Publications

Journal article

Hellewell J, Sherrard-Smith E, Ogoma S, Churcher TSet al., 2021,

Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria

, Philosophical Transactions of the Royal Society B: Biological Sciences, Vol: 376, Pages: 1-9, ISSN: 0962-8436

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality.

Journal article

Guglielmo F, Sanou A, Churcher TS, Ferguson HM, Ranson H, Sherrard-Smith Eet al., 2021,

Quantifying individual variability in exposure risk to mosquito bites in the Cascades region, Burkina Faso

, Malaria Journal, Vol: 20, Pages: 1-14, ISSN: 1475-2875

BackgroundThe Cascades region, Burkina Faso, has a high malaria burden despite reported high insecticide-treated mosquito net (ITN) use. Human and vector activities outside the hours when indoor interventions offer direct protection from infectious bites potentially increase exposure risk to bites from malaria-transmitting Anopheles mosquitoes. This work investigated the degree of variation in human behaviour both between individuals and through time (season) to quantify how it impacts exposure to malaria vectors.MethodsPatterns in human overnight activity (18:00–06:00) to quantify time spent using an ITN across 7 successive nights in two rural communities, Niakore (N = 24 participants) and Toma (71 participants), were observed in the dry and rainy seasons, between 2017 and 2018. Hourly human landing Anopheles mosquito catches were conducted in Niakore specifically, and Cascades region generally, between 2016 and 2017. Data were statistically combined to estimate seasonal variation in time spent outdoors and Anopheles bites received per person per night (bpppn).ResultsSubstantial variability in exposure to outdoor Anopheles bites was detected within and between communities across seasons. In October, when Anopheles densities are highest, an individual’s risk of Anopheles bites ranged from 2.2 to 52.2 bites per person per night (bpppn) within the same week with variable risk dependent on hours spent indoors. Comparably higher outdoor human activity was observed in April and July but, due to lower Anopheles densities estimated, bpppn were 0.2–4.7 and 0.5–32.0, respectively. Males and people aged over 21 years were predicted to receive more bites in both sentinel villages.ConclusionThis work presents one of the first clear descriptions of the degree of heterogeneity in time spent outdoors between people and across the year. Appreciation of sociodemographic, cultural and entomological activities will help refine approaches to vector

Journal article

Guglielmo F, Sanou A, Churcher TS, Ferguson HM, Ranson H, Sherrard-Smith Eet al., 2020,

Quantifying the individual variability in people’s exposure to mosquito bites in Burkina Faso

, Malaria Journal

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background</jats:bold>The Cascades Region, Burkina Faso, has high malaria burden despite reported high insecticide treated bed net (ITN) use. Human and vector activities outside the hours when indoor interventions offer direct protection from infectious bites potentially increase exposure risk to bites from malaria-transmitting <jats:italic>Anopheles </jats:italic>mosquitoes. We investigate the degree of variation in human behaviour both between individuals and through time (season) to quantify how it impacts exposure to malaria vectors.<jats:bold>Methods</jats:bold>Patterns in human overnight activity (18:00-06:00) to quantify time spent using an ITN across 7 successive nights in two rural communities, Niakore (N = 24 participants) and Toma (71 participants), were observed in the dry and rainy seasons, between 2017-2018. Hourly human landing <jats:italic>Anopheles </jats:italic>mosquito catches were conducted in Niakore specifically, and Cascades Region generally, between 2016-2017. Data were statistically combined to estimate seasonal variation in time spent outdoors and <jats:italic>Anopheles </jats:italic>bites received per person per night (bpppn).<jats:bold>Results</jats:bold>Substantial variability in exposure to outdoor <jats:italic>Anopheles</jats:italic> bites was detected within and between communities and across seasons. In October, when <jats:italic>Anopheles </jats:italic>densities are highest, an individual’s risk of <jats:italic>Anopheles</jats:italic> bites ranged from 2.2 to 52.2 bpppn within the same week with variable risk dependent on hours spent indoors. Comparably higher outdoor human activity was observed in April and July but, due to lower <jats:italic>Anopheles </jats:italic>densities estimated bpppn were 0.2 – 4.7 bpppn, and 0.5 &nda

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Journal article

Witmer K, Dahalan F, Delves M, Yahiya S, Watson O, Straschil U, Chiwcharoen D, Sorboon B, Pukrittayakamee S, Pearson R, Howick V, Lawniczak M, White N, Dondorp A, Okell L, Chotivanich K, Ruecker A, Baum Jet al., 2021,

Transmission of artemisinin-resistant malaria parasites to mosquitoes under antimalarial drug pressure

, Antimicrobial Agents and Chemotherapy, Vol: 65, Pages: 1-17, ISSN: 0066-4804

Resistance to artemisinin-based combination therapy (ACT) in the Plasmodium falciparum parasite is threatening to reverse recent gains in reducing global deaths from malaria. Whilst resistance manifests as delayed parasite clearance in patients the phenotype can only spread geographically via the sexual stages and mosquito transmission. In addition to their asexual killing properties, artemisinin and its derivatives sterilise sexual male gametocytes. Whether resistant parasites overcome this sterilising effect has not, however, been fully tested. Here, we analysed P. falciparum clinical isolates from the Greater Mekong Subregion, each demonstrating delayed clinical clearance and known resistance-associated polymorphisms in Kelch13 (PfK13var). As well as demonstrating reduced asexual sensitivity to drug, certain PfK13var isolates demonstrated a marked reduction in sensitivity to artemisinin in an in vitro male gamete formation assay. Importantly, this same reduction in sensitivity was observed when the most resistant isolate was tested directly in mosquito feeds. These results indicate that, under artemisinin drug pressure, whilst sensitive parasites are blocked, resistant parasites continue transmission. This selective advantage for resistance transmission could favour acquisition of additional host-specificity or polymorphisms affecting partner drug sensitivity in mixed infections. Favoured resistance transmission under ACT coverage could have profound implications for the spread of multidrug resistant malaria beyond Southeast Asia.

Journal article

Mumtaz R, Okell LC, Challenger J, 2020,

Asymptomatic recrudescence after artemether-lumefantrine treatment for uncomplicated falciparum malaria: a systematic review and meta-analysis

, Malaria Journal, Vol: 19, ISSN: 1475-2875

BackgroundIn clinical trials of therapy for uncomplicated Plasmodium falciparum, there are usually some patients who fail treatment even in the absence of drug resistance. Treatment failures, which can be due to recrudescence or re-infection, are categorized as ‘clinical’ or ‘parasitological’ failures, the former indicating that symptoms have returned. Asymptomatic recrudescence has public health implications for continued malaria transmission and may be important for the spread of drug-resistant malaria. As the number of recrudescences in an individual trial is often low, it is difficult to assess how commonplace asymptomatic recrudescence is, and with what factors it is associated.MethodsA systematic literature review was carried out on clinical trials of artemether-lumefantrine (AL) in patients seeking treatment for symptomatic uncomplicated falciparum malaria, and information on symptoms during treatment failure was recorded. Only treatment failures examined by polymerase chain reaction (PCR) were included, so as to exclude re-infections. A multivariable Bayesian regression model was used to explore factors potentially explaining the proportion of recrudescent infections which are symptomatic across the trials included in the study.ResultsAcross 60 published trials, including 9137 malaria patients, 37.8% [95% CIs (26.6–49.4%)] of recrudescences were symptomatic. A positive association was found between transmission intensity and the observed proportion of recrudescences that were asymptomatic. Symptoms were more likely to return in trials that only enrolled children aged < 72 months [odds ratio = 1.62, 95% CIs (1.01, 2.59)]. However, 84 studies had to be excluded from this analysis, as recrudescences were not specified as symptomatic or asymptomatic.ConclusionsAL, the most widely used treatment for uncomplicated P. falciparum in Africa, remains a highly efficacious drug in most endemic countries. Howev

Journal article

Hogan A, Winskill P, Ghani A, 2020,

Estimated impact of RTS,S/AS01 malaria vaccine allocation strategies in sub-Saharan Africa: a modelling study

, PLoS Medicine, Vol: 17, Pages: 1-19, ISSN: 1549-1277

Background: The RTS,S/AS01 vaccine against P. falciparum malaria infection completed phase 3 trials in 2014, and demonstrated efficacy against clinical malaria of approximately 36% over 4 years for a 4-dose schedule in children aged 5–17 months. Pilot vaccine implementation has recently begun in three African countries. If the pilots demonstrate both a positive health impact and resolve remaining safety concerns, wider roll-out could be recommended from 2021 onwards. Vaccine demand may however outstrip initial supply. We sought to identify where vaccine introduction should be prioritised to maximise public health impact under a range of supply constraints using mathematical modelling. Methods and Findings: Using a mathematical model of P. falciparum malaria transmission and RTS,S vaccine impact, we estimated the clinical cases and deaths averted in children aged 0–5 years in sub-Saharan Africa under two scenarios for vaccine coverage (100% and realistic) and two scenarios for other interventions (current coverage and WHO Global Technical Strategy targets). We used a prioritisation algorithm to identify potential allocative efficiency gains fromprioritising vaccine allocation among countries or administrative units to maximise cases or deaths averted. If malaria burden at introduction is similar to current levels, assuming realistic vaccine coverage and country-level prioritisation in areas with parasite prevalence >10%, we estimate 4.3 million (95% credible interval, CrI 2.8–6.8 million) malaria cases and 22,000 (95% CrI 11,000–35,000) deaths in children younger than 5 years could be averted annually at a dose constraint of 30 million. This decreases to 3.0 million (95% CrI 2.0–4.7 million) cases and14,000 (95% CrI 7,000–23,000) deaths at a dose constraint of 20 million,and increases to 6.6 million (95% CrI 4.2–10.8 million) cases and38,000 (95% CrI 18

Journal article

Morang'a CM, Amenga-Etego L, Bah SY, Appiah V, Amuzu DSY, Amoako N, Abugri J, Oduro AR, Cunnington AJ, Awandare GA, Otto TDet al., 2020,

Machine learning approaches classify clinical malaria outcomes based on haematological parameters

, BMC Medicine, Vol: 18, ISSN: 1741-7015

BACKGROUND: Malaria is still a major global health burden, with more than 3.2 billion people in 91 countries remaining at risk of the disease. Accurately distinguishing malaria from other diseases, especially uncomplicated malaria (UM) from non-malarial infections (nMI), remains a challenge. Furthermore, the success of rapid diagnostic tests (RDTs) is threatened by Pfhrp2/3 deletions and decreased sensitivity at low parasitaemia. Analysis of haematological indices can be used to support the identification of possible malaria cases for further diagnosis, especially in travellers returning from endemic areas. As a new application for precision medicine, we aimed to evaluate machine learning (ML) approaches that can accurately classify nMI, UM, and severe malaria (SM) using haematological parameters. METHODS: We obtained haematological data from 2,207 participants collected in Ghana: nMI (n = 978), SM (n = 526), and UM (n = 703). Six different ML approaches were tested, to select the best approach. An artificial neural network (ANN) with three hidden layers was used for multi-classification of UM, SM, and uMI. Binary classifiers were developed to further identify the parameters that can distinguish UM or SM from nMI. Local interpretable model-agnostic explanations (LIME) were used to explain the binary classifiers. RESULTS: The multi-classification model had greater than 85% training and testing accuracy to distinguish clinical malaria from nMI. To distinguish UM from nMI, our approach identified platelet counts, red blood cell (RBC) counts, lymphocyte counts, and percentages as the top classifiers of UM with 0.801 test accuracy (AUC = 0.866 and F1 score = 0.747). To distinguish SM from nMI, the classifier had a test accuracy of 0.96 (AUC = 0.983 and F1 score = 0.944) with mean platelet volume and mean cell volume being the unique classifiers of SM. Random forest was used

Journal article

Thompson H, Hogan A, Walker P, White M, Cunnington A, Ockenhouse C, Ghani Aet al., 2020,

Modelling the roles of antibody titre and avidity in protection from Plasmodium falciparum malaria infection following RTS,S/AS01 vaccination

, Vaccine, Vol: 38, Pages: 7498-7507, ISSN: 0264-410X

Anti-circumsporozoite antibody titres have been established as an essential indicator for evaluating the immunogenicity and protective capacity of the RTS,S/AS01 malaria vaccine. However, a new delayed-fractional dose regime of the vaccine was recently shown to increase vaccine efficacy, from 62.5% (95% CI 29.4–80.1%) under the original dosing schedule to 86.7% (95% CI, 66.8–94.6%) without a corresponding increase in antibody titres. Here we reanalyse the antibody data from this challenge trial to determine whether IgG avidity may help to explain efficacy better than IgG titre alone by adapting a within-host mathematical model of sporozoite inoculation. We demonstrate that a model incorporating titre and avidity provides a substantially better fit to the data than titre alone. These results also suggest that in individuals with a high antibody titre response that also show high avidity (both metrics in the top tercile of observed values) delayed-fractional vaccination provided near perfect protection upon first challenge (98.2% [95% Credible Interval 91.6–99.7%]). This finding suggests that the quality of the vaccine induced antibody response is likely to be an important determinant in the development of highly efficacious pre-erythrocytic vaccines against malaria.

Journal article

Eagon S, Hammill JT, Sigal M, Ahn KJ, Tryhorn JE, Koch G, Belanger B, Chaplan CA, Loop L, Kashtanova AS, Yniguez K, Lazaro H, Wilkinson SP, Rice AL, Falade MO, Takahashi R, Kim K, Cheung A, DiBernardo C, Kimball JJ, Winzeler EA, Eribez K, Mittal N, Gamo F-J, Crespo B, Churchyard A, Garcia-Barbazan I, Baum J, Anderson MO, Laleu B, Guy RKet al., 2020,

Synthesis and Structure-Activity Relationship of Dual-Stage Antimalarial Pyrazolo[3,4-<i>b</i>]pyridines

, JOURNAL OF MEDICINAL CHEMISTRY, Vol: 63, Pages: 11902-11919, ISSN: 0022-2623

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Citations: 13

Journal article

Mousa A, Al-Taiar A, Anstey NM, Badaut C, Barber BE, Bassat Q, Challenger J, Cunnington AJ, Datta D, Drakeley C, Ghani AC, Gordeuk VR, Grigg MJ, Hugo P, John CC, Mayor A, Migot-Nabias F, Opoka RO, Pasvol G, Rees C, Reyburn H, Riley EM, Shah BN, Sitoe A, Sutherland CJ, Thuma PE, Unger SA, Viwami F, Walther M, Whitty CJM, William T, Okell LCet al., 2020,

The impact of delayed treatment of uncomplicated P. falciparum malaria on progression to severe malaria: a systematic review and a pooled multicentre individual-patient meta-analysis

, PLoS Medicine, Vol: 17, Pages: 1-28, ISSN: 1549-1277

Background: Delay in receiving treatment for uncomplicated malaria is often reported to increase the risk of developing severe malaria, but access to treatment remains low in most high-burden areas. Understanding the contribution of treatment delay on progression to severe disease is critical to determine how quickly patients need to receive treatment and to quantify the impact of widely implemented treatment interventions, such as “test-and-treat” policies administered by community health workers. We conducted a pooled individual-participant meta-analysis to estimate the association between treatment delay and presenting with severe malaria.Methods and Findings: A search using Ovid MEDLINE and Embase was initially conducted to identify studies on severe P. falciparum malaria which included information on treatment delay, such as fever duration 12(inceptions to 22nd September 2017). Studies identified included five case-control and eight other observational clinical studies of severe and uncomplicated malaria cases. Risk of bias was assessed using the Newcastle–Ottawa scale and all studies were ranked as “Good”, scoring ≥7/10. Individual-patient data were pooled from thirteen studies of 3,989(94.1% aged <15 years)severe malaria patients and 5,780(79.6% aged <15 years)uncomplicated malaria cases in Benin, Malaysia, Mozambique, Tanzania, The Gambia, Uganda, Yemen and Zambia. Definitions of severe malaria were standardised across studies to compare treatment delay in patients with uncomplicated malaria and different severe malaria phenotypes using age-adjusted mixed-effects regression. The odds of any severe malaria phenotype were significantly higher in children with longer delays between initial symptoms and arrival at the health facility (OR=1.33, 95%CI:1.07-1.64 for a delay of >24 hours vs. ≤24 hours;p=0.009). Reported illness duration was a strong predictor of presenting with severe malarial anaemia (SMA) in children

Journal article

Prah DA, Amoah LE, Gibbins MP, Bediako Y, Cunnington AJ, Awandare GA, Hafalla JCRet al., 2020,

Comparison of leucocyte profiles between healthy children and those with asymptomatic and symptomatic Plasmodium falciparum infections.

, Malaria Journal, Vol: 19, Pages: 364-364, ISSN: 1475-2875

BACKGROUND: The immune mechanisms that determine whether a Plasmodium falciparum infection would be symptomatic or asymptomatic are not fully understood. Several studies have been carried out to characterize the associations between disease outcomes and leucocyte numbers. However, the majority of these studies have been conducted in adults with acute uncomplicated malaria, despite children being the most vulnerable group. METHODS: Peripheral blood leucocyte subpopulations were characterized in children with acute uncomplicated (symptomatic; n = 25) or asymptomatic (n = 67) P. falciparum malaria, as well as malaria-free (uninfected) children (n = 16) from Obom, a sub-district of Accra, Ghana. Leucocyte subpopulations were enumerated by flow cytometry and correlated with two measures of parasite load: (a) plasma levels of P. falciparum histidine-rich protein 2 (PfHRP2) as a proxy for parasite biomass and (b) peripheral blood parasite densities determined by microscopy. RESULTS: In children with symptomatic P. falciparum infections, the proportions and absolute cell counts of total (CD3 +) T cells, CD4 + T cells, CD8 + T cells, CD19 + B cells and CD11c + dendritic cells (DCs) were significantly lower as compared to asymptomatic P. falciparum-infected and uninfected children. Notably, CD15 + neutrophil proportions and cell counts were significantly increased in symptomatic children. There was no significant difference in the proportions and absolute counts of CD14 + monocytes amongst the three study groups. As expected, measures of parasite load were significantly higher in symptomatic cases. Remarkably, PfHRP2 levels and parasite densities negatively correlated with both the proportions and absolute numbers of peripheral leucocyte subsets: CD3 + T, CD4 + T, CD8 + T, CD19 + B, CD56&th

Journal article

Djaafara BA, Whittaker C, Watson OJ, Verity R, Brazeau NF, Widyastuti W, Oktavia D, Adrian V, Salama N, Bhatia S, Nouvellet P, Sherrard-Smith E, Churcher TS, Surendra H, Lina RN, Ekawati LL, Lestari KD, Andrianto A, Thwaites G, Baird JK, Ghani AC, Elyazar IRF, Walker PGTet al., 2020,

Quantifying the dynamics of COVID-19 burden and impact of interventions in Java, Indonesia

<jats:title>ABSTRACT</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>As in many countries, quantifying COVID-19 spread in Indonesia remains challenging due to testing limitations. In Java, non-pharmaceutical interventions (NPIs) were implemented throughout 2020. However, as a vaccination campaign launches, cases and deaths are rising across the island.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We used modelling to explore the extent to which data on burials in Jakarta using strict COVID-19 protocols (C19P) provide additional insight into the transmissibility of the disease, epidemic trajectory, and the impact of NPIs. We assess how implementation of NPIs in early 2021 will shape the epidemic during the period of likely vaccine roll-out.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>C19P burial data in Jakarta suggest a death toll approximately 3.3 times higher than reported. Transmission estimates using these data suggest earlier, larger, and more sustained impact of NPIs. Measures to reduce sub-national spread, particularly during Ramadan, substantially mitigated spread to more vulnerable rural areas. Given current trajectory, daily cases and deaths are likely to increase in most regions as the vaccine is rolled-out. Transmission may peak in early 2021 in Jakarta if current levels of control are maintained. However, relaxation of control measures is likely to lead to a subsequent resurgence in the absence of an effective vaccination campaign.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>Syndromic measures of mortality provide a more complete picture of COVID-19 severity upon which to base decision-making. The high potential impact of the vaccine in Java is attributable to reductions in transmission to date and dependent on these be

Journal article

Ashdown G, Gaboriau D, Baum J, 2020,

A machine learning approach to define antimalarial drug action from heterogeneous cell-based screens

, Science Advances, Vol: 6, ISSN: 2375-2548

Drug resistance threatens the effective prevention and treatment of an ever-increasing range ofhuman infections. This highlights an urgent need for new and improved drugs with novelmechanisms of action to avoid cross-resistance. Current cell-based drug screens are,however, restricted to binary live/dead readouts with no provision for mechanism of actionprediction. Machine learning methods are increasingly being used to improve informationextraction from imaging data. Such methods, however, work poorly with heterogeneouscellular phenotypes and generally require time-consuming human-led training. We havedeveloped a semi-supervised machine learning approach, combining human- and machinelabelled training data from mixed human malaria parasite cultures. Designed for highthroughput and high-resolution screening, our semi-supervised approach is robust to naturalparasite morphological heterogeneity and correctly orders parasite developmental stages. Ourapproach also reproducibly detects and clusters drug-induced morphological outliers bymechanism of action, demonstrating the potential power of machine learning for acceleratingcell-based drug discovery.

Journal article

Watson O, Okell L, Hellewell J, Slater H, Unwin H, Omedo I, Bejon P, Snow R, Noor A, Rockett K, Hubbart C, Joaniter N, Greenhouse B, Chang H-H, Ghani A, Verity Aet al., 2020,

Evaluating the performance of malaria genetics for inferring changes in transmission intensity using transmission modelling

, Molecular Biology and Evolution, Vol: 38, Pages: 274-289, ISSN: 0737-4038

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 utilise 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. We develop an individual-based transmission model to simulate malaria parasite genetics parameterised using estimated relationships between complexity of infection and age from 5 regions in Uganda and Kenya. We predict that cotransmission and superinfection contribute equally to within-host parasite genetic diversity at 11.5% PCR prevalence, above which superinfections dominate. Finally, we characterise the predictive power of six metrics of parasite genetics for detecting changes in transmission intensity, before grouping them in an ensemble statistical model. The model predicted malaria prevalence with a mean absolute error of 0.055. Different assumptions about the availability of sample metadata were considered, with the most accurate predictions of malaria prevalence made when the clinical status and age of sampled individuals is known. Parasite genetics may provide a novel surveillance tool for estimating the prevalence of malaria in areas in which prevalence surveys are not feasible. However, the findings presented here reinforce the need for patient metadata to be recorded and made available within all future attempts to use parasite genetics for surveillance.

Journal article

Hogan A, Jewell B, Sherrard-Smith E, Watson O, Whittaker C, Hamlet A, Smith J, Winskill P, Verity R, Baguelin M, Lees J, Whittles L, Ainslie K, Bhatt S, Boonyasiri A, Brazeau N, Cattarino L, Cooper L, Coupland H, Cuomo-Dannenburg G, Dighe A, Djaafara A, Donnelly C, Eaton J, van Elsland S, Fitzjohn R, Fu H, Gaythorpe K, Green W, Haw D, Hayes S, Hinsley W, Imai N, Laydon D, Mangal T, Mellan T, Mishra S, Parag K, Thompson H, Unwin H, Vollmer M, Walters C, Wang H, Ferguson N, Okell L, Churcher T, Arinaminpathy N, Ghani A, Walker P, Hallett Tet al., 2020,

Potential impact of the COVID-19 pandemic on HIV, TB and malaria in low- and middle-income countries: a modelling study

, The Lancet Global Health, Vol: 8, Pages: e1132-e1141, ISSN: 2214-109X

Background: COVID-19 has the potential to cause substantial disruptions to health services, including by cases overburdening the health system or response measures limiting usual programmatic activities. We aimed to quantify the extent to which disruptions in services for human immunodeficiency virus (HIV), tuberculosis (TB) and malaria in low- and middle-income countries with high burdens of those disease could lead to additional loss of life. Methods: We constructed plausible scenarios for the disruptions that could be incurred during the COVID-19 pandemic and used established transmission models for each disease to estimate the additional impact on health that could be caused in selected settings.Findings: In high burden settings, HIV-, TB- and malaria-related deaths over five years may increase by up to 10%, 20% and 36%, respectively, compared to if there were no COVID-19 pandemic. We estimate the greatest impact on HIV to be from interruption to antiretroviral therapy, which may occur during a period of high health system demand. For TB, we estimate the greatest impact is from reductions in timely diagnosis and treatment of new cases, which may result from any prolonged period of COVID-19 suppression interventions. We estimate that the greatest impact on malaria burden could come from interruption of planned net campaigns. These disruptions could lead to loss of life-years over five years that is of the same order of magnitude as the direct impact from COVID-19 in places with a high burden of malaria and large HIV/TB epidemics.Interpretation: Maintaining the most critical prevention activities and healthcare services for HIV, TB and malaria could significantly reduce the overall impact of the COVID-19 pandemic.Funding: Bill & Melinda Gates Foundation, The Wellcome Trust, DFID, MRC

Journal article

Mumtaz R, Okell LC, Challenger JD, 2020,

How often do symptoms return after unsuccessful drug treatment for malaria? A systematic review and meta-analysis

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>In clinical trials of therapies for uncomplicated <jats:italic>Plasmodium falciparum</jats:italic>, there are usually some patients who fail treatment even in the absence of drug resistance. Treatment failures are categorised as ‘clinical’ or ‘parasitological’ failures, the latter indicating that recrudescence of the infection has occurred without inducing the return of symptoms. Asymptomatic treatment failure has public health implications for continued malaria transmission and may be important for the spread of drug-resistant malaria. As the number of treatment failures in an individual trial is often low, it is difficult to assess how commonplace asymptomatic treatment failure is, and with what factors it is associated.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>A systematic literature review was carried out on clinical trials of artemether-lumefantrine (AL) in patients seeking treatment for symptomatic uncomplicated falciparum malaria, and information on symptoms during treatment failure was recorded. Only treatment failures examined by polymerase chain reaction (PCR) were included, so as to exclude reinfections. Using a multivariable Bayesian regression model, we explored factors potentially explaining the proportion of recrudescent infections which are symptomatic across the trials included in our study.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Across 60 published trials including 9137 malaria patients we found that 40.8% (95% CIs [35.9-45.8%]) of late treatment failures were symptomatic. We found a positive association between transmission intensity and the observed proportion of treatment failures that were asymptomatic. We also found that symptoms were more likely to return in t

Journal article

Wang X, Wilkinson MD, Lin X, Ren R, Willison KR, Ivanov AP, Baum J, Edel JBet al., 2020,

Correction: Single-molecule nanopore sensing of actin dynamics and drug binding

, Chemical Science, Vol: 11, Pages: 8036-8038, ISSN: 2041-6520

Correction for ‘Single-molecule nanopore sensing of actin dynamics and drug binding’ by Xiaoyi Wang et al., Chem. Sci., 2020, 11, 970–979, DOI: 10.1039/C9SC05710B.

Journal article

Sherrard-Smith E, Hogan AB, Hamlet A, Watson OJ, Whittaker C, Winskill P, Ali F, Mohammad AB, Uhomoibhi P, Maikore I, Ogbulafor N, Nikau J, Kont MD, Challenger JD, Verity R, Lambert B, Cairns M, Rao B, Baguelin M, Whittles LK, Lees JA, Bhatia S, Knock ES, Okell L, Slater HC, Ghani AC, Walker PGT, Okoko OO, Churcher TSet al., 2020,

The potential public health consequences of COVID-19 on malaria in Africa.

, Nature Medicine, Vol: 26, Pages: 1411-1416, ISSN: 1078-8956

The burden of malaria is heavily concentrated in sub-Saharan Africa (SSA) where cases and deaths associated with COVID-19 are rising1. In response, countries are implementing societal measures aimed at curtailing transmission of SARS-CoV-22,3. Despite these measures, the COVID-19 epidemic could still result in millions of deaths as local health facilities become overwhelmed4. Advances in malaria control this century have been largely due to distribution of long-lasting insecticidal nets (LLINs)5, with many SSA countries having planned campaigns for 2020. In the present study, we use COVID-19 and malaria transmission models to estimate the impact of disruption of malaria prevention activities and other core health services under four different COVID-19 epidemic scenarios. If activities are halted, the malaria burden in 2020 could be more than double that of 2019. In Nigeria alone, reducing case management for 6 months and delaying LLIN campaigns could result in 81,000 (44,000-119,000) additional deaths. Mitigating these negative impacts is achievable, and LLIN distributions in particular should be prioritized alongside access to antimalarial treatments to prevent substantial malaria epidemics.

Journal article

Suh E, Grossman MK, Waite JL, Dennington NL, Sherrard-Smith E, Churcher TS, Thomas MBet al., 2020,

The influence of feeding behaviour and temperature on the capacity of mosquitoes to transmit malaria

, Nature Ecology and Evolution, Vol: 4, Pages: 940-951, ISSN: 2397-334X

Insecticide-treated bed nets reduce malaria transmission by limiting contact between mosquito vectors and human hosts when mosquitoes feed during the night. However, malaria vectors can also feed in the early evening and in the morning when people are not protected. Here, we explored how the timing of blood feeding interacts with environmental temperature to influence the capacity of Anopheles mosquitoes to transmit the human malaria parasite Plasmodium falciparum. In laboratory experiments, we found no effect of biting time itself on the proportion of mosquitoes that became infectious (vector competence) at constant temperature. However, when mosquitoes were maintained under more realistic fluctuating temperatures, there was a significant increase in competence for mosquitoes feeding in the evening (18:00), and a significant reduction in competence for those feeding in the morning (06:00), relative to those feeding at midnight (00:00). These effects appear to be due to thermal sensitivity of malaria parasites during the initial stages of parasite development within the mosquito, and the fact that mosquitoes feeding in the evening experience cooling temperatures during the night, whereas mosquitoes feeding in the morning quickly experience warming temperatures that are inhibitory to parasite establishment. A transmission dynamics model illustrates that such differences in competence could have important implications for malaria prevalence, the extent of transmission that persists in the presence of bed nets, and the epidemiological impact of behavioural resistance. These results indicate that the interaction of temperature and feeding behaviour could be a major ecological determinant of the vectorial capacity of malaria mosquitoes.

Journal article

Saunders CN, Cota E, Baum J, Tate EWet al., 2020,

Peptide probes for Plasmodium falciparum MyoA tail interacting protein (MTIP): exploring the druggability of the malaria parasite motor complex

, ACS Chemical Biology, Vol: 15, Pages: 1313-1320, ISSN: 1554-8929

Malaria remains an endemic tropical disease, and the emergence of Plasmodium falciparum parasites resistant to current front-line medicines means that new therapeutic targets are required. The Plasmodium glideosome is a multiprotein complex thought to be essential for efficient host red blood cell invasion. At its core is a myosin motor, Myosin A (MyoA), which provides most of the force required for parasite invasion. Here, we report the design and development of improved peptide-based probes for the anchor point of MyoA, the P. falciparum MyoA tail interacting protein (PfMTIP). These probes combine low nanomolar binding affinity with significantly enhanced cell penetration and demonstrable competitive target engagement with native PfMTIP through a combination of Western blot and chemical proteomics. These results provide new insights into the potential druggability of the MTIP/MyoA interaction and a basis for the future design of inhibitors.

Journal article

Monroe A, Moore S, Okumu F, Kiware S, Lobo NF, Koenker H, Sherrard-Smith E, Gimnig J, Killeen GFet al., 2020,

Methods and indicators for measuring patterns of human exposure to malaria vectors

, Malaria Journal, Vol: 19, Pages: 1-14, ISSN: 1475-2875

BackgroundEffective targeting and evaluation of interventions that protect against adult malaria vectors requires an understanding of how gaps in personal protection arise. An improved understanding of human and mosquito behaviour, and how they overlap in time and space, is critical to estimating the impact of insecticide-treated nets (ITNs) and determining when and where supplemental personal protection tools are needed. Methods for weighting estimates of human exposure to biting Anopheles mosquitoes according to where people spend their time were first developed over half a century ago. However, crude indoor and outdoor biting rates are still commonly interpreted as indicative of human-vector contact patterns without any adjustment for human behaviour or the personal protection effects of ITNs.Main textA small number of human behavioural variables capturing the distribution of human populations indoors and outdoors, whether they are awake or asleep, and if and when they use an ITN over the course of the night, can enable a more accurate representation of human biting exposure patterns. However, to date no clear guidance is available on what data should be collected, what indicators should be reported, or how they should be calculated. This article presents an integrated perspective on relevant indicators of human-vector interactions, the critical entomological and human behavioural data elements required to quantify human-vector interactions, and recommendations for collecting and analysing such data.ConclusionsIf collected and used consistently, this information can contribute to an improved understanding of how malaria transmission persists in the context of current intervention tools, how exposure patterns may change as new vector control tools are introduced, and the potential impact and limitations of these tools. This article is intended to consolidate understanding around work on this topic to date and provide a consistent framework for building upon it. Ad

Journal article

Amulic B, Moxon C, Cunnington A, 2020,

A more granular view of neutrophils in malaria

, Trends in Parasitology, Vol: 36, Pages: 501-503, ISSN: 0169-4758

Neutrophils are abundant innate immune cells with crucial roles in immunity and vascular inflammation. Recent evidence indicates that neutrophils have a dual role in malaria, contributing to both pathogenesis and control of Plasmodium. We discuss emerging mechanisms behind these opposing functions and identify key outstanding questions.

Journal article

Llora-Batlle O, Michel-Todo L, Witmer K, Toda H, Fernandez-Becerra C, Baum J, Cortes Aet al., 2020,

Conditional expression of PfAP2-G for controlled massive sexual conversion in <i>Plasmodium falciparum</i>

, SCIENCE ADVANCES, Vol: 6, ISSN: 2375-2548

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Journal article

Suh E, Grossman M, Waite J, Dennington N, Sherrard-Smith E, Churcher T, Thomas Met al., 2020,

The influence of feeding behaviour and temperature on the capacity of mosquitoes to transmit malaria

, Nature Ecology and Evolution, ISSN: 2397-334X

Insecticide-treated bed nets reduce malaria transmission by limiting contact between mosquito vectors and human hosts when mosquitoes feed during the night. However, malaria vectors can also feed in the early evening and in the morning when people are not protected. Here, we explored how timing of blood feeding interacts with environmental temperature to influence the capacity of Anopheles mosquitoes to transmit the human malaria parasite, Plasmodium falciparum . We found no effect of biting time itself on the proportion of mosquitoes that became infectious (vector competence) at constant temperature. However, when mosquitoes were maintained under more realistic fluctuating temperatures there was a significant increase in competence for mosquitoes feeding in the evening, and a significant reduction in competence for those feeding in the morning, relative to those feeding at midnight. These effects appear to be due to thermal sensitivity of malaria parasites during the initial stages of parasite development within the mosquito, and the fact that mosquitoes feeding in the evening experience cooling temperatures during the night, whereas mosquitoes feeding in the morning quickly experience warming temperatures that are inhibitory to parasite establishment. A transmission dynamics model illustrates that such differences in competence could have important implications for disease endemicity, the extent of transmission that persists in the presence of bed nets, and the epidemiological impact of behavioural resistance. These results indicate the interaction of temperature and feeding behaviour to be a major ecological determinant of the vectorial capacity of malaria mosquitoes.

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Sherrard-Smith E, Hogan A, Hamlet A, Watson OJ, Whittaker C, Winskill P, Verity R, Lambert B, Cairns M, Okell L, Slater H, Ghani A, Walker P, Churcher T, Imperial College COVID19 response teamet al., 2020,

Report 18: The potential public health impact of COVID-19 on malaria in Africa.

The COVID-19 pandemic is likely to severely interrupt health systems in Sub-Saharan Africa (SSA) over the coming weeks and months. Approximately 90% of malaria deaths occur in this region of the world, with an estimated 380,000 deaths from malaria in 2018. Much of the gain made in malaria control over the last decade has been due to the distribution of long-lasting insecticide treated nets (LLINs). Many SSA countries planned to distribute these in 2020. We used COVID-19 and malaria transmission models to understand the likely impact that disruption to these distributions, alongside other core health services, could have on the malaria burden. Results indicate that if all malaria-control activities are highly disrupted then the malaria burden in 2020 could more than double that in the previous year, resulting in large malaria epidemics across the region. These will depend on the course of the COVID-19 epidemic and how it interrupts local health system. Our results also demonstrate that it is essential to prioritise the LLIN distributions either before or as soon as possible into local COVID-19 epidemics to mitigate this risk. Additional planning to ensure other malaria prevention activities are continued where possible, alongside planning to ensure basic access to antimalarial treatment, will further minimise the risk of substantial additional malaria mortality.

Journal article

Wilkinson MD, Lai H-E, Freemont PS, Baum Jet al., 2020,

A biosynthetic platform for antimalarial drug discovery

, Antimicrobial Agents and Chemotherapy, Vol: 64, Pages: 1-9, ISSN: 0066-4804

Advances in synthetic biology have enabled production of a variety of compounds using bacteria as a vehicle for complex compound biosynthesis. Violacein, a naturally occurring indole pigment with antibiotic properties, can be biosynthetically engineered in Escherichia coli expressing its non-native synthesis pathway. To explore whether this synthetic biosynthesis platform could be used for drug discovery, here we have screened bacterially-derived violacein against the main causative agent of human malaria, Plasmodium falciparum. We show the antiparasitic activity of bacterially-derived violacein against the P. falciparum 3D7 laboratory reference strain as well as drug-sensitive and resistant patient isolates, confirming the potential utility of this drug as an antimalarial. We then screen a biosynthetic series of violacein derivatives against P. falciparum growth. The demonstrated varied activity of each derivative against asexual parasite growth points to potential for further development of violacein as an antimalarial. Towards defining its mode of action, we show that biosynthetic violacein affects the parasite actin cytoskeleton, resulting in an accumulation of actin signal that is independent of actin polymerization. This activity points to a target that modulates actin behaviour in the cell either in terms of its regulation or its folding. More broadly, our data show that bacterial synthetic biosynthesis could become a suitable platform for antimalarial drug discovery with potential applications in future high-throughput drug screening with otherwise chemically-intractable natural products.

Journal article

Rueda-Zubiaurre A, Yahiya S, Fischer O, Hu X, Saunders C, Sharma S, Straschil U, Shen J, Tate EW, Delves M, Baum J, Barnard A, Fuchter MJet al., 2020,

Structure-activity relationship studies of a novel class of transmission blocking antimalarials targeting male gametes.

, Journal of Medicinal Chemistry, Vol: 63, Pages: 2240-2262, ISSN: 0022-2623

Malaria is still a leading cause of mortality among children in the developing world, and despite the immense progress made in reducing the global burden, further efforts are needed if eradication is to be achieved. In this context, targeting transmission is widely recognized as a necessary intervention towards that goal. After carrying out a screen to discover new transmission-blocking agents, herein we report our medicinal chemistry efforts to study the potential of the most robust hit, DDD01035881, as a male-gamete targeted compound. We reveal key structural features for the activity of this series and identify analogues with greater potency and improved metabolic stability. We believe this study lays the groundwork for further development of this series as a transmission blocking agent.

Journal article

Okell L, Bretscher MT, Dahal P, Griffin J, stepniewska K, Bassat Q, Baudin E, D'Alessandro U, Djimde A, Dorsey G, Espie E, Fofana B, Gonzalez R, Juma E, Karema C, Lasry E, Lell B, Lima N, Menendez C, Mombo-Ngoma G, Moreira C, Nikiema F, Ouedraogo J, Staedke S, Tinto H, Valea I, Yeka A, Ghani A, Guerin Pet al., 2020,

The duration of chemoprophylaxis against malaria after treatment with artesunate-amodiaquine and artemether-lumefantrine and the effects of pfmdr1 86Y and pfcrt 76T: a meta-analysis of individual patient data

, BMC Medicine, Vol: 18, Pages: 1-17, ISSN: 1741-7015

Background: The majority of Plasmodium falciparum malaria cases in Africa are treated with the artemisinin combination therapies artemether-lumefantrine (AL) and artesunate-amodiaquine (AS-AQ), with amodiaquine being also widely used as part of seasonal malaria chemoprevention programmes combined with sulfadoxine-pyrimethamine. Whilst artemisinin derivatives have a short half-life, lumefantrine and amodiaquine may give rise to differing durations of post-treatment prophylaxis, an important additional benefit to patients in higher transmission areas. Methods: We analyzed individual patient data from 8 clinical trials of AL versus AS-AQ in 12 sites in Africa (n=4214 individuals). The time to PCR-confirmed re-infection after treatment was used to estimate the duration of post-treatment protection, accounting for variation in transmission intensity between settings using hidden semi-Markov models. Accelerated failure-time models were used to identify potential effects of covariates on the time to re-infection. The estimated duration of chemoprophylaxis was then used in a mathematical model of malaria transmission to determine the potential public health impact of each drug when used for first-line treatment. Results: We estimated a mean duration of post-treatment protection of 13.0 days (95% CI 10.7-15.7) for AL and 15.2 days (95% CI 12.8-18.4) for AS-AQ overall. However, the duration varied significantly between trial sites, from 8.7-18.6 days for AL and 10.2-18.7 days for AS-AQ. Significant predictors of time to re-infection in multivariate models were transmission intensity, age, drug, and parasite genotype. Where wild type pfmdr1 and pfcrt parasite genotypes predominated (<=20% 86Y and 76T mutants, respectively), AS-AQ provided ~2-fold longer protection than AL. Conversely at a higher prevalence of 86Y and 76T mutant parasites (>80%), AL provided up to 1.5-fold longer protection than AS-AQ. Our simulations found that these differences in the duration of protec

Journal article

Suen HM, Pasvol G, Cunnington A, 2020,

Clinical and laboratory features associated with serum phosphate concentrations in malaria and other febrile illnesses

, Malaria Journal, Vol: 19, ISSN: 1475-2875

BackgroundHypophosphatemia is common in severe infections including malaria. Previous studies suggested that serum phosphate concentrations correlate with temperature, but it is unclear whether the type of infection and other factors occurring during infection influence this association. Here relationships were investigated between serum phosphate levels, cause of fever, demographic, clinical and laboratory parameters.MethodsAnonymized data were analysed from 633 adults with malaria or other febrile illness admitted to Northwick Park Hospital, London, UK. Univariable and multivariable generalized linear model analyses were performed to examine associations with serum phosphate levels. Interaction terms were included to investigate whether cause of fever (malaria vs other illness), malaria parasite species, or malaria severity influenced the association of other variables with phosphate.ResultsHypophosphatemia was common in subjects with malaria (211/542 (39%)), and in other febrile illnesses (24/91 (26%)), however median phosphate levels did not differ significantly by diagnostic group, parasite species or severity of malaria. In all analyses, there were highly significant negative associations between serum phosphate and axillary temperature, and positive associations between serum phosphate and platelet count. There were no significant interactions between these variables and cause of fever, parasite species or severity of illness. Sodium and potassium concentrations were associated with serum phosphate in subjects with malaria and when data from all subjects was combined.ConclusionSerum phosphate is consistently associated with temperature and platelet count in adults with diverse causes of fever. This may be a consequence of phosphate shifts from plasma into cells to support ATP generation for thermogenesis and platelet activation.

Journal article

Patel H, Dunican C, Cunnington A, 2020,

Predictors of outcome in childhood Plasmodium falciparum malaria

, Virulence, Vol: 11, Pages: 199-221, ISSN: 2150-5594

Plasmodium falciparum malaria is classified as either uncomplicated or severe, determining clinical management and providing a framework for understanding pathogenesis. Severe malaria in children is defined by the presence of one or more features associated with adverse outcome, but there is wide variation in the predictive value of these features. Here we review the evidence for the usefulness of these features, alone and in combination, to predict death and other adverse outcomes, and we consider the role that molecular biomarkers may play in augmenting this prediction. We also examine whether a more personalized approach to predicting outcome for specific presenting syndromes of severe malaria, particularly cerebral malaria, has the potential to be more accurate. We note a general need for better external validation in studies of outcome predictors and for the demonstration that predictors can be used to guide clinical management in a way that improves survival and long-term health.

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