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  1. Article ; Online: Quantifying individual variability in exposure risk to mosquito bites in the Cascades region, Burkina Faso

    Federica Guglielmo / Antoine Sanou / Thomas Churcher / Heather M. Ferguson / Hilary Ranson / Ellie Sherrard-Smith

    Malaria Journal, Vol 20, Iss 1, Pp 1-

    2021  Volume 14

    Abstract: Abstract Background The 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 ... ...

    Abstract Abstract Background The 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. Methods 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 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). Results Substantial 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. Conclusion This 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 control.
    Keywords Arctic medicine. Tropical medicine ; RC955-962 ; Infectious and parasitic diseases ; RC109-216
    Language English
    Publishing date 2021-01-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: The potential impact of Anopheles stephensi establishment on the transmission of Plasmodium falciparum in Ethiopia and prospective control measures

    Arran Hamlet / Dereje Dengela / J. Eric Tongren / Fitsum G. Tadesse / Teun Bousema / Marianne Sinka / Aklilu Seyoum / Seth R. Irish / Jennifer S. Armistead / Thomas Churcher

    BMC Medicine, Vol 20, Iss 1, Pp 1-

    2022  Volume 10

    Abstract: Abstract Background Sub-Saharan Africa has seen substantial reductions in cases and deaths due to malaria over the past two decades. While this reduction is primarily due to an increasing expansion of interventions, urbanisation has played its part as ... ...

    Abstract Abstract Background Sub-Saharan Africa has seen substantial reductions in cases and deaths due to malaria over the past two decades. While this reduction is primarily due to an increasing expansion of interventions, urbanisation has played its part as urban areas typically experience substantially less malaria transmission than rural areas. However, this may be partially lost with the invasion and establishment of Anopheles stephensi. A. stephensi, the primary urban malaria vector in Asia, was first detected in Africa in 2012 in Djibouti and was subsequently identified in Ethiopia in 2016, and later in Sudan and Somalia. In Djibouti, malaria cases have increased 30-fold from 2012 to 2019 though the impact in the wider region remains unclear. Methods Here, we have adapted an existing model of mechanistic malaria transmission to estimate the increase in vector density required to explain the trends in malaria cases seen in Djibouti. To account for the observed plasticity in An. stephensi behaviour, and the unknowns of how it will establish in a novel environment, we sample behavioural parameters in order to account for a wide range of uncertainty. This quantification is then applied to Ethiopia, considering temperature-dependent extrinsic incubation periods, pre-existing vector-control interventions and Plasmodium falciparum prevalence in order to assess the potential impact of An. stephensi establishment on P. falciparum transmission. Following this, we estimate the potential impact of scaling up ITN (insecticide-treated nets)/IRS (indoor residual spraying) and implementing piperonyl butoxide (PBO) ITNs and larval source management, as well as their economic costs. Results We estimate that annual P. falciparum malaria cases could increase by 50% (95% CI 14–90) if no additional interventions are implemented. The implementation of sufficient control measures to reduce malaria transmission to pre-stephensi levels will cost hundreds of millions of USD. Conclusions Substantial heterogeneity across the country is predicted and large increases in vector control interventions could be needed to prevent a major public health emergency.
    Keywords Anopheles stephensi ; Malaria ; Mathematical modelling ; Ethiopia ; Insecticide ; Invasive ; Medicine ; R
    Language English
    Publishing date 2022-04-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Partial indoor residual spraying with pirimiphos-methyl as an effective and cost-saving measure for the control of Anopheles gambiae s.l. in northern Ghana.

    Coleman, Sylvester / Yihdego, Yemane / Sherrard-Smith, Ellie / Thomas, Churcher S / Dengela, Dereje / Oxborough, Richard M / Dadzie, Samuel K / Boakye, Daniel / Gyamfi, Frank / Obiri-Danso, Kwasi / Johns, Ben / Siems, Lilly V / Lucas, Bradford / Tongren, Jon Eric / Zigirumugabe, Sixte / Dery, Dominic / Fornadel, Christen / George, Kristen / Belemvire, Allison /
    Carlson, Jenny / Irish, Seth R / Armistead, Jennifer S / Seyoum, Aklilu

    Scientific reports

    2021  Volume 11, Issue 1, Page(s) 18055

    Abstract: The scale up of indoor residual spraying (IRS) and insecticide treated nets have contributed significantly to global reductions in malaria prevalence over the last two decades. However, widespread pyrethroid resistance has necessitated the use of new and  ...

    Abstract The scale up of indoor residual spraying (IRS) and insecticide treated nets have contributed significantly to global reductions in malaria prevalence over the last two decades. However, widespread pyrethroid resistance has necessitated the use of new and more expensive insecticides for IRS. Partial IRS with pirimiphos-methyl in experimental huts and houses in a village-wide trial was evaluated against Anopheles gambiae s.l. in northern Ghana. Four different scenarios in which either only the top or bottom half of the walls of experimental huts were sprayed, with or without also spraying the ceiling were compared. Mortality of An. gambiae s.l. on partially sprayed walls was compared with the standard procedures in which all walls and ceiling surfaces are sprayed. A small-scale trial was then conducted to assess the effectiveness, feasibility, and cost of spraying only the upper walls and ceiling as compared to full IRS and no spraying in northern Ghana. Human landing catches were conducted to estimate entomological indices and determine the effectiveness of partial IRS. An established transmission dynamics model was parameterized by an analysis of the experimental hut data and used to predict the epidemiological impact and cost effectiveness of partial IRS for malaria control in northern Ghana. In the experimental huts, partial IRS of the top (IRR 0.89, p = 0.13) or bottom (IRR 0.90, p = 0.15) half of walls and the ceiling was not significantly less effective than full IRS in terms of mosquito mortality. In the village trial, the annual entomological inoculation rate was higher for the unsprayed control (217 infective bites/person/year (ib/p/yr)) compared with the fully and partially sprayed sites, with 28 and 38 ib/p/yr, respectively. The transmission model predicts that the efficacy of partial IRS against all-age prevalence of malaria after six months would be broadly equivalent to a full IRS campaign in which 40% reduction is expected relative to no spray campaign. At scale, partial IRS in northern Ghana would have resulted in a 33% cost savings ($496,426) that would enable spraying of 36,000 additional rooms. These findings suggest that partial IRS is an effective, feasible, and cost saving approach to IRS that could be adopted to sustain and expand implementation of this key malaria control intervention.
    MeSH term(s) Aerosolized Particles and Droplets ; Animals ; Anopheles/drug effects ; Cost-Benefit Analysis ; Geography ; Ghana/epidemiology ; Insecticides/administration & dosage ; Malaria/epidemiology ; Malaria/prevention & control ; Malaria/transmission ; Models, Theoretical ; Mosquito Control/methods ; Organothiophosphorus Compounds/administration & dosage ; Public Health Surveillance
    Chemical Substances Aerosolized Particles and Droplets ; Insecticides ; Organothiophosphorus Compounds ; pirimiphos methyl (29232-93-7)
    Language English
    Publishing date 2021-09-10
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-021-97138-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Design and methods for a quasi-experimental pilot study to evaluate the impact of dual active ingredient insecticide-treated nets on malaria burden in five regions in sub-Saharan Africa

    Adama Gansané / Baltazar Candrinho / Aimable Mbituyumuremyi / Perpetua Uhomoibhi / Sagnon NFalé / Audu Bala Mohammed / Wamdaogo Moussa Guelbeogo / Antoine Sanou / David Kangoye / Siaka Debe / Moubassira Kagone / Emmanuel Hakizimana / Aline Uwimana / Albert Tuyishime / Chantal M. Ingabire / Joseph H. Singirankabo / Hannah Koenker / Dulcisaria Marrenjo / Ana Paula Abilio /
    Crizologo Salvador / Binete Savaio / Okefu Oyale Okoko / Ibrahim Maikore / Emmanuel Obi / Samson Taiwo Awolola / Adedapo Adeogun / Dele Babarinde / Onoja Ali / Federica Guglielmo / Joshua Yukich / Sara Scates / Ellie Sherrard-Smith / Thomas Churcher / Christen Fornadel / Jenny Shannon / Nami Kawakyu / Emily Beylerian / Peder Digre / Kenzie Tynuv / Christelle Gogue / Julia Mwesigwa / Joseph Wagman / Monsuru Adeleke / Ande Taiwo Adeolu / Molly Robertson

    Malaria Journal, Vol 21, Iss 1, Pp 1-

    2022  Volume 20

    Abstract: Abstract Background Vector control tools have contributed significantly to a reduction in malaria burden since 2000, primarily through insecticidal-treated bed nets (ITNs) and indoor residual spraying. In the face of increasing insecticide resistance in ... ...

    Abstract Abstract Background Vector control tools have contributed significantly to a reduction in malaria burden since 2000, primarily through insecticidal-treated bed nets (ITNs) and indoor residual spraying. In the face of increasing insecticide resistance in key malaria vector species, global progress in malaria control has stalled. Innovative tools, such as dual active ingredient (dual-AI) ITNs that are effective at killing insecticide-resistant mosquitoes have recently been introduced. However, large-scale uptake has been slow for several reasons, including higher costs and limited evidence on their incremental effectiveness and cost-effectiveness. The present report describes the design of several observational studies aimed to determine the effectiveness and cost-effectiveness of dual-AI ITNs, compared to standard pyrethroid-only ITNs, at reducing malaria transmission across a variety of transmission settings. Methods Observational pilot studies are ongoing in Burkina Faso, Mozambique, Nigeria, and Rwanda, leveraging dual-AI ITN rollouts nested within the 2019 and 2020 mass distribution campaigns in each country. Enhanced surveillance occurring in select study districts include annual cross-sectional surveys during peak transmission seasons, monthly entomological surveillance, passive case detection using routine health facility surveillance systems, and studies on human behaviour and ITN use patterns. Data will compare changes in malaria transmission and disease burden in districts receiving dual-AI ITNs to similar districts receiving standard pyrethroid-only ITNs over three years. The costs of net distribution will be calculated using the provider perspective including financial and economic costs, and a cost-effectiveness analysis will assess incremental cost-effectiveness ratios for Interceptor® G2, Royal Guard®, and piperonyl butoxide ITNs in comparison to standard pyrethroid-only ITNs, based on incidence rate ratios calculated from routine data. Conclusions Evidence of the effectiveness and ...
    Keywords Malaria ; Vector control ; Dual-AI ITNs ; Burkina Faso ; Mozambique ; Nigeria ; Arctic medicine. Tropical medicine ; RC955-962 ; Infectious and parasitic diseases ; RC109-216
    Subject code 360
    Language English
    Publishing date 2022-01-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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