Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Omgaan met mogelijke overlast van stekende insecten in en rondom de natuurgebieden Punthuizen, Stroothuizen en Beuninger Achterveld
    Verdonschot, Piet F.M. - \ 2017
    Wageningen : Wageningen Environmental Research, Zoetwaterecosystemen - ISBN 9789463436175 - 28
    culicidae - insecten - steken - natuurgebieden - overijssel - culicidae - insects - stings - natural areas - overijssel
    Microorganism-mediated behaviour of malaria mosquitoes
    Busula, Annette O. - \ 2017
    Wageningen University. Promotor(en): W. Takken, co-promotor(en): J. de Boer. - Wageningen : Wageningen University - ISBN 9789463431156 - 199
    culicidae - anopheles gambiae - anopheles arabiensis - mosquito-borne diseases - disease vectors - animal behaviour - host-seeking behaviour - plasmodium falciparum - hosts - man - cows - hens - odours - culicidae - anopheles gambiae - anopheles arabiensis - ziekten overgebracht door muskieten - vectoren, ziekten - diergedrag - gedrag bij zoeken van een gastheer - plasmodium falciparum - gastheren (dieren, mensen, planten) - mens - koeien - hennen - geurstoffen

    Host-seeking is an important component of mosquito vectorial capacity on which the success of the other behavioural determinants depends. Blood-seeking mosquitoes are mainly guided by chemical cues released by their blood hosts. This thesis describes results of a study that determined the effect of microorganisms – host skin bacteria as well as malaria parasites – on host-seeking behaviour of female Anopheles gambiae sensu stricto and An. arabiensis in Homabay county, western Kenya. Semi-field and field experiments were conducted to determine the response of mosquitoes with different host preference to synthetic and natural odour blends from three vertebrate hosts, a human, a cow and a chicken. Screen house experiments were conducted to test whether specific skin bacteria or a mix of skin bacterial volatiles from the three vertebrate hosts mediate mosquito response. A review chapter in this thesis discusses how malaria parasites can manipulate human hosts to enhance their own transmission, by making the hosts more attractive to mosquitoes. Another experiment, using a dual-choice olfactometer, determined whether infection with malaria parasites increases human attractiveness to malaria mosquitoes, and whether the attractiveness of infected humans is Plasmodium falciparum-stage specific. Here, the same children participated in the study during infection with malaria parasites and after treatment with antimalarial drugs, artemisinin lumefantrine. Cage assays were further used to test mechanisms of attractiveness of P. falciparum-infected individuals using body odours or skin bacterial volatiles collected from the children at the two time points. Overall results show that skin bacterial volatiles play an important role in guiding mosquitoes with different host preferences to their specific host. For An. gambiae s.s., high (microscopic) densities of P. falciparum gametocytes (and not parasite-free, submicroscopic gametocytes or asexual stages of Plasmodium parasites) results into higher attractiveness of hosts, and body odours play a role in attractiveness of P. falciparum-infected humans. The results may help to develop more effective health policies and enable targeted interventions towards the most attractive hosts, which could contribute to reductions in malaria transmission. Identification of general or common attractive volatiles produced by the natural hosts as well as those from the gametocyte carriers may contribute to the development of an improved synthetic odour blend that may be used for sampling of mosquitoes with different host preferences. The use of powerful attractive odorants may result in reductions of vector-borne diseases transmitted by mosquitoes.

    Stekende insecten rondom de Groote Peel : nulmeting 2016
    Verdonschot, Piet F.M. ; Dekkers, Dorine D. - \ 2017
    Wageningen : Wageningen Environmental Research (Alterra), Zoetwatersystemen (Notitie / Zoetwaterecosystemen, Wageningen Environmental Research ) - ISBN 9789463431231 - 40
    culicidae - steken (activiteit) - insecten - hoogveengebieden - moerassen - noord-brabant - culicidae - stinging - insects - moorlands - marshes - noord-brabant
    Het doel van het project ‘Stekende insecten rondom de Groote Peel’ is tweeledig: a) Het verrichten van een Quick-scan risico-analyse van het gebied Groote Peel en met name de mogelijke effecten van de voorgenomen maatregelen in het project LIFE+ op eventuele overlast veroorzaakt door steekmuggen en knutten. b) Het in 2016 rondom de Groote Peel uitvoeren van een nulmeting om inzicht te krijgen in en het vastleggen van het voorkomen van steekmuggen en knutten rondom de lokaal aanwezige bebouwing en nabij natte randzones.
    Stekende insecten Griendtsveen 2016
    Verdonschot, Piet F.M. ; Dekkers, Dorine D. - \ 2017
    Wageningen : Wageningen Environmental Research (Alterra), Zoetwatersystemen (Notitie / Zoetwaterecosystemen, Wageningen Environmental Research ) - ISBN 9789463431248 - 81
    insecten - steken (activiteit) - culicidae - moerassen - hoogveengebieden - noord-brabant - insects - stinging - culicidae - marshes - moorlands - noord-brabant
    Het doel van het project is het terugdringen van de steekmuggenoverlast in Griendtsveen door: 1) Het in het maatregelenpakket van LIFE+ in de Mariapeel opnemen van een aangepast peilbeheer om de ontwikkeling van langdurig tijdelijke wateren tegen te gaan en de isolatie van langdurig tijdelijke wateren op te heffen. Hiervoor dienen de langdurig tijdelijke wateren die functioneren als broedplaats voor moerassteekmuggen te worden gekarteerd en dient de gebiedshydrologie en –morfologie te worden vastgelegd om doelgerichte maatregelen te kunnen formuleren. 2) Het instellen van een monitoringsmeetnet om de overlast van stekende insecten in en rondom het dorp Griendtsveen te kunnen volgen in de tijd. 3) Eventueel de verbindingszone waarlangs moerassteekmuggen migreren van het natuurgebied naar het dorp zo in te richten dat deze dient als barrière voor stekende insecten.
    Push-pull strategie kan helpen bij bestrijden kieskeurige rouwmuggen
    Kruidhof, Marjolein ; Vijverberg, Ruben - \ 2016
    plant protection - pest control - animal behaviour - insect attractants - experimental design - culicidae - greenhouse horticulture
    A multidisciplinary approach to study virulence of the entomopathogenic fungus Beauveria bassiana towards malaria mosquitoes
    Valero Jimenez, C.A. - \ 2016
    Wageningen University. Promotor(en): Bas Zwaan; Willem Takken, co-promotor(en): Sander Koenraadt; Jan van Kan. - Wageningen : Wageningen University - ISBN 9789462578548 - 131
    beauveria bassiana - entomogenous fungi - virulence - vector control - mosquito-borne diseases - malaria - anopheles - culicidae - beauveria bassiana - entomopathogene schimmels - virulentie - vectorbestrijding - ziekten overgebracht door muskieten - malaria - anopheles - culicidae

    Although globally malaria mortality rates have fallen by 48% between 2000 and 2015, malaria is still killing an estimated 438,000 people each year. An effective way to alleviate the burden of malaria is to control its vector (malaria mosquitoes) using insecticides. This can be achieved either with insecticide-treated bed nets (ITNs) or through indoor residual spraying of insecticides (IRS). However, because of rapidly expanding insecticide resistance, there is a need to find alternatives to control the mosquitoes. Entomopathogenic fungi (EPF) could constitute an effective biological control tool, as is able to reduce malaria transmission under laboratory and field conditions. However, fundamental knowledge on the mechanisms and regulation of the infection process of the fungus, as well as insights into the defensive responses of the host insect to EPF, is limited. Therefore, the main goal of this thesis was to study virulence of the entomopathogenic fungus B. bassiana towards malaria mosquitoes using a multidisciplinary approach.

    Chapter 2 provides an overview of existing knowledge of genes influencing virulence in EPF, with a special focus on B. bassiana. The infection cycle and virulence mechanisms are discussed, and put in a framework of novel strategies and experimental methods that are needed to better understand virulence and improve the usage of EPF as a biocontrol agent.

    The study of natural variation in fungal virulence is a first step towards understanding the genetic mechanisms involved, because it reveals the extent of variation in the different components of virulence and their overall role. Chapter 3 describes the natural variation in virulence for 29 B. bassiana isolates that were tested on malaria mosquitoes. Furthermore, the phenotypic characteristics of the fungal isolates such as sporulation, spore size and growth were evaluated and their relationship with virulence analysed.

    Based on the ample natural variation observed in fungal virulence, in Chapter 4, a comparative genomics analysis was performed on five selected isolates of contrasting virulence. In order to understand mechanisms underlying contrasting virulence, a comparison on gene gain/loss, single nucleotide polymorphisms (SNPs), secreted proteins, and secondary metabolites was performed. Insight is provided to the magnitude of the complexity of a trait such as virulence and suggests candidate genes that can be further studied using a functional analysis approach.

    Chapter 5 focuses on an experimental evolution approach in which B. bassiana was solely using insects as a nutritional source for ten consecutive passages through malaria mosquitoes. Two isolates of B. bassiana that differed in virulence were compared to their respective ancestors, and they were assayed in virulence, fungal outgrowth, mycelial growth rate (MGR), and sporulation. Passage of the entomopathogenic fungi B. bassiana through the insect host resulted in an altered capacity to grow on different substrates while maintaining the ability to kill insects.

    Chapter 6 presents a discussion on the main findings of this thesis and describes future perspectives to study virulence of the entomopathogenic fungi Beauveria bassiana in the context of biological control of malaria mosquitoes.

    Combining malaria control with rural electrification : social and behavioural factors that influenced the design, use and sustainability of solar-powered mosquito trapping systems (SMoTS) for malaria elimination on Rusinga Island, western Kenya
    Oria, Prisca A. - \ 2016
    Wageningen University. Promotor(en): Cees Leeuwis; Willem Takken, co-promotor(en): J. Alaii. - Wageningen : Wageningen University - ISBN 9789462578579 - 176
    malaria - vector control - public health - culicidae - insect traps - social factors - behaviour - design - solar energy - kenya - malaria - vectorbestrijding - volksgezondheid - culicidae - insectenvallen - sociale factoren - gedrag - ontwerp - zonne-energie - kenya

    Chapter 1 presents the background information relevant to the subject matter and methods of this thesis. These include the application of social and behavioural sciences in malaria control, the SolarMal project and malaria in Kenya. It also presents the research objective, question and design that informed this thesis.

    Chapter 2 systematically documented and analysed how the mosquito trapping technology and related social contexts mutually shaped each other and how this mutual shaping impacted the design and re-design of the intervention. Our analysis focused on the design, re-design and piloting of the innovative approach to controlling malaria largely before its field implementation had started. During the pre-intervention year, various aspects of the intervention were re-designed ahead of the project roll-out. Changes to the technology design included removal of carbon dioxide from the blend, trap improvements and re- design of the electricity provision system. In order to gain and maintain the support of the community and organisations on the island, the project adapted its implementation strategies regarding who should represent the community in the project organisation team, who should receive solar-powered mosquito trapping systems (SMoTS), and in which order the systems should be rolled out. This process involved not only the project team and the producers of the different components of SMoTS, but also included feedback from the residents of Rusinga Island. This process of incorporating feedback from a broad range of stakeholders utilized data from the entomological, technical and socio-behavioural researches as well as data from more broad engagements with the social environment of the study population and setting. The analysis demonstrates how system innovation theory helps to provide insights into how a promising malaria control intervention evolves and matures through an interaction between technical and social phenomena. This part of the study demonstrated that SolarMal was not only a technical innovation, but similar to other malaria strategies, required new social organisational arrangements to go with it.

    In chapter 3, this thesis investigated immediate community response to the innovation and the implications for ongoing implementation and supportive community communication outreach. The explorations found that the main benefit of SMoTS to study participants was house lighting and suggested that the main reason that people adhered to recommended behaviours for SMoTS deployment was to ensure uninterrupted lighting at night, rather than reducing mosquito biting or malaria risk. Electrification led to a number of immediate benefits including reduced expenditure on kerosene and telephone charging and conveniences (such as lit early mornings and late nights, increased study hours, etc.). The changes brought about by electric lighting provided conveniences which improved the welfare of residents. Some respondents also reported hearing fewer mosquito sounds when interviewed a few weeks after a SMoTS was installed in their house. On the question of maintenance, we found that residents of Rusinga Island adequately maintained SMoTS. Households also reported maintenance needs to the project and project technicians carried out repair and maintenance needs.

    Chapter 4 documented the perceived impact of SMoTs on family dynamics, social and economic status, and the community as a whole. The findings suggest that even when the use of energy is restricted, electricity can enhance the value of life. Although data on malaria prevention was yet to be fully collected and analysed, there was evidence of enhanced socio-economic and emotional well-being of study participants which may enhance the desire to sustain the intervention. In the end, this may be a double-edged intervention that delivers health benefits and contributes to improved welfare. The utility, social significance and emotional benefits experienced with the lighting component of SMoTS may create the desire to sustain the intervention. However, the motivation to sustain the whole SMoTS will also depend on the results of the entomological and parasitological components of this intervention.

    Chapter 5 evaluated the knowledge, perceptions and practices related to malaria control before and after the roll-out of solar-powered mosquito trapping systems. As a malaria control strategy, SMoTS were installed in Rusinga to complement the existing use of long- lasting insecticidal nets (LLINS) and prompt malaria care seeking. The message about the complementariness of SMoTS as a malaria strategy was further stressed during social mobilisation to encourage continued use of LLINs and prompt malaria care seeking. The findings suggest that overall, the SolarMal project did not induce a negative effect of the innovation on the uptake of existing malaria strategies. The continuation of LLIN use and recommended malaria treatment seeking was likely contributed to by the social mobilisation component of the SolarMal intervention as well as a mass distribution of LLINs campaign, suggesting the need for a strong continuous demand generation exercise. The number of respondents who reported that mosquito densities had reduced was much higher at the end of the research phase confirming that the recorded entomological changes (that showed SMoTS had proved effective in controlling mosquitoes) had also been experienced by residents.

    Chapter 6 investigated whether the community preferred individual or cooperative solutions for organising the sustainability components of SMoTS, and whether and how known social dilemma factors could be recognised in the reasoning of actors. The findings of the explorations of sustainability of installed SMoTS beyond the research period did not portray a promising picture. While residents were unanimous that they would like to continue enjoying the benefits of SMoTS (especially house electrification), it appeared that residents preferred largely individual approaches. Yet the individual approaches suggested by residents for sustaining SMoTS may be realistic for sustaining only the lighting component. Sustaining the mosquito control component, which is what would impact malaria, requires more resources (than the lighting component) and may be better facilitated by more collective undertakings by residents. Residents expressed concerns about working collectively with others that seemed to suggest that the situation had features of a social dilemma.

    Chapter 7 synthesises the main findings. Subsequently, this results in the overall conclusions of the thesis that are discussed within the broader debates on research and policy. This thesis shows that SolarMal was not only a technical innovation, but required new social organisational arrangements to go with it. The intervention was a composite of which the technical component was one and focussing on it without the others may have negative implications for effectiveness. By implication, the scaling up of SMoTS will also require scaling-up the intervention process and social organisation that played a role in its effectiveness in the trial setting. This thesis also demonstrates the importance of flexibility and continuous learning in multiple spheres in a complex multidisciplinary innovative intervention to control malaria. The key addition to the knowledge base for similar public health programs is that intervention design is not a one-off occurrence and neither is implementation a linear process. Social science research was a core component in this process and the process required not only integrating social inquiry into the design, but also into planning, implementation, and monitoring. This contributed to ensuring that flexibility and adaptability to the local realities were built into the SolarMal intervention and contributed to the success of the intervention. Rather than project management, persons involved in rolling-out innovations should perhaps focus on adaptive and proactive management and on facilitating change. While managing emphasises control and certainty, an innovation process requires flexibility to allow continuous adaptations which characterise the process. In practice, this means keeping attuned to perceiving signals, analysing feedback loops and using those signals to mitigate what is not going well or amplify what is going well.

    Impact of odour-baited mosquito traps for malaria control : design and evaluation of a trial using solar-powered mosquito trapping systems in western Kenya
    Homan, T. - \ 2016
    Wageningen University. Promotor(en): Willem Takken; T.A. Smith. - Wageningen : Wageningen University - ISBN 9789462577435 - 224
    016-3935 - culicidae - mosquito-borne diseases - vector control - malaria - bait traps - odours - solar energy - randomized controlled trials - kenya - culicidae - ziekten overgebracht door muskieten - vectorbestrijding - malaria - vallen met lokaas - geurstoffen - zonne-energie - gestuurd experiment met verloting - kenya

    The parasites belonging to the genus Plasmodium are the cause of the second deadliest infectious disease in the world, malaria. Sub Saharan Africa harbours more than 90% of malaria attributable mortality and morbidity, and most deaths occur in children under 18 years old. Malaria is transmitted to humans by a bite of a Plasmodium infected arthropod vector from the genus Anopheles. Halfway the 20th century malaria was successfully eliminated from most developed countries, nonetheless in the third world effective control remains a laborious challenge. Intensive efforts undertaken to control and eventually eradicate malaria during the past decade have led to substantial reductions in morbidity and mortality. Conversely, scientists became increasingly aware that with the current preventative and curative tools against malaria successful eradication seems unlikely. Not only do current tools not suffice to attain that goal, their efficacy to control malaria as it is, maybe severely threatened. Proper treatment and diagnosis are becoming increasingly less effective because of the adaptive nature of the parasite. Parasites get resistance against drugs and carriers are more often found to have subclinical infections. Likewise prevention of malaria, by vector control, becomes less effective. Malaria vectors become resistant to insecticides and transmission patterns are shifting away from where preventive measures are functional: outside and during the day. It this gap where the SolarMal project experimented with a novel malaria vector control tool, complimentary to existing malaria control methods: odour-baited mosquito traps that mimic human beings to lure and kill mosquitoes to eventually reduce malaria. The ultimate aim of this thesis was to seek proof of principle of the effect of mass trapping of malaria vectors on malaria and mosquito densities by rolling out over 4000 odour-baited mosquito traps at household level on Rusinga Island, Kenya.

    Chapter 2 is a study protocol of the SolarMal project and provides a general understanding of how the objectives of the project are translated into a research design. The study comprises of a medical, an entomological and a sociological discipline. A multidisciplinary strategy is presented in which the intervention is explained. Experimental designs of all disciplines are introduced including time frames, participant eligibility, and randomisation. Furthermore, a general overview of the data collected and how it is evaluated and analysed using health and demographic surveillance and monitoring is provided.

    In chapter 3 a novel data collection and management platform is presented. The health and demographic surveillance as well as other disciplines in the project are an example of one of the first fully digital data collection systems in a low and middle income country. The development of digital questionnaires and the conducting of these by means of Open Data Kit software enabled the project to efficiently collect data. All residential structures were documented by GPS, and data of individuals attached. Converting the geo-located data to a geodatabase and displayed with Google Earth mobile made navigating from house to house an easy task. By daily uploading of data to the server at the project campus, scientists have access to a near real time database. Once uploaded to the server, data is transferred to the OpenHDS database in which the demography of the study population is updated accordingly. Data quality was further increased by a tool that looked for inconsistencies.

    In chapter 4 we explore what experimental design would fit the SolarMal project best. A stepped wedge cluster-randomized trial [SWCRT] design was chosen to make sure that the whole area would cross over from the control to the intervention arm over a period of two years. As elimination was the goal, universal coverage was required. Subsequently, strategies for randomization and crossover of clusters that could measure a possible intervention effect best were simulated with a generic model of disease transmission. Considering sufficient numbers and sizes of clusters a hierarchical SWCRT would best measure a possible effect of OBTs on Rusinga Island. Special care was given to quantifying spill over effects into the control arm. Finally, two new measures of intervention effectiveness are proposed.

    Chapter 5 reports on the outcomes of the health and demographic surveillance system on Rusinga Island. Running an HDSS is a thorough but complex method to monitor intervention effects in an area where health surveillance is minimal. As part of the overarching HDSS institution, INDEPTH, data collection methods and reporting are harmonious with many other HDSSs around the world. Demographic parameters are calculated and the HDSS practices are described.

    Chapter 6 uses the baseline cross sectional prevalence surveys to elucidate how the epidemiology of malaria on Rusinga Island. Firstly, the malaria distribution and hot spots are identified. Consequently, a standard epidemiological model and a geographically weighted regression are compared, and used to identify risk factors for malaria. The latter model, taking into account non-stationarity, performs better and is able to produce geographically varying risk factors. The strength of the relationship of risk factors for malaria are heterogeneous over the whole island, and for instance social economic status and occupation are strong predictors of malaria in some areas but less in other areas. Considering these risk factor distributions can aid in guiding the implementation of malaria intervention methods.

    Chapter 7 presents the main outcomes of the SolarMal project. The impact of OBTs on the prevalence of malaria is pronounced in the contemporaneous comparison between the intervened and the intervened arm. Comparison of baseline data with the intervened clusters does not yield significant effects. A strong decline in cases of clinical malaria was observed starting already in the baseline period, and therefore we cannot attribute this decline to the intervention. Effects on the most prominent malaria vector were large, whereas other vectors did not suffer under the intervention.

    Chapter 8 is a general discussion of the work provided. The most important implications of the thesis are discussed underscoring the societal and scientific relevance, and putting the research in a wider perspective. Unaddressed issues are raised and recommendations for further research are provided.

    Stekende insecten Griendtsveen : situatie 2015
    Verdonschot, P.F.M. ; Dekkers, T.B.M. ; Besse-Lototskaya, A.A. - \ 2015
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2680)
    culicidae - insecten - steken - steken (activiteit) - limburg - waterstand - culicidae - insects - stings - stinging - limburg - water level
    Naar aanleiding van het advies van de Tijdelijke Adviescommissie LIFE+ Mariapeel om een onderzoek naar de muggenoverlast te verrichten is door de gemeente Horst aan de Maas gezamenlijk met de provincie Limburg een onderzoeksopdracht aan Alterra – Wageningen UR verstrekt. Alterra is gevraagd om de muggenoverlast te monitoren en daarmee de nulsituatie vast te stellen, de mate van overlast aan te geven en te adviseren over de effecten van voorgenomen maatregelen op de overlast.
    Push-pull tactics to disrupt the host-seeking behaviour of malaria mosquitoes
    Menger, D.J. - \ 2015
    Wageningen University. Promotor(en): Willem Takken; Joop van Loon. - Wageningen : Wageningen University - ISBN 9789462576070 - 173
    culicidae - anopheles - vectoren, ziekten - malaria - gedrag bij zoeken van een gastheer - insectenlokstoffen - insectenafweermiddelen - insectenvallen - vectorbestrijding - culicidae - anopheles - disease vectors - malaria - host-seeking behaviour - insect attractants - insect repellents - insect traps - vector control

    Malaria remains a major health burden, especially in sub-Saharan Africa. The efficacy of the main vector control tools, insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is compromised by the development of physiological and behavioural resistance in the target mosquito species and by changes in the species composition of vector populations. These developments underline the need to develop novel vector control approaches which are complementary to insecticide-based methods. In this thesis, the potential of push-pull tactics as a tool to reduce malaria transmission is explored. It is described how the push-pull concept, originally designed for agricultural pest control, may be translated in a system that targets Anopheles mosquitoes. Several novel repellents are identified in the laboratory and a prototype push-pull system is tested in a semi-field setup. The system is improved and evaluated in a malaria endemic field setting and the push-pull approach is compared and combined with the existing practise of eave screening. Based on the experimental results it is concluded that (1) it is possible to reduce house entry of malaria and other mosquitoes using (spatial) repellents and/or attractant-baited traps; (2) the effect of repellents on house entry is larger and more consistent than the effect of attractant-baited traps; (3) the main function of the attractant-baited traps is to deplete mosquito populations through removal trapping; (4) the attractive and repellent components of the push-pull system complement each other and there is no or very little interaction between them; (5) a push-pull system based on repellent and attractive volatiles can be expected to reduce malaria transmission through a strong decrease of the entomological inoculation rate; (6) eave screening is a highly efficient method to reduce house entry of malaria and other mosquitoes and increases outdoor trap catches, while there is little added value in impregnating screening material with a repellent. In the last chapter, the issue of selection for insensitivity to the used compounds is discussed, as well as methods how to manage it. Furthermore, it is described how the principles of behavioural disruption on which push-pull tactics are based make the technique potentially suitable to target a wider selection of arthropod vectors of disease than malaria mosquitoes alone. It is concluded that future vector control strategies will probably consist of the integration of many different approaches, of which push-pull tactics may be one. By integrating different approaches, it will be possible mitigate the development of resistance while targeting vectors in different life stages, uncompromised by changing behavioural patterns and changes in the composition of vector populations. This would require an integrated view on vector control, knowledge on the ecology of vectors and the political will to invest in programmes that focus on long term sustainable control.

    Mosquito attraction: crucial role of carbon dioxide in formulation of a five-component blend of human-derived volatiles
    Loon, J.J.A. van; Smallegange, R.C. ; Bukovinszkine-Kiss, G. ; Jacobs, F. ; Rijk, M. de; Mukabana, W.R. ; Verhulst, N.O. ; Menger, D.J. ; Takken, W. - \ 2015
    Journal of Chemical Ecology 41 (2015)6. - ISSN 0098-0331 - p. 567 - 573.
    gambiae-sensu-stricto - ionotropic glutamate receptors - vector anopheles-gambiae - human skin microbiota - malaria mosquito - semifield conditions - aedes-aegypti - lactic-acid - behavior - culicidae
    Behavioral responses of the malaria mosquito Anopheles coluzzii (An. gambiae sensu stricto molecular 'M form') to an expanded blend of human-derived volatiles were assessed in a dual-port olfactometer. A previously documented attractive three-component blend consisting of NH3, (S)-lactic acid, and tetradecanoic acid served as the basis for expansion. Adding 4.5 % CO2 to the basic blend significantly enhanced its attractiveness. Expansion of the blend with four human-derived C4-volatiles was then assessed, both with and without CO2. Only when CO2 was offered simultaneously, did addition of a specific concentration of 3-methyl-1-butanol or 3-methyl-butanoic acid significantly enhance attraction. The functional group at the terminal C of the 3-methyl-substituted C4 compounds influenced behavioral effectiveness. In the absence of CO2, addition of three concentrations of butan-1-amine caused inhibition when added to the basic blend. In contrast, when CO2 was added, butan-1-amine added to the basic blend strongly enhanced attraction at all five concentrations tested, the lowest being 100,000 times diluted. The reversal of inhibition to attraction by adding CO2 is unique in the class Insecta. We subsequently augmented the three-component basic blend by adding both butan-1-amine and 3-methyl-1-butanol and optimizing their concentrations in the presence of CO2 in order to significantly enhance the attractiveness to An. coluzzii compared to the three- and four-component blends. This novel blend holds potential to enhance malaria vector control based on behavioral disruption.
    Understanding the long-lasting attraction of malaria mosquitoes to odor baits
    Mweresa, C.K. ; Otieno, B. ; Omusula, P. ; Weldegergis, B.T. ; Verhulst, N.O. ; Dicke, M. ; Loon, J.J.A. van; Takken, W. ; Mukabana, W.R. - \ 2015
    PLoS ONE 10 (2015)3. - ISSN 1932-6203 - 16 p.
    gambiae-sensu-stricto - human skin emanations - anopheles-gambiae - human pathogen - aedes-aegypti - human sweat - identification - culicidae - volatiles - behavior
    The use of odor baits for surveillance and control of malaria mosquitoes requires robust dispensing tools. In this study, the residual activity of a synthetic mosquito attractant blend dispensed from nylon or low density polyethylene (LDPE) sachets was evaluated at weekly intervals for one year without re-impregnation. The potential role of bacteria in modulating the attraction of mosquitoes to odor-treated nylon that had been used repeatedly over the one year study period, without re-impregnation, was also investigated. Significantly higher proportions of female Anopheles gambiae sensu stricto mosquitoes were consistently attracted to treated nylon strips than the other treatments, up to one year post-treatment. Additional volatile organic compounds and various bacterial populations were found on the treated nylon strips after one year of repeated use. The most abundant bacteria were Bacillus thuringiensis and Acinetobacter baumannii. Autoclaving of treated nylon strips prior to exposure had no effect on trap collections of laboratory-reared female An. Gambiae (P = 0.17) or wild female An. Gambiae sensu lato (P = 0.26) and Mansonia spp. (P = 0.17) mosquitoes. Trap catches of wild female An. Funestus (P <0.001) and other anophelines (P <0.007) were higher when treated strips had been autoclaved prior to deployment as opposed to when the treated nylon strips were not autoclaved. By contrast, wild female Culex mosquitoes were more strongly attracted to non-autoclaved compared to autoclaved treated nylon strips (P <0.042). This study demonstrates the feasibility of using odor baits for sampling and surveillance of malaria as well as other mosquito vectors over prolonged periods of time. Preliminary evidence points towards the potential role of bacteria in sustaining prolonged use of nylon material for dispensing synthetic attractant odorants for host-seeking malaria and other mosquito vectors but further investigations are required.
    Modeling larval malaria vector habitat locations using landscape features and cumulative precipitation measures
    Mc Cann, R.S. ; Messina, J.P. ; MacFarlane, D.W. ; Bayoh, M.N. ; Vulule, J.M. ; Gimnig, J.E. ; Walker, E.D. - \ 2014
    International Journal of Health Geographics 13 (2014). - ISSN 1476-072X - 12 p.
    gambiae complex diptera - western kenya highlands - high-spatial-resolution - anopheles-gambiae - land-cover - child-mortality - breeding habitats - culicidae - africa - risk
    BACKGROUND: Predictive models of malaria vector larval habitat locations may provide a basis for understanding the spatial determinants of malaria transmission. METHODS: We used four landscape variables (topographic wetness index [TWI], soil type, land use-land cover, and distance to stream) and accumulated precipitation to model larval habitat locations in a region of western Kenya through two methods: logistic regression and random forest. Additionally, we used two separate data sets to account for variation in habitat locations across space and over time. RESULTS: Larval habitats were more likely to be present in locations with a lower slope to contributing area ratio (i.e. TWI), closer to streams, with agricultural land use relative to nonagricultural land use, and in friable clay/sandy clay loam soil and firm, silty clay/clay soil relative to friable clay soil. The probability of larval habitat presence increased with increasing accumulated precipitation. The random forest models were more accurate than the logistic regression models, especially when accumulated precipitation was included to account for seasonal differences in precipitation. The most accurate models for the two data sets had area under the curve (AUC) values of 0.864 and 0.871, respectively. TWI, distance to the nearest stream, and precipitation had the greatest mean decrease in Gini impurity criteria in these models. CONCLUSIONS: This study demonstrates the usefulness of random forest models for larval malaria vector habitat modeling. TWI and distance to the nearest stream were the two most important landscape variables in these models. Including accumulated precipitation in our models improved the accuracy of larval habitat location predictions by accounting for seasonal variation in the precipitation. Finally, the sampling strategy employed here for model parameterization could serve as a framework for creating predictive larval habitat models to assist in larval control efforts.
    Solarmal - Malaria control without poison
    Takken, Willem - \ 2014
    malaria - disease prevention - culicidae - innovations - system innovation - living conditions - public health - kenya
    Hybridization studies to modify the host preference of Anopheles gambiae
    Pates, H.V. ; Curtis, C.F. ; Takken, W. - \ 2014
    Medical and Veterinary Entomology 28 (2014)S1. - ISSN 0269-283X - p. 68 - 74.
    candidate odorant receptors - malaria vector mosquito - feeding preferences - quadriannulatus - behavior - arabiensis - culicidae - diptera - transmission - responses
    A strategy to decrease the vector competence of Anopheles gambiae sensu stricto (Diptera: Culicidae), the most efficient malaria vector in Africa, may consist of exploiting the genes involved in zoophily. Crossing and backcrossing experiments were performed between An.¿gambiae s.s. and the zoophilic sibling species Anopheles quadriannulatus. Mosquito strains were tested in a dual-choice olfactometer to investigate their responses to cow odour. Totals of 12% of An.¿gambiae s.s. and 59% of An.¿quadriannulatus selected the port with the cow odour. Crosses and backcrosses did not show a significant preference for the cow-baited port. The results indicated that anthropophilic behaviour in An.¿gambiae s.s. is a dominant or partially dominant trait, which, in conjunction with the unstable zoophilic behaviour observed in An.¿quadriannulatus, poses a serious obstacle to plans to decrease vector competence by modifying the anthropophilic trait.
    A global assembly of adult female mosquito mark-release-recapture data to inform the control of mosquito-borne pathogens
    Guerra, C.A. ; Reiner Jr, R.C. ; Perkins, T.A. ; Lindsay, S.W. ; Midega, J.T. ; Brady, O.J. ; Barker, C.M. ; Reisen, W.K. ; Harrington, L.C. ; Takken, W. ; Kitron, U. ; Lloyd, A.L. ; Hay, S.I. ; Scott, T.W. ; Smith, D.L. - \ 2014
    Parasites & Vectors 7 (2014). - ISSN 1756-3305 - 15 p.
    dominant anopheles vectors - plasmodium-falciparum transmission - distribution maps - bionomic precis - human malaria - sensitivity-analysis - population-dynamics - mathematical-model - aedes-aegypti - culicidae
    Background Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating such parameters including dispersal, population size and density, survival, blood feeding frequency and blood meal host preferences. Methods We assembled a comprehensive database describing adult female MMRR experiments. Bibliographic searches were used to build a digital library of MMRR studies and selected data describing the reported outcomes were extracted. Results The resulting database contained 774 unique adult female MMRR experiments involving 58 vector mosquito species from the three main genera of importance to human health: Aedes, Anopheles and Culex. Crude examination of these data revealed patterns associated with geography as well as mosquito genus, consistent with bionomics varying by species-specific life history and ecological context. Recapture success varied considerably and was significantly different amongst genera, with 8, 4 and 1% of adult females recaptured for Aedes, Anopheles and Culex species, respectively. A large proportion of experiments (59%) investigated dispersal and survival and many allowed disaggregation of the release and recapture data. Geographic coverage was limited to just 143 localities around the world. Conclusions This MMRR database is a substantial contribution to the compilation of global data that can be used to better inform basic research and public health interventions, to identify and fill knowledge gaps and to enrich theory and evidence-based ecological and epidemiological studies of mosquito vectors, pathogen transmission and disease prevention. The database revealed limited geographic coverage and a relative scarcity of information for vector species of substantial public health relevance. It represents, however, a wealth of entomological information not previously compiled and of particular interest for mosquito-borne pathogen transmission models.
    A push-pull system to reduce house entry of malaria mosquitoes
    Menger, D.J. ; Otieno, B. ; Rijk, M. de; Mukabana, W.R. ; Loon, J.J.A. van; Takken, W. - \ 2014
    Malaria Journal 13 (2014). - ISSN 1475-2875 - 8 p.
    vector anopheles-gambiae - host-seeking behavior - mm-x traps - spatial repellency - field-evaluation - western kenya - lactic-acid - culicidae - diptera - strategies
    Background. Mosquitoes are the dominant vectors of pathogens that cause infectious diseases such as malaria, dengue, yellow fever and filariasis. Current vector control strategies often rely on the use of pyrethroids against which mosquitoes are increasingly developing resistance. Here, a push-pull system is presented, that operates by the simultaneous use of repellent and attractive volatile odorants. Method/Results. Experiments were carried out in a semi-field set-up: a traditional house which was constructed inside a screenhouse. The release of different repellent compounds, para-menthane-3,8-diol (PMD), catnip oil e.o. and delta-undecalactone, from the four corners of the house resulted in significant reductions of 45% to 81.5% in house entry of host-seeking malaria mosquitoes. The highest reductions in house entry (up to 95.5%), were achieved by simultaneously repelling mosquitoes from the house (push) and removing them from the experimental set-up using attractant-baited traps (pull). Conclusions. The outcome of this study suggests that a push-pull system based on attractive and repellent volatiles may successfully be employed to target mosquito vectors of human disease. Reductions in house entry of malaria vectors, of the magnitude that was achieved in these experiments, would likely affect malaria transmission. The repellents used are non-toxic and can be used safely in a human environment. Delta-undecalactone is a novel repellent that showed higher effectiveness than the established repellent PMD. These results encourage further development of the system for practical implementation in the field.
    Assessing the efficacy of candidate mosquito repellents against the background of an attractive source that mimics a human host
    Menger, D.J. ; Loon, J.J.A. van; Takken, W. - \ 2014
    Medical and Veterinary Entomology 28 (2014)4. - ISSN 0269-283X - p. 407 - 413.
    anopheles-gambiae - malaria mosquito - behavioral-response - carbon-dioxide - human skin - culicidae - diptera - aedes - identification - odor
    Mosquito repellents are used around the globe to protect against nuisance biting and disease-transmitting mosquitoes. Recently, there has been renewed interest in the development of repellents as tools to control the transmission of mosquito-borne diseases. We present a new bioassay for the accurate assessment of candidate repellent compounds, using a synthetic odour that mimics the odour blend released by human skin. Using DEET (N,N-diethyl-meta-toluamide) and PMD (p-menthane-3,8-diol) as reference compounds, nine candidate repellents were tested, of which five showed significant repellency to the malaria mosquito Anopheles gambiae sensu stricto (Diptera: Culicidae). These included: 2-nonanone; 6-methyl-5-hepten-2-one; linalool; d-decalactone, and d-undecalactone. The lactones were also tested on the yellow fever mosquito Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae), against which they showed similar degrees of repellency. We conclude that the lactones are highly promising repellents, particularly because these compounds are pleasant-smelling, natural products that are also present in human food sources.
    Koenraadt, C.J.M. ; Vogels, C.B.F. ; Peppel, L. van de; Vliet, A.J.H. van; Bron, W.A. - \ 2014
    Wageningen UR
    culicidae - insectenbeten - monitoring - inventarisaties - culicidae - insect bites - monitoring - inventories
    Onderzoekers van Wageningen University analyseerden de door hen verzamelde, platgeslagen muggen (januari en februari 2014). De overlast werd voornamelijk veroorzaakt door de molestusmug. Die verwant is aan de huissteekmug. De meeste muggen zijn afkomstig uit de provincie Zud-Holland.
    Odour-based strategies for surveillance and behavioural disruption of host-seeking malaria and other mosquitoes
    Mweresa, C.K. - \ 2014
    Wageningen University. Promotor(en): Willem Takken; Marcel Dicke; W.R. Mukabana; Joop van Loon. - Wageningen : Wageningen University - ISBN 9789461739247 - 277
    anopheles gambiae - anopheles funestus - anopheles - culicidae - semiochemicals - insectenlokstoffen - lokstoffen - synthetische materialen - geurstoffen - malaria - gedrag bij zoeken van een gastheer - anopheles gambiae - anopheles funestus - anopheles - culicidae - semiochemicals - insect attractants - attractants - synthetic materials - odours - malaria - host-seeking behaviour
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