Publications
135 results found
Gatton ML, Chitnis N, Churcher T, et al., 2013, THE IMPORTANCE OF MOSQUITO BEHAVIOURAL ADAPTATIONS TO MALARIA CONTROL IN AFRICA, Evolution, Vol: 67, Pages: 1218-1230, ISSN: 0014-3820
Over the past decade the use of long-lasting insecticidal nets (LLINs), in combination with improved drug therapies, indoor residual spraying (IRS), and better health infrastructure, has helped reduce malaria in many African countries for the first time in a generation. However, insecticide resistance in the vector is an evolving threat to these gains. We review emerging and historical data on behavioral resistance in response to LLINs and IRS. Overall the current literature suggests behavioral and species changes may be emerging, but the data are sparse and, at times unconvincing. However, preliminary modeling has demonstrated that behavioral resistance could have significant impacts on the effectiveness of malaria control. We propose seven recommendations to improve understanding of resistance in malaria vectors. Determining the public health impact of physiological and behavioral insecticide resistance is an urgent priority if we are to maintain the significant gains made in reducing malaria morbidity and mortality.
Turner HC, Churcher TS, Walker M, et al., 2013, Uncertainty Surrounding Projections of the Long-Term Impact of Ivermectin Treatment on Human Onchocerciasis, PLOS NEGLECTED TROPICAL DISEASES, Vol: 7, ISSN: 1935-2735
- Author Web Link
- Open Access Link
- Cite
- Citations: 41
Pollitt LC, Churcher TS, Dawes EJ, et al., 2013, Costs of crowding for the transmission of malaria parasites, Evolutionary Applications, Pages: n/a-n/a, ISSN: 1752-4571
Bousema T, Churcher TS, Morlais I, et al., 2013, Can field-based mosquito feeding assays be used for evaluating transmission-blocking interventions?, TRENDS IN PARASITOLOGY, Vol: 29, Pages: 53-59, ISSN: 1471-4922
- Author Web Link
- Cite
- Citations: 43
, 2013, Correction: Modulation of Malaria Infection in Anopheles gambiae Mosquitoes Exposed to Natural Midgut Bacteria, PloS one, Vol: 8, ISSN: 1932-6203
Churcher TS, Blagborough AM, Sinden RE, 2012, Measuring the blockade of malaria transmission: analyzing the results of mosquito feeding assays, Malaria Journal, Vol: 11
Bousema T, Dinglasan RR, Morlais I, et al., 2012, Mosquito Feeding Assays to Determine the Infectiousness of Naturally Infected <i>Plasmodium falciparum</i> Gametocyte Carriers, PLOS ONE, Vol: 7, ISSN: 1932-6203
- Author Web Link
- Cite
- Citations: 137
Basáñez M-G, McCarthy JS, French MD, et al., 2012, A Research Agenda for Helminth Diseases of Humans: Modelling for Control and Elimination, PLoS Neglected Tropical Diseases
Basanez M-G, McCarthy JS, French MD, et al., 2012, A Research Agenda for Helminth Diseases of Humans: Modelling for Control and Elimination, PLOS Neglected Tropical Diseases, Vol: 6, ISSN: 1935-2735
Human helminthiases are of considerable publichealth importance in sub-Saharan Africa, Asia, and LatinAmerica. The acknowledgement of the disease burden dueto helminth infections, the availability of donated oraffordable drugs that are mostly safe and moderatelyefficacious, and the implementation of viable mass drugadministration (MDA) interventions have prompted theestablishment of various large-scale control and eliminationprogrammes. These programmes have benefited fromimproved epidemiological mapping of the infections, betterunderstanding of the scope and limitations of currentlyavailable diagnostics and of the relationship betweeninfection and morbidity, feasibility of community-directedor school-based interventions, and advances in the design ofmonitoring and evaluation (M&E) protocols. Considerablesuccess has been achieved in reducing morbidity orsuppressing transmission in a number of settings, whilstchallenges remain in many others. Some of the obstaclesinclude the lack of diagnostic tools appropriate to thechanging requirements of ongoing interventions andelimination settings; the reliance on a handful of drugsabout which not enough is known regarding modes ofaction, modes of resistance, and optimal dosage singly or incombination; the difficulties in sustaining adequate coverageand compliance in prolonged and/or integrated programmes;an incomplete understanding of the social,behavioural, and environmental determinants of infection;and last, but not least, very little investment in research anddevelopment (R&D). The Disease Reference Group onHelminth Infections (DRG4), established in 2009 by theSpecial Programme for Research and Training in TropicalDiseases (TDR), was given the mandate to undertake acomprehensive review of recent advances in helminthiasesresearch, identify research gaps, and rank priorities for anR&D agenda for the control and elimination of theseinfections. This review presents the processes undertakento identify and rank ten t
Basanez M-G, French MD, Walker M, et al., 2012, Paradigm lost: how parasite control may alter pattern and process in human helminthiases, TRENDS IN PARASITOLOGY, Vol: 28, Pages: 161-171, ISSN: 1471-4922
- Author Web Link
- Cite
- Citations: 23
Bousema R, 2012, Hitting Hotspots: Spatial Targeting of Malaria for Control and Elimination, PLoS Med, Vol: 9, Pages: e1001165-e1001165
<p>Teun Bousema and colleagues argue that targeting malaria “hotspots” is a highly efficient way to reduce malaria transmission at all levels of transmission intensity.</p>
Harris C, Morlais I, Churcher TS, et al., 2012, <i>Plasmodium falciparum</i> Produce Lower Infection Intensities in Local <i>versus</i> Foreign <i>Anopheles gambiae</i> Populations, PLOS ONE, Vol: 7, ISSN: 1932-6203
- Author Web Link
- Cite
- Citations: 38
Churcher TS, Blagborough AM, Delves M, et al., 2012, Measuring the blockade of malaria transmission - an analysis of the standard membrane feeding assay, Int J Parasitol, Vol: 42, Pages: 1037-1044
The Standard Membrane Feeding Assay (SMFA) is currently considered to be the 'gold standard' for assessing the effectiveness of malaria transmission blocking interventions (TBIs) in vivo. The operation and analysis of SMFAs has varied between laboratories: field scientists often measure TBI efficacy as a reduction in the prevalence of infected mosquitoes whilst laboratory scientists are more likely to quote efficacy as a change in the number of oocysts within the mosquito. These metrics give outputs that differ widely, resulting in a need for greater understanding of how the SMFA informs TBI assessment. Using data from 536 different assays (conducted on Plasmodium falciparum and Plasmodiumberghei, in either Anopheles gambiae or Anopheles stephensi) it is shown that the relationship between these metrics is complex, yet predictable. Results demonstrate that the distribution of oocysts between mosquitoes is highly aggregated, making efficacy estimates based on reductions in intensity highly uncertain. Analysis of 30 SMFAs carried out on the same TBI confirms that the observed reduction in prevalence depends upon the parasite exposure (as measured by oocyst intensity in the control group), with assays which have lower exposure appearing more effective. By contrast, if efficacy is estimated as a reduction in oocyst intensity, then this candidate demonstrated constant efficacy, irrespective of the exposure level. To report transmission-blockade efficacy accurately, the results of SMFAs should give both the prevalence and intensity of oocysts in both the control and intervention group. Candidates should be assessed against a range of parasite exposures to allow laboratory results to be extrapolated to different field situations. Currently, many studies assessing TBIs are underpowered and uncertainties in efficacy estimates rarely reported. Statistical techniques that account for oocyst over-dispersion can reduce the number of mosquitoes that need to be dissected and allow
Sinden RE, Blagborough AM, Churcher T, et al., 2012, The design and interpretation of laboratory assays measuring mosquito transmission of Plasmodium., Trends in Parasitology
Since 2010 two global reviews of malaria research have recognized that local elimination and eradication of Plasmodium parasites are key drivers for further experimentation. To achieve these ambitious objectives it is universally recognized we must reduce malaria transmission through the mosquito vectors. A plethora of new laboratory assays are being developed to interrogate malaria transmission from the gametocyte to the sporozoite stage: assays that augment well-established field protocols to determine the entomological inoculation rate. However, the diverse readouts of these assays are not directly comparable. Here we attempt to identify the utility of each assay and provide rational frameworks by which to compare the impacts recorded by the diverse methodologies.
Solomon AW, Engels D, Bailey RL, et al., 2012, A Diagnostics Platform for the Integrated Mapping, Monitoring and Surveillance of Neglected Tropical Diseases: Rationale and Target Product Profiles, PLoS Neglected Tropical Diseases
White MT, Griffin JT, Churcher TS, et al., 2011, Modelling the impact of vector control interventions on Anopheles gambiae population dynamics, Parasites & Vectors, Vol: 4, ISSN: 1756-3305
BACKGROUND:Intensive anti-malaria campaigns targeting the Anopheles population have demonstrated substantial reductions in adult mosquito density. Understanding the population dynamics of Anopheles mosquitoes throughout their whole lifecycle is important to assess the likely impact of vector control interventions alone and in combination as well as to aid the design of novel interventions.METHODS:An ecological model of Anopheles gambiae sensu lato populations incorporating a rainfall-dependent carrying capacity and density-dependent regulation of mosquito larvae in breeding sites is developed. The model is fitted to adult mosquito catch and rainfall data from 8 villages in the Garki District of Nigeria (the 'Garki Project') using Bayesian Markov Chain Monte Carlo methods and prior estimates of parameters derived from the literature. The model is used to compare the impact of vector control interventions directed against adult mosquito stages--long-lasting insecticide treated nets (LLIN), indoor residual spraying (IRS)-- and directed against aquatic mosquito stages, alone and in combination on adult mosquito density.RESULTS:A model in which density-dependent regulation occurs in the larval stages via a linear association between larval density and larval death rates provided a good fit to seasonal adult mosquito catches. The effective mosquito reproduction number in the presence of density-dependent regulation is dependent on seasonal rainfall patterns and peaks at the start of the rainy season. In addition to killing adult mosquitoes during the extrinsic incubation period, LLINs and IRS also result in less eggs being oviposited in breeding sites leading to further reductions in adult mosquito density. Combining interventions such as the application of larvicidal or pupacidal agents that target the aquatic stages of the mosquito lifecycle with LLINs or IRS can lead to substantial reductions in adult mosquito density.CONCLUSIONS:Density-dependent regulation of anophel
Okell LC, Griffin JT, Kleinschmidt I, et al., 2011, The Potential Contribution of Mass Treatment to the Control of <i>Plasmodium falciparum</i> Malaria, PLOS ONE, Vol: 6, ISSN: 1932-6203
- Author Web Link
- Open Access Link
- Cite
- Citations: 103
Bousema T, Sutherland CJ, Churcher TS, et al., 2011, Human immune responses that reduce the transmission of Plasmodium falciparum in African populations, INTERNATIONAL JOURNAL FOR PARASITOLOGY, Vol: 41, Pages: 293-300, ISSN: 0020-7519
- Author Web Link
- Cite
- Citations: 48
Churcher TS, Dawes EJ, Sinden RE, et al., 2010, Population biology of malaria within the mosquito: density-dependent processes and potential implications for transmission-blocking interventions, MALARIA JOURNAL, Vol: 9, ISSN: 1475-2875
- Author Web Link
- Open Access Link
- Cite
- Citations: 27
French MD, Churcher TS, Gambhir M, et al., 2010, Observed Reductions in <i>Schistosoma mansoni</i> Transmission from Large-Scale Administration of Praziquantel in Uganda: A Mathematical Modelling Study, PLOS NEGLECTED TROPICAL DISEASES, Vol: 4, ISSN: 1935-2735
- Author Web Link
- Open Access Link
- Cite
- Citations: 62
Harris C, Morlais I, Churcher TS, et al., 2010, SYMPATRIC <i>PLASMODIUM FALCIPARUM-ANOPHELES GAMBIAE</i> POPULATIONS PRODUCE LOWER INFECTION INTENSITIES IN AFRICA, 59th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 386-386, ISSN: 0002-9637
Griffin JT, Hollingsworth D, Okell LC, et al., 2010, STRATEGIES TOWARDS <i>PLASMODIUM FALCIPARUM</i> MALARIA ELIMINATION IN AFRICA USING CURRENTLY AVAILABLE TOOLS, 59th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 262-262, ISSN: 0002-9637
Churcher TS, Bousema TJ, Drakeley CJ, et al., 2010, LOW GAMETOCYTE DENSITIES RESTRICT THE DEVELOPMENT OF <i>PLASMODIUM FALCIPARUM</i> WITHIN <i>ANOPHELES GAMBIAE</i> WITH IMPLICATIONS FOR THE HUMAN RESERVOIR OF INFECTION AND PARASITE ELIMINATION, 59th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 169-169, ISSN: 0002-9637
Griffin JT, Hollingsworth TD, Okell LC, et al., 2010, Reducing Plasmodium falciparum malaria transmission in Africa: a model-based evaluation of intervention strategies., PLoS Med, Vol: 7, Pages: 1-27, ISSN: 1549-1676
BACKGROUND: Over the past decade malaria intervention coverage has been scaled up across Africa. However, it remains unclear what overall reduction in transmission is achievable using currently available tools. METHODS AND FINDINGS: We developed an individual-based simulation model for Plasmodium falciparum transmission in an African context incorporating the three major vector species (Anopheles gambiae s.s., An. arabiensis, and An. funestus) with parameters obtained by fitting to parasite prevalence data from 34 transmission settings across Africa. We incorporated the effect of the switch to artemisinin-combination therapy (ACT) and increasing coverage of long-lasting insecticide treated nets (LLINs) from the year 2000 onwards. We then explored the impact on transmission of continued roll-out of LLINs, additional rounds of indoor residual spraying (IRS), mass screening and treatment (MSAT), and a future RTS,S/AS01 vaccine in six representative settings with varying transmission intensity (as summarized by the annual entomological inoculation rate, EIR: 1 setting with low, 3 with moderate, and 2 with high EIRs), vector-species combinations, and patterns of seasonality. In all settings we considered a realistic target of 80% coverage of interventions. In the low-transmission setting (EIR approximately 3 ibppy [infectious bites per person per year]), LLINs have the potential to reduce malaria transmission to low levels (<1% parasite prevalence in all age-groups) provided usage levels are high and sustained. In two of the moderate-transmission settings (EIR approximately 43 and 81 ibppy), additional rounds of IRS with DDT coupled with MSAT could drive parasite prevalence below a 1% threshold. However, in the third (EIR = 46) with An. arabiensis prevailing, these interventions are insufficient to reach this threshold. In both high-transmission settings (EIR approximately 586 and 675 ibppy), either unrealistically high coverage levels (>90%) or novel tools and/or
Churcher TS, Kaplan RM, Ardelli BF, et al., 2010, Mass Treatment of Parasitic Disease: Implications forthe Development and Spread of AnthelminticResistance, Antimicrobial Resistance – Beyond the Breakpoint, Editors: Todd Weber, Publisher: Basel, Karger
There has been a dramatic increase in the use of mass drug administration to reduce the morbidity associated with helminth infections of humans, raising the likelihood that anthelmintic resistance may become a public health concern of the future. After highlighting the scope and magnitude of the chemotherapy-based helminth control programs presently in place, this chapter emphasizes the mechanisms of action of the main anthelmintic drugs in use and how resistance may develop. To date, the most established population-based mass drug administration campaigns have been against the filarial parasites which cause human onchocerciasis and lymphatic filariasis. The molecular and parasitological evidence suggesting the presence of drug resistance in human filarial parasites is reviewed and factors influencing the spread of drug resistant parasites are discussed, taking examples from veterinary helminths and the use of mathematical models. In particular, the public health impact of the development of resistance by soil-transmitted helminths, such as hookworm, is a real concern. Implications of the development of anthelmintic resistance are discussed in relation to existing control programs, emphasizing how their monitoring and evaluation is essential to prevent it becoming a major public health concern of the future.
Churcher TS, Kaplan RM, Ardelli BF, et al., 2010, Mass Treatment of Parasitic Disease: Implications for the Development and Spread of Anthelmintic Resistance, Basel, Publisher: Karger Publishers, ISBN: 9783805593236
There has been a dramatic increase in the use of mass drug administration to reduce the morbidity associated with helminth infections of humans, raising the likelihood that anthelmintic resistance may become a public health concern of the future. After highlighting the scope and magnitude of the chemotherapy-based helminth control programs presently in place, this chapter emphasizes the mechanisms of action of the main anthelmintic drugs in use and how resistance may develop. To date, the most established population-based mass drug administration campaigns have been against the filarial parasites which cause human on chocerciasis and lymphatic filariasis. The molecular and parasitological evidence suggesting the presence of drug resistance in human filarial parasites is reviewed and factors influencing the spread of drug resistant parasites are discussed, taking examples from veterinary helminths and the use of mathematical models. In particular, the public health impact of the development of resistance by soil-transmitted helminths, such as hookworm, is a real concern. Implications of the development of anthelmintic resistance are discussed in relation to existing control programs, emphasizing how their monitoring and evaluation is essential to prevent it becoming a major public health concern of the future.
Dawes EJ, Churcher TS, Zhuang S, et al., 2009, Anopheles mortality is both age- and <i>Plasmodium</i>-density dependent: implications for malaria transmission, MALARIA JOURNAL, Vol: 8
- Author Web Link
- Open Access Link
- Cite
- Citations: 80
Churcher TS, Pion SDS, Osei-Atweneboana MY, et al., 2009, Identifying sub-optimal responses to ivermectin in the treatment of River Blindness, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 106, Pages: 16716-16721, ISSN: 0027-8424
- Author Web Link
- Cite
- Citations: 68
Taylor MJ, Awadzi K, Basanez M-G, et al., 2009, Onchocerciasis Control: Vision for the Future from a Ghanian perspective, PARASITES & VECTORS, Vol: 2, ISSN: 1756-3305
- Author Web Link
- Open Access Link
- Cite
- Citations: 41
Churcher TS, Basanez M-G, 2009, Sampling strategies to detect anthelmintic resistance: the perspective of human onchocerciasis, TRENDS IN PARASITOLOGY, Vol: 25, Pages: 11-17, ISSN: 1471-4922
- Author Web Link
- Cite
- Citations: 23
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.