Publications by authors named "Hannah C Slater"

Laboratory benchmarking allows objective analysis of the analytical performance of malaria rapid diagnostic tests (RDTs). We present the analytical detection limits of the Rapigen BIOCREDIT Malaria Ag Pf/Pv (pLDH/pLDH), the Rapigen BIOCREDIT Malaria Ag Pf (pLDH/HRPII), and two best-in-class WHO-prequalified comparator RDTs, generated using standardized panels containing recombinant antigen, in vitro cultured parasites, international standards, and clinical samples. Detection limit antigen concentrations of HRP2, PfLDH, and PvLDH were determined for the Rapigen and comparator RDTs.

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Article Synopsis
  • Progress in malaria control has stagnated, requiring national malaria control programs (NMCPs) to make data-driven decisions for effective vector control amid rising insecticide resistance.
  • There's a growing need for country-specific frameworks to integrate various data sources—like health systems data and vector control program data—to evaluate both existing and new interventions.
  • Key recommendations for improving evaluations include ensuring quality data collection, selecting key indicators for impact assessment, and considering multiple contextual factors to enhance decision-making processes in vector control strategies.
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Background: The gains made against malaria have stagnated since 2015, threatened further by increasing resistance to insecticides and antimalarials. Improvement in malaria control necessitates a multipronged strategy, which includes the development of novel tools. One such tool is mass drug administration (MDA) with endectocides, primarily ivermectin, which has shown promise in reducing malaria transmission through lethal and sublethal impacts on the mosquito vector.

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Article Synopsis
  • Rapid diagnostic tests (RDTs) are crucial for detecting malaria, especially in pregnancy, and a new highly sensitive rapid diagnostic test (HS-RDT) shows promise for improving diagnosis and outcomes in malaria-endemic regions.
  • A review of thirteen studies comparing HS-RDT with conventional RDT (co-RDT) and molecular methods found varying sensitivity rates for both tests, with HS-RDT generally performing better in detecting low parasite densities.
  • Despite its higher analytical sensitivity, the clinical advantages of HS-RDT over co-RDT were marginal and not statistically significant, indicating a need for further research to fully assess the benefits of RDT improvements.
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Background: A new more highly sensitive rapid diagnostic test (HS-RDT) for Plasmodium falciparum malaria (Alere™/Abbott Malaria Ag P.f RDT [05FK140], now called NxTek™ Eliminate Malaria Ag Pf) was launched in 2017. The test has already been used in many research studies in a wide range of geographies and use cases.

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Article Synopsis
  • Cluster-randomized trials are useful for evaluating community-level interventions, particularly for controlling vector-borne diseases, but studying multiple clusters can be challenging due to the complexity of monitoring.
  • A study explored three analysis frameworks (mixed-effects models, generalized estimating equations, and cluster-level analyses) across different cluster-randomized trial designs, specifically for repeated ivermectin drug administrations to control malaria.
  • The findings indicated that mixed-effects models with small sample corrections provided high statistical power and proper control of errors, while crossover designs generally performed better than parallel designs in terms of power, especially as the number of clusters increased.
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Background: Reactive malaria strategies are predicated on the assumption that individuals infected with malaria are clustered within households or neighbourhoods. Despite the widespread programmatic implementation of reactive strategies, little empirical evidence exists as to whether such strategies are appropriate and, if so, how they should be most effectively implemented.

Methods And Findings: We collated 2 different datasets to assess clustering of malaria infections within households: (i) demographic health survey (DHS) data, integrating household information and patent malaria infection, recent fever, and recent treatment status in children; and (ii) data from cross-sectional and reactive detection studies containing information on the household and malaria infection status (patent and subpatent) of all-aged individuals.

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Substantial progress has been made globally to control malaria, however there is a growing need for innovative new tools to ensure continued progress. One approach is to harness genetic sequencing and accompanying methodological approaches as have been used in the control of other infectious diseases. However, to utilize these methodologies for malaria, we first need to extend the methods to capture the complex interactions between parasites, human and vector hosts, and environment, which all impact the level of genetic diversity and relatedness of malaria parasites.

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Background: The recent expansion of tools designed to accurately quantify malaria parasite-produced antigens has enabled us to evaluate the performance of rapid diagnostic tests (RDTs) as a function of the antigens they detect-typically histidine rich protein 2 (HRP2) or lactate dehydrogenase (LDH).

Methods: For this analysis, whole blood specimens from a longitudinal study in Bancoumana, Mali were used to evaluate the performance of the ultra-sensitive HRP2-based Alere™ Malaria Ag P.f RDT (uRDT).

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The burden of malaria is heavily concentrated in sub-Saharan Africa (SSA) where cases and deaths associated with COVID-19 are rising. In response, countries are implementing societal measures aimed at curtailing transmission of SARS-CoV-2. Despite these measures, the COVID-19 epidemic could still result in millions of deaths as local health facilities become overwhelmed.

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Background: In 2016, the Zambian National Malaria Elimination Centre started programmatic mass drug administration (pMDA) campaigns with dihydroartemisinin-piperaquine as a malaria elimination tool in Southern Province. Two rounds were administered, 2 months apart (coverage 70% and 57%, respectively). We evaluated the impact of 1 year of pMDA on malaria incidence using routine data.

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Background: Ivermectin is a potential new vector control tool to reduce malaria transmission. Mosquitoes feeding on a bloodmeal containing ivermectin have a reduced lifespan, meaning they are less likely to live long enough to complete sporogony and become infectious. We aimed to estimate the effect of ivermectin on malaria transmission in various scenarios of use.

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Surveillance and diagnosis of malaria relies predominantly on rapid diagnostic tests (RDT). However, false-negative (FN) RDT results are known to occur for a variety of reasons, including operator error, poor storage conditions, gene deletions, poor performance of specific RDT brands and lots, and low-parasite density infections. We used RDT and microscopy results from 85 000 children enrolled in Demographic Health Surveys and Malaria Indicator Surveys from 2009 to 2015 across 19 countries to explore the distribution of and risk factors for FN-RDTs in sub-Saharan Africa, where malaria's impact is greatest.

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Ten countries have reported gene deletions since the first observation of -deleted parasites in 2012. In a previous study (Watson et al., 2017), we characterised the drivers selecting for deletions and mapped the regions in Africa with the greatest selection pressure.

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Malaria infections occurring below the limit of detection of standard diagnostics are common in all endemic settings. However, key questions remain surrounding their contribution to sustaining transmission and whether they need to be detected and targeted to achieve malaria elimination. In this study we analyse a range of malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections.

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Background: Ivermectin is widely used in mass drug administrations for controlling neglected parasitic diseases, and can be lethal to malaria vectors that bite treated humans. Therefore, it could be a new tool to reduce plasmodium transmission. We tested the hypothesis that frequently repeated mass administrations of ivermectin to village residents would reduce clinical malaria episodes in children and would be well tolerated with minimal harms.

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Background: Ivermectin is being considered for mass drug administration for malaria due to its ability to kill mosquitoes feeding on recently treated individuals. However, standard, single doses of 150-200 μg/kg used for onchocerciasis and lymphatic filariasis have a short-lived mosquitocidal effect (<7 days). Because ivermectin is well tolerated up to 2000 μg/kg, we aimed to establish the safety, tolerability, and mosquitocidal efficacy of 3 day courses of high-dose ivermectin, co-administered with a standard malaria treatment.

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Background: The majority of Plasmodium vivax and Plasmodium falciparum infections in low-endemic settings are asymptomatic. The relative contribution to the infectious reservoir of these infections compared to clinical malaria cases is currently unknown.

Methods: We assessed infectivity of passively recruited symptomatic malaria patients (n = 41) and community-recruited asymptomatic individuals with microscopy-detected (n = 41) and polymerase chain reaction (PCR)-detected infections (n = 82) using membrane feeding assays with Anopheles arabiensis mosquitoes in Adama, Ethiopia.

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Article Synopsis
  • Despite progress in reducing malaria, many people remain at risk, and continued funding from the President's Malaria Initiative (PMI) is crucial to sustain and advance these gains.
  • The study utilized a mathematical model to assess PMI's contributions, estimating they have prevented approximately 185 million malaria cases and saved nearly 940,000 lives since 2005, with ongoing interventions set to avert even more cases and deaths.
  • A potential 44% cut in PMI funding could lead to an increase of around 67 million malaria cases and nearly 291,000 deaths from 2017 to 2020, demonstrating the significant impact of financial support on malaria control.
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Rapid diagnostic tests (RDTs) have transformed malaria diagnosis. The most prevalent RDTs detect histidine-rich protein 2 (PfHRP2). However, gene deletions yielding false-negative RDTs, first reported in South America in 2010, have been confirmed in Africa and Asia.

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Background: Mass drug administration for elimination of Plasmodium falciparum malaria is recommended by WHO in some settings. We used consensus modelling to understand how to optimise the effects of mass drug administration in areas with low malaria transmission.

Methods: We collaborated with researchers doing field trials to establish a standard intervention scenario and standard transmission setting, and we input these parameters into four previously published models.

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Background: Transmission-blocking interventions (TBIs) aim to eliminate malaria by reducing transmission of the parasite between the host and the invertebrate vector. TBIs include transmission-blocking drugs and vaccines that, when given to humans, are taken up by mosquitoes and inhibit parasitic development within the vector. Accurate methodologies are key to assess TBI efficacy to ensure that only the most potent candidates progress to expensive and time-consuming clinical trials.

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