority populations in Central Vietnam.

BACKGROUND: Despite freely distributed insecticide-treated nets (ITNs) and health information campaigns to increase their use among populations at risk, malaria transmission persists in forested areas in Vietnam, especially among ethnic minority communities. A mixed-methods study was conducted in four villages of Ca Dong and M'nong ethnicity in Central Vietnam between 2009 and 2011 to assess factors limiting the uptake of ITNs. METHODS: The mixed-methods research design consisted of a qualitative study to explore the context and barriers to ITN use, and a cross-sectional household survey (n = 141) to quantify factors for limited and appropriate net use. RESULTS: The Ca Dong and M'nong's livelihood was dependent on swidden farming in the forest. Poverty-related factors, including the lack of beds, blankets, the practice of sleeping around the kitchen fire and deteriorated ITNs due to open housing structures, were reasons for alternative and non-use of ITNs. When household members stayed overnight in plot huts at fields, ITNs were even more unavailable and easily deteriorated. 72.5% of households reported having received one net for every two persons, and 82.2% of participants reported to have used ITNs the night before the survey. However, only 18.4% of participants were estimated to be effectively protected by ITNs after accounting for the availability of torn ITNs and the way ITNs were used, for example as blankets, at both village and fields. Multi-variable logistic regression showed the effect of four significant factors for appropriate ITN use: i) being female (AOR = 8.08; p = 0.009); ii) aware of mosquito bites as the sole cause of malaria (AOR = 7.43; p = 0.008); iii) not sleeping around the kitchen fire (AOR = 24.57; p = 0.001); and iv) having sufficient number of ITNs in the household (AOR = 21.69; p = 0.001). CONCLUSION: This study showed how social factors rooted in poverty and swidden agriculture limited the effective use of ITNs, despite high coverage, among ethnic minority populations in Central Vietnam. An in-depth understanding of the local context is essential to develop specific indicators for measuring ITN use.

Rheumatic heart disease in The Gambia: clinical and valvular aspects at presentation and evolution under penicillin prophylaxis.

BACKGROUND: Rheumatic heart disease (RHD) remains the leading cause of cardiac-related deaths and disability in children and young adults worldwide. In The Gambia, the RHD burden is thought to be high although no data are available and no control programme is yet implemented. We conducted a pilot study to generate baseline data on the clinical and valvular characteristics of RHD patients at first presentation, adherence to penicillin prophylaxis and the evolution of lesions over time. METHODS: All patients registered with acute rheumatic fever (ARF) or RHD at two Gambian referral hospitals were invited for a clinical review that included echocardiography. In addition, patients were interviewed about potential risk factors, disease history, and treatment adherence. All clinical and echocardiography information at first presentation and during follow-up was retrieved from medical records. RESULTS: Among 255 registered RHD patients, 35 had died, 127 were examined, and 111 confirmed RHD patients were enrolled, 64% of them females. The case fatality rate in 2017 was estimated at 19.6%. At first presentation, median age was 13 years (IQR [9; 18]), 57% patients had late stage heart failure, and 84.1% a pathological heart murmur. Although 53.2% of them reported history of recurrent sore throat, only 32.2% of them had sought medical treatment. A history suggestive of ARF was reported by 48.7% patients out of whom only 15.8% were adequately treated. Two third of the patients (65.5%) to whom it was prescribed were fully adherent to penicillin prophylaxis. Progressive worsening and repeated hospitalisation was experienced by 46.8% of the patients. 17 patients had cardiac surgery, but they represented only 18.1% of the 94 patients estimated eligible for cardiac surgery. CONCLUSION: This study highlights for the first time in The Gambia the devastating consequences of RHD on the health of adolescents and young adults. Our findings suggest a high burden of disease that remains largely undetected and without appropriate secondary prophylaxis. There is a need for the urgent implementation of an effective national RHD control programto decrease the unacceptably high mortality rate, improve case detection and management, and increase community awareness of this disease.

High Proportion of Genome-Wide Homology and Increased Pretreatment pvcrt Levels in Plasmodium vivax Late Recurrences: a Chloroquine Therapeutic Efficacy Study.

Chloroquine (CQ) is the first-line treatment for Plasmodium vivax malaria in most countries where malaria is endemic. Monitoring P. vivax CQ resistance (CQR) is critical but remains challenged by the difficulty to distinguish real treatment failure from reinfection or liver relapse. The therapeutic efficacy of CQ against uncomplicated P. vivax malaria was evaluated in Gia Lai Province, Vietnam. Sixty-seven patients were enrolled and followed for 42 days using microscopy and quantitative PCR. Adequate clinical and parasitological response (ACPR) was 100% (66/66) on day 28 but 75.4% (49/65) on day 42. Eighteen recurrences (27.7%) were detected, with a median time to recurrence of 42 days (interquartile range [IQR], 35 to 42) and blood CQ concentration of <100 ng/ml. Primary infections leading to recurrence occurred in younger individuals (median age for ACPR = 25 years [IQR, 20 to 28]; recurrences = 18 [16 to 21]; P = 0.002) had a longer parasite clearance time (PCT for ACPR = 47.5 h [IQR, 36.2 to 59.8 h]; recurrences = 54.2 [48.4 to 62.0]; P = 0.035) and higher pvcrt gene expression (median relative expression ratio for ACPR = 0.09 [IQR, 0.05 to 0.22]; recurrences = 0.20 [0.15 to 0.56]; P = 0.002), but showed no differences in ex vivo CQ sensitivity. Parasite genotyping by microsatellites, single nucleotide polymorphism (SNP) barcoding, and whole-genome sequencing (WGS) identified a majority of homologous recurrences, with 80% (8/10) showing >98% identity by descent to paired day 0 samples. This study shows that CQ remained largely efficacious to treat P. vivax in Gia Lai; i.e., recurrences occurred late (>day 28) and in the presence of low blood CQ concentrations. However, the combination of both WGS and gene expression analysis (pvcrt) data with clinical data (PCT) allowed us to identify potential emergence of low-grade CQR, which should be closely monitored. (This study has been registered at ClinicalTrials.gov under identifier NCT02610686.).

Molecular Epidemiology of Group A Streptococcus Infections in The Gambia.

Molecular epidemiological data on Group A Streptococcus (GAS) infection in Africa is scarce. We characterized the emm-types and emm-clusters of 433 stored clinical GAS isolates from The Gambia collected between 2004 and 2018. To reduce the potential for strain mistyping, we used a newly published primer for emm-typing. There was considerable strain diversity, highlighting the need for vaccine development offering broad strain protection.

Measuring Air Quality for Advocacy in Africa (MA3): Feasibility and Practicality of Longitudinal Ambient PM2.5 Measurement Using Low-Cost Sensors.

Ambient air pollution in urban cities in sub-Saharan Africa (SSA) is an important public health problem with models and limited monitoring data indicating high concentrations of pollutants such as fine particulate matter (PM2.5). On most global air quality index maps, however, information about ambient pollution from SSA is scarce. We evaluated the feasibility and practicality of longitudinal measurements of ambient PM2.5 using low-cost air quality sensors (Purple Air-II-SD) across thirteen locations in seven countries in SSA. Devices were used to gather data over a 30-day period with the aim of assessing the efficiency of its data recovery rate and identifying challenges experienced by users in each location. The median data recovery rate was 94% (range: 72% to 100%). The mean 24 h concentration measured across all sites was 38 µg/m3 with the highest PM2.5 period average concentration of 91 µg/m3 measured in Kampala, Uganda and lowest concentrations of 15 µg/m3 measured in Faraja, The Gambia. Kampala in Uganda and Nnewi in Nigeria recorded the longest periods with concentrations >250µg/m3. Power outages, SD memory card issues, internet connectivity problems and device safety concerns were important challenges experienced when using Purple Air-II-SD sensors. Despite some operational challenges, this study demonstrated that it is reasonably practicable and feasible to establish a network of low-cost devices to provide data on local PM2.5 concentrations in SSA countries. Such data are crucially needed to raise public, societal and policymaker awareness about air pollution across SSA.

Prevalence of rheumatic heart disease in North-Central Nigeria: a school-based cross-sectional pilot study.

OBJECTIVES: To present epidemiological data on rheumatic heart disease (RHD), the most common acquired heart disease in children and young adults in low- and middle-income countries, for North-Central Nigeria. METHODS: In this pilot study, we conducted clinical and echocardiography screening on a cross section of randomly selected secondary schoolchildren in Jos, North-Central Nigeria, from March to September 2016. For outcome classification into borderline or definite RHD, we performed a confirmatory echocardiography using the World Heart Federation criteria for those suspected to have RHD from the screening. RESULTS: A total of 417 secondary schoolchildren were screened, of whom 247 (59.2%) were female. The median age was 14 years (IQR: 13-15). Clinical screening detected 8/417 children, whereas screening echocardiography detected 42/417 suspected cases of RHD. Definitive echocardiography confirmed 9/417 with RHD corresponding to a prevalence of 21.6 per 1000 (95% CI, 6.7-36.5). All but one of the confirmed RHD cases (8/9) were borderline RHD corresponding to a prevalence of 19.2 per 1000 (95% CI, 8.3-37.5) for borderline RHD and 2.4 per 1000 (95% CI, 0.1-13.3) for definite RHD. RHD was more common in boys and cardiac auscultation missed over 50% of the cases. CONCLUSIONS: This study showed a high prevalence of RHD among secondary schoolchildren in North-Central Nigeria with a vast predominance of asymptomatic borderline lesions. Larger school-based echocardiography screening using portable or handheld echocardiography aimed at early detection of subclinical RHD should be adopted.

OBJECTIFS: Présenter des données épidémiologiques sur la cardiopathie rhumatismale (CR), la maladie cardiaque acquise la plus courante chez les enfants et les jeunes adultes dans les pays à revenus faibles et intermédiaires, pour le centre-nord du Nigéria. MÉTHODES: Dans cette étude pilote, nous avons effectué un dépistage clinique et échocardiographique sur un échantillon transversal d'élèves du secondaire sélectionnés aléatoirement à Jos, dans le centre-nord du Nigéria, de mars à septembre 2016. Pour la classification des résultats en CR limite ou définitive, nous avons effectué une échocardiographie de confirmation en utilisant les critères de la Fédération Mondiale du Cœur pour les personnes suspectées d'avoir une CR lors du dépistage. RÉSULTATS: Au total, 417 élèves du secondaire ont été dépistés, dont 247 (59,2%) étaient des filles. L'âge médian était de 14 ans (IQR: 13-15). Un dépistage clinique a détecté 8/417 enfants, tandis qu'un dépistage par échocardiographie a détecté 42/417 cas suspects de CR. L'échocardiographie a confirmé une CR définitive chez 9/417, correspondant à une prévalence de 21,6 pour 1000 (IC95%: 6,7 à 36,5). Tous les cas confirmés de CR sauf un (8/9) étaient limites, correspondant à une prévalence de 19,2 pour 1000 (IC95%: 8,3 à 37,5) pour une CR limite et 2,4 pour 1000 (IC95%: 0,1 à 13,3) pour une CR définitive. La CR était plus fréquente chez les garçons et l'auscultation cardiaque a manqué plus de 50% des cas. CONCLUSIONS: Cette étude a montré une prévalence élevée de CR parmi les enfants du secondaire dans le centre-nord du Nigeria avec une forte prédominance de lésions asymptomatiques limites. Un dépistage échocardiographique à plus grande échelle en milieu scolaire utilisant une échocardiographie portable ou manuelle visant à la détection précoce de la CR subclinique devrait être adopté.

Efficacy of dihydroartemisinin/piperaquine and artesunate monotherapy for the treatment of uncomplicated Plasmodium falciparum malaria in Central Vietnam.

BACKGROUND: Artemisinin-based combination therapies (ACTs) have significantly contributed to reduce Plasmodium falciparum malaria burden in Vietnam, but their efficacy is challenged by treatment failure of dihydroartemisinin/piperaquine ACT in Southern provinces. OBJECTIVES: To assess the efficacy of dihydroartemisinin/piperaquine for uncomplicated P. falciparum malaria in Gia Lai, Central Vietnam, and determine parasite resistance to artemisinin (ClinicalTrials.gov identifier NCT02604966). METHODS: Sixty patients received either dihydroartemisinin/piperaquine (4 mg/kg/day, 3 days; n = 33) or artesunate monotherapy (4 mg/kg/day, 3 days; n = 27) followed by dihydroartemisinin/piperaquine (AS + DHA/PPQ). Clinical phenotypes were determined during a 42 day follow-up and analysed together with ex vivo susceptibility to antimalarials and molecular markers of drug resistance. RESULTS: Day 3 positivity rate was significantly higher in the AS + DHA/PPQ arm compared with dihydroartemisinin/piperaquine (70.4% versus 39.4%, P = 0.016). Parasite clearance time was 95.2 h (AS + DHA/PPQ) versus 71.9 h (dihydroartemisinin/piperaquine, P = 0.063) and parasite clearance half-life was 7.4 h (AS + DHA/PPQ) versus 7.0 h (dihydroartemisinin/piperaquine, P = 0.140). Adequate clinical and parasitological response at Day 42 was 100% in both arms. By RT-qPCR, 36% (19/53) patients remained positive until Day 7. No recurrences were detected. kelch13 artemisinin resistance mutations were found in 87% (39/45) of isolates and 50% (20/40) were KEL1/C580Y. The piperaquine resistance marker plasmepsin-2 was duplicated in 10.4% (5/48). Isolates from Day 3-positive patients (n = 18) had higher ex vivo survival rates to artemisinin compounds (P < 0.048) and prevalence of kelch13 mutations (P = 0.005) than Day 3-negative patients (n = 5). The WHO definition of artemisinin resistance was fulfilled in 60% (24/40) of cases. CONCLUSIONS: Although dihydroartemisinin/piperaquine remained effective to treat P. falciparum, the high Day 3 positivity rate and prevalence of KEL1 strains calls for continuous monitoring of dihydroartemisinin/piperaquine efficacy in Central Vietnam.

The haematological consequences of Plasmodium vivax malaria after chloroquine treatment with and without primaquine: a WorldWide Antimalarial Resistance Network systematic review and individual patient data meta-analysis.

BACKGROUND: Malaria causes a reduction in haemoglobin that is compounded by primaquine, particularly in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The aim of this study was to determine the relative contributions to red cell loss of malaria and primaquine in patients with uncomplicated Plasmodium vivax. METHODS: A systematic review identified P. vivax efficacy studies of chloroquine with or without primaquine published between January 2000 and March 2017. Individual patient data were pooled using standardised methodology, and the haematological response versus time was quantified using a multivariable linear mixed effects model with non-linear terms for time. Mean differences in haemoglobin between treatment groups at day of nadir and day 42 were estimated from this model. RESULTS: In total, 3421 patients from 29 studies were included: 1692 (49.5%) with normal G6PD status, 1701 (49.7%) with unknown status and 28 (0.8%) deficient or borderline individuals. Of 1975 patients treated with chloroquine alone, the mean haemoglobin fell from 12.22 g/dL [95% CI 11.93, 12.50] on day 0 to a nadir of 11.64 g/dL [11.36, 11.93] on day 2, before rising to 12.88 g/dL [12.60, 13.17] on day 42. In comparison to chloroquine alone, the mean haemoglobin in 1446 patients treated with chloroquine plus primaquine was - 0.13 g/dL [- 0.27, 0.01] lower at day of nadir (p = 0.072), but 0.49 g/dL [0.28, 0.69] higher by day 42 (p < 0.001). On day 42, patients with recurrent parasitaemia had a mean haemoglobin concentration - 0.72 g/dL [- 0.90, - 0.54] lower than patients without recurrence (p < 0.001). Seven days after starting primaquine, G6PD normal patients had a 0.3% (1/389) risk of clinically significant haemolysis (fall in haemoglobin > 25% to < 7 g/dL) and a 1% (4/389) risk of a fall in haemoglobin > 5 g/dL. CONCLUSIONS: Primaquine has the potential to reduce malaria-related anaemia at day 42 and beyond by preventing recurrent parasitaemia. Its widespread implementation will require accurate diagnosis of G6PD deficiency to reduce the risk of drug-induced haemolysis in vulnerable individuals. TRIAL REGISTRATION: This trial was registered with PROSPERO: CRD42016053312. The date of the first registration was 23 December 2016.

Plasmodium vivax morbidity after radical cure: A cohort study in Central Vietnam.

BACKGROUND: In Vietnam, the importance of vivax malaria relative to falciparum during the past decade has steadily increased to 50%. This, together with the spread of multidrug-resistant Plasmodium falciparum, is a major challenge for malaria elimination. A 2-year prospective cohort study to assess P. vivax morbidity after radical cure treatment and related risk factors was conducted in Central Vietnam. METHODS AND FINDINGS: The study was implemented between April 2009 and December 2011 in four neighboring villages in a remote forested area of Quang Nam province. P. vivax-infected patients were treated radically with chloroquine (CQ; 25 mg/kg over 3 days) and primaquine (PQ; 0.5 mg/kg/day for 10 days) and visited monthly (malaria symptoms and blood sampling) for up to 2 years. Time to first vivax recurrence was estimated by Kaplan-Meier survival analysis, and risk factors for first and recurrent infections were identified by Cox regression models. Among the 260 P. vivax patients (61% males [159/260]; age range 3-60) recruited, 240 completed the 10-day treatment, 223 entered the second month of follow-up, and 219 were followed for at least 12 months. Most individuals (76.78%, 171/223) had recurrent vivax infections identified by molecular methods (polymerase chain reaction [PCR]); in about half of them (55.61%, 124/223), infection was detected by microscopy, and 84 individuals (37.67%) had symptomatic recurrences. Median time to first recurrence by PCR was 118 days (IQR 59-208). The estimated probability of remaining free of recurrence by month 24 was 20.40% (95% CI [14.42; 27.13]) by PCR, 42.52% (95% CI [35.41; 49.44]) by microscopy, and 60.69% (95% CI [53.51; 67.11]) for symptomatic recurrences. The main risk factor for recurrence (first or recurrent) was prior P. falciparum infection. The main limitations of this study are the age of the results and the absence of a comparator arm, which does not allow estimating the proportion of vivax relapses among recurrent infections. CONCLUSION: A substantial number of P. vivax recurrences, mainly submicroscopic (SM) and asymptomatic, were observed after high-dose PQ treatment (5.0 mg/kg). Prior P. falciparum infection was an important risk factor for all types of vivax recurrences. Malaria elimination efforts need to address this largely undetected P. vivax transmission by simultaneously tackling the reservoir of P. falciparum and P. vivax infections.

The effect of chloroquine dose and primaquine on Plasmodium vivax recurrence: a WorldWide Antimalarial Resistance Network systematic review and individual patient pooled meta-analysis.

BACKGROUND: Chloroquine remains the mainstay of treatment for Plasmodium vivax malaria despite increasing reports of treatment failure. We did a systematic review and meta-analysis to investigate the effect of chloroquine dose and the addition of primaquine on the risk of recurrent vivax malaria across different settings. METHODS: A systematic review done in MEDLINE, Web of Science, Embase, and Cochrane Database of Systematic Reviews identified P vivax clinical trials published between Jan 1, 2000, and March 22, 2017. Principal investigators were invited to share individual patient data, which were pooled using standardised methods. Cox regression analyses with random effects for study site were used to investigate the roles of chloroquine dose and primaquine use on rate of recurrence between day 7 and day 42 (primary outcome). The review protocol is registered in PROSPERO, number CRD42016053310. FINDINGS: Of 134 identified chloroquine studies, 37 studies (from 17 countries) and 5240 patients were included. 2990 patients were treated with chloroquine alone, of whom 1041 (34·8%) received a dose below the target 25 mg/kg. The risk of recurrence was 32·4% (95% CI 29·8-35·1) by day 42. After controlling for confounders, a 5 mg/kg higher chloroquine dose reduced the rate of recurrence overall (adjusted hazard ratio [AHR] 0·82, 95% CI 0·69-0·97; p=0·021) and in children younger than 5 years (0·59, 0·41-0·86; p=0·0058). Adding primaquine reduced the risk of recurrence to 4·9% (95% CI 3·1-7·7) by day 42, which is lower than with chloroquine alone (AHR 0·10, 0·05-0·17; p<0·0001). INTERPRETATION: Chloroquine is commonly under-dosed in the treatment of vivax malaria. Increasing the recommended dose to 30 mg/kg in children younger than 5 years could reduce substantially the risk of early recurrence when primaquine is not given. Radical cure with primaquine was highly effective in preventing early recurrence and may also improve blood schizontocidal efficacy against chloroquine-resistant P vivax. FUNDING: Wellcome Trust, Australian National Health and Medical Research Council, and Bill & Melinda Gates Foundation.

Characterization of Plasmodium falciparum and Plasmodium vivax recent exposure in an area of significantly decreased transmission intensity in Central Vietnam.

BACKGROUND: In Vietnam, malaria transmission has been reduced to very low levels over the past 20 years, and as a consequence, the country aims to eliminate malaria by 2030. This study aimed to characterize the dynamics and extent of the parasite reservoir in Central Vietnam, in order to further target elimination strategies and surveillance. METHODS: A 1-year prospective cohort study (n = 429) was performed in three rural communities in Quang Nam province. Six malaria screenings were conducted between November 2014 and November 2015, including systematic clinical examination and blood sampling for malaria parasite identification, as well as molecular and serological analysis of the study population. Malaria infections were detected by light microscopy (LM) and quantitative real time PCR (qPCR), while exposure to Plasmodium falciparum and Plasmodium vivax was measured in the first and last survey by ELISA for PfAMA1, PfGLURP R2, PvAMA1, and PvMSP1-19. Classification and regression trees were used to define seropositivity and recent exposure. RESULTS: Four malaria infections (2 P. falciparum, 2 P. vivax) were detected in the same village by qPCR and/or LM. No fever cases were attributable to malaria. At the same time, the commune health centre (serving a larger area) reported few cases of confirmed malaria cases. Nevertheless, serological data proved that 13.5% of the surveyed population was exposed to P. falciparum and/or P. vivax parasites during the study period, of which 32.6% were seronegative at the start of the study, indicating ongoing transmission in the area. Risk factor analysis for seroprevalence and exposure to P. falciparum and/or P. vivax identified structural or economic risk factors and activity/behaviour-related factors, as well as spatial heterogeneity at the village level. CONCLUSIONS: Previous studies in Central Vietnam demonstrated high occurrence of asymptomatic and sub-microscopic infections. However, in this study very few asymptomatic infections were detected despite serological evidence of continued transmission. Nonetheless, the factors associated with spatial heterogeneity in transmission could be evaluated using serological classification of recent exposure, which supports the usefulness of serological methods to monitor malaria transmission.