Search

Adults of many mosquito species feed on plants to obtain metabolic energy and to enhance reproduction. Mosquitoes primarily rely on olfaction to locate plants and are known to respond to a range of plant volatiles. We studied the olfactory response of the yellow fever mosquito Aedes aegypti to methyl jasmonate (MeJA) and cis-jasmone (CiJA), volatile compounds originating from the octadecanoid signaling pathway that plays a key role in plant defense against herbivores. Specifically, we investigated how Ae. aegypti of different ages responded to elevated levels of CiJA in two attractive odor contexts, either derived from Lima bean plants or from human skin. Aedes aegypti females landed significantly less often on a surface with CiJA and MeJA compared to the solvent control, CiJA exerting a stronger reduction in landing than MeJA. Odor context (plant or human) had no significant main effect on the olfactory responses of Ae. aegypti females to CiJA. Mosquito age significantly affected the olfactory response, older females (7–9 d) responding more strongly to elevated levels of CiJA than young females (1–3 d) in either odor context. Our results show that avoidance of CiJA by Ae. aegypti is independent of odor background, suggesting that jasmonates are inherently aversive cues to these mosquitoes. We propose that avoidance of plants with elevated levels of jasmonates is adaptive to mosquitoes to reduce the risk of encountering predators that is higher on these plants, i.e. by avoiding ‘enemy-dense-space’.

Inademing van de geurstoffen isoeugenol en cinnamal leidt bij muizen tot een immuunreactie in de ademhalingswegen. Dat blijkt uit experimenten uitgevoerd door het RIVM. Deze resultaten geven aan dat inademing van sommige geurstoffen zou kunnen leiden tot ongewenste effecten op het immuunsysteem. Geurstoffen komen voor in verschillende consumentenproducten, zoals cosmetica en geurproducten. Van verscheidene geurstoffen is bekend dat ze via de huid allergie kunnen veroorzaken, maar het is onbekend of ze ook allergische klachten of andere ongewenste immuunreacties kunnen veroorzaken via inademing. Tot nu toe is aangenomen dat inademing van geurstoffen niet schadelijk is voor de mens, omdat er geen blootstelling was via de ademhaling. De toepassing in geurproducten binnenshuis heeft hierin verandering gebracht. Het RIVM onderzocht in experimenten de effecten van inademing van isoeugenol en cinnamal, geurstoffen die huidallergie kunnen veroorzaken. Muizen werden via inademing blootgesteld aan de geurstoffen. De effecten op het immuunsysteem werden gemeten met de respiratoire lymfkliertest, die celdeling als reactie meet in de lymfeklieren van de ademhalingswegen. Inademing van zowel isoeugenol als cinnamal resulteerde in een stimulatie van het immuunsysteem van de ademhalingswegen. De effecten van isoeugenol waren sterker dan die van cinnamal. Dit is een verschil met blootstelling via de huid, waarbij beide geurstoffen eenzelfde potentie hebben om huidallergie te veroorzaken. Dit kan betekenen dat de effecten van geurstoffen op het immuunsysteem afhangen van de toedieningsroute. Om het gevaar van inademing van deze stoffen te kunnen voorspellen, zal de relevante blootstellingsroute moeten worden gebruikt. Voor cosmetica is dat via de huid, voor geurproducten via inademing. Om meer inzicht te krijgen in de risico's van geurstoffen in geurproducten, raadt het RIVM aan om meer geurstoffen te testen met de respiratoire lymfkliertest.

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.

The obesogenic environment we live in is characterized by an abundance of available foods and food cues that tempt us to eat. Throughout our lives we learn to associate these food cues (odours, pictures) with physiological consequences of food consumption. The sense of smell is suggested to be very important for determining food quality, guiding us away from spoilt food and towards rewarding foods. Increased sensitivity to environmental cues of rewarding food, decreased sensitivity to physiological cues of hunger and a decreased ability to control impulses are thought to contribute to overeating and obesity. With the research in this thesis we aimed to elucidate the role of odours in (over)eating, to better understand how sensory food cues and hunger feelings are involved in determining our eating pattern. We assessed the appetizing effects of exposure to odours signalling food with a certain taste (sweet/savoury) and energy density (high/low). Our findings show that smelling a food odour increases appetite for foods that are similar to the odour, both in terms of taste and energy density. These appetizing effects were present when participants were hungry but also when they had just eaten, indicating a possible role in overeating. Further, consumption of a high-energy food with a certain taste (sweet/savoury) led to a decrease in liking and wanting of foods with a similar taste and energy density. Next to this, we observed more pronounced changes in early neural processing of pictures of high-energy/sweet food after consumption of a high-energy/sweet meal. Food preferences and -intake after ambient exposure to odours signalling high-energy food, low-energy food and non-food were not different. Odours did not affect these measures of eating behaviour differently in a hungry or satiated state and in normal-weight or overweight participants. In a group of patients who underwent Roux-en-Y Gastric Bypass weight-loss surgery, we found a shift in food preferences away from high-fat/high-sugar and towards low-fat/low-sugar foods and altered activation in the frontoparietal neural network during (food) cue processing. After compared to before surgery we also found altered prefrontal neural responses when patients inhibited their responses to pictures of high-energy food. These results suggest that RYGB leads to changes in cognitive control of attention and increased neural inhibitory control over behavioural responses. In conclusion, odours have a specific appetizing function in the anticipatory phase of eating. They are important in determining the taste quality and energy-density and may be involved in the selection of foods for macronutrient regulation. Orthonasal odours should be used to guide food selection towards a healthier eating pattern.

Background and aim Traditional liking ratings are typically seen as an important determinant in eating behavior. However, in order to better understand eating behavior, we need to first better understand (the dynamic and implicit features underlying) liking appraisal. The aim of this thesis was to investigate the effects of food stimuli varying in sensory modality (smell and taste), pleasantness and intensity, on emotional and physiological responses leading up to liking appraisal. Methods Four studies, using healthy participants, were conducted as part of this thesis. In the first study, responses to pleasant versus unpleasant food odors varying in intensity were measured discretely using pleasantness ratings, intensity ratings and non-verbally reported emotions (PrEmo), as well as continuously using facial expressions and autonomic nervous system (ANS) responses. To further explore how explicit and implicit factors contribute to pleasantness appraisal, the same measures were assessed in response to food odors with a wider range of valence. Next, we focused on facial expressions and ANS responses elicited by single sips of breakfast drinks that were equally liked. In the last study, we investigated changes in pleasantness after consuming semi-liquid meals to (sensory-specific) satiety, combined with measures of facial expressions and ANS responses. Results Both non-verbal reported emotions and emotional facial expressions were demonstrated to be able to discriminate between food odors differing in pleasantness and between food odors differing in intensity. In addition to discrete emotional responses, odor valence associated best with facial expressions after 1 second of odor exposure. Furthermore, facial expressions and ANS responses measured continuously were found odor-specific in different rates over time. Results of food odors with a wider range of valence showed that non-verbally reported emotions, facial expressions and ANS responses correlated with each other best in different time windows after odor presentation: facial expressions and ANS responses correlated best with the explicit emotions of the arousal dimension in the 2nd second of odor presentation, whereas later ANS responses correlated best with the explicit emotions of the valence dimension in the 4th second. For food stimuli varying in flavor (breakfast drinks), facial expressions and ANS responses showed strongest associations with liking after 1 second of tasting, as well as with intensity after 2 seconds of tasting. Lastly, we were able to demonstrate that ANS responses, as well as facial expressions of anger and disgust were associated with satiety. Further effects of sensory-specific satiety were also reflected by skin conductance, skin temperature, as well as facial expressions of sadness and anger. Conclusions Both non-verbal reported emotions and emotional facial expressions were demonstrated to be able to discriminate between food odors differing in pleasantness and/or intensity. Explicit and implicit emotional responses, as well as physiological patterns are related to liking appraisals involved in smelling foods. Implicit measures such as facial expressions and ANS responses can provide more multidimensional information for both food odors and tastes than explicit measures and prove to be highly dynamic over time with specific time courses. Early implicit facial and ANS responses primarily reflect emotion arousal, whereas later ANS responses reflect emotion valence, suggesting dynamic unfolding of different appraisals of food stimuli. Furthermore, ANS responses and facial expressions can reflect pleasantness, satiety, and a combination of both: sensory-specific satiety. This suggests that implicit processes play an important role in dynamic liking appraisals with respect to eating behavior.

Background and aim Traditional liking ratings are typically seen as an important determinant in eating behavior. However, in order to better understand eating behavior, we need to first better understand (the dynamic and implicit features underlying) liking appraisal. The aim of this thesis was to investigate the effects of food stimuli varying in sensory modality (smell and taste), pleasantness and intensity, on emotional and physiological responses leading up to liking appraisal. Methods Four studies, using healthy participants, were conducted as part of this thesis. In the first study, responses to pleasant versus unpleasant food odors varying in intensity were measured discretely using pleasantness ratings, intensity ratings and non-verbally reported emotions (PrEmo), as well as continuously using facial expressions and autonomic nervous system (ANS) responses. To further explore how explicit and implicit factors contribute to pleasantness appraisal, the same measures were assessed in response to food odors with a wider range of valence. Next, we focused on facial expressions and ANS responses elicited by single sips of breakfast drinks that were equally liked. In the last study, we investigated changes in pleasantness after consuming semi-liquid meals to (sensory-specific) satiety, combined with measures of facial expressions and ANS responses. Results Both non-verbal reported emotions and emotional facial expressions were demonstrated to be able to discriminate between food odors differing in pleasantness and between food odors differing in intensity. In addition to discrete emotional responses, odor valence associated best with facial expressions after 1 second of odor exposure. Furthermore, facial expressions and ANS responses measured continuously were found odor-specific in different rates over time. Results of food odors with a wider range of valence showed that non-verbally reported emotions, facial expressions and ANS responses correlated with each other best in different time windows after odor presentation: facial expressions and ANS responses correlated best with the explicit emotions of the arousal dimension in the 2nd second of odor presentation, whereas later ANS responses correlated best with the explicit emotions of the valence dimension in the 4th second. For food stimuli varying in flavor (breakfast drinks), facial expressions and ANS responses showed strongest associations with liking after 1 second of tasting, as well as with intensity after 2 seconds of tasting. Lastly, we were able to demonstrate that ANS responses, as well as facial expressions of anger and disgust were associated with satiety. Further effects of sensory-specific satiety were also reflected by skin conductance, skin temperature, as well as facial expressions of sadness and anger. Conclusions Both non-verbal reported emotions and emotional facial expressions were demonstrated to be able to discriminate between food odors differing in pleasantness and/or intensity. Explicit and implicit emotional responses, as well as physiological patterns are related to liking appraisals involved in smelling foods. Implicit measures such as facial expressions and ANS responses can provide more multidimensional information for both food odors and tastes than explicit measures and prove to be highly dynamic over time with specific time courses. Early implicit facial and ANS responses primarily reflect emotion arousal, whereas later ANS responses reflect emotion valence, suggesting dynamic unfolding of different appraisals of food stimuli. Furthermore, ANS responses and facial expressions can reflect pleasantness, satiety, and a combination of both: sensory-specific satiety. This suggests that implicit processes play an important role in dynamic liking appraisals with respect to eating behavior.

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.

Onder laboratoriumomstandigheden blijkt het goed mogelijk om een Botrytis-infectie in tomatenplanten te detecteren met behulp van vluchtige stoffen. Onderzoekers van Wageningen Universiteit en Plant Research International bekijken nu of het mogelijk is om deze stoffen te detecteren in een kas zodat ziekten en plagen mogelijk in een zeer vroeg stadium opgespoord kunnen worden

In twee identieke afdelingen met vleesvarkens is het effect gemeten van het aanbrengen van probiotica (PIP) via het vernevelen er van in de afdeling. Uit de gemeten waarden blijkt er geen significant effect te zijn van het toepassen van probiotica op de emissies van ammoniak (NH3), geur en fijnstof (PM10) en de concentratie van ammoniak.

This study explored new possibilities to control whiteflies in greenhouse ornamental crops with omnivorous predatory bugs and volatiles. Besides the well-known Macrolophus pygmaeus, we tested 4 new species of predatory bugs: Dicyphus errans, Dicyphus eckerleini, Dicyphus maroccanus and Dicyphus tamaninii. We assessed both their potential to control whiteflies and their possible plant damaging effects through plant feeding. The best control of whiteflies was achieved by the species M. pygmaeus, D. tamaninii and D. maroccanus. Significant flower damage was only observed for the predator M. pygmaeus. The degree of flower damage depended strongly on the gerbera cultivar, but damage was observed for both large-flowered and small-flowered types. All 5 species of predatory bugs were able to establish in a winter crop of 2 gerbera cultivars and the exotic plant Lantana camara. The most promising candidate predatory bug for biological control in gerbera is D. maroccanus. This species established well on the 2 tested gerbera cultivars, gave in all cases an excellent control of pests and no significant plant damage was observed. The predatory bugs gave, besides whiteflies, a good control of Echinothrips and in some cases a suppression of aphids and western flower thrips. The volatile limonene showed no significant effect on the oviposition of tobacco and greenhouse whiteflies. Neither did they repel adults of these whiteflies. The mixture of (E)-2-hexenal and 3-hexen-1-ol did not induce a significant attraction response of the adult whiteflies. In dit onderzoek is gekeken naar nieuwe mogelijkheden voor bestrijding van wittevlieg in de sierteelt onder glas met omnivore roofwantsen en geuren. Naast de bekende Macrolophus pygmaeus zijn voor deze studie 4 nieuwe soorten roofwantsen verzameld, namelijk Dicyphus errans, Dicyphus eckerleini, Dicyphus maroccanus en Dicyphus tamaninii. Deze zijn beoordeeld op hun potentie om wittevlieg te bestrijden en tegelijkertijd op hun mogelijke negatieve effecten op de productie van gerberabloemen. Wittevlieg werd het meest effectief bestreden door M. pygmaeus, D. tamaninii en D. maroccanus. Significante bloemschade in gerbera is alleen aangetoond voor de roofwants M. pygmaeus. De schadegevoeligheid blijkt sterk te verschillen tussen cultivars, maar trad op bij zowel groot- als kleinbloemigen. Alle 5 de soorten roofwantsen vestigden zich goed gedurende een winterperiode op gerbera en de kuipplant Lantana camara. Van alle roofwantsen lijkt D. maroccanus de meest interessante kandidaat te zijn voor biologische bestrijding in gerbera. Er was een goede vestiging op de 2 geteste cultivars, in alle gevallen een goede plaagbestrijding en er is géén significante schade geconstateerd. Naast wittevlieg, gaven de roofwantsen een goede bestrijding van Echinothrips en er was een nevenwerking op bladluis en californische trips. De geurstof limoneen had géén significant effect op de eileg of afstoting van kas- en tabakswittevlieg. Ook werden de wittevliegen niet aangetrokken door een mengsel van (E)-2-hexanal en 3-hexen-1-ol.

Plaagwantsen zoals behaarde wants en brandnetelwants vormen in teelten als aubergine, komkommer en chrysant een serieus probleem. Ze geven al in kleine aantallen flinke schade: bloemabortie in aubergine, stengel- en vruchtschade in komkommer en splitkoppen in chrysant. Zodra telers wantsen of wantsenschade signaleren zien ze zich al snel genoodzaakt in te grijpen met middelen die schadelijk zijn voor aanwezige biologische bestrijders tegen andere plagen; het begin van het einde van hun biologie.

This study explored new possibilities to control whiteflies in greenhouse ornamental crops with omnivorous predatory bugs and volatiles. Besides the well-known Macrolophus pygmaeus, we tested 4 new species of predatory bugs: Dicyphus errans, Dicyphus eckerleini, Dicyphus maroccanus and Dicyphus tamaninii. We assessed both their potential to control whiteflies and their possible plant damaging effects through plant feeding. The best control of whiteflies was achieved by the species M. pygmaeus, D. tamaninii and D. maroccanus. Significant flower damage was only observed for the predator M. pygmaeus. The degree of flower damage depended strongly on the gerbera cultivar, but damage was observed for both large-flowered and small-flowered types. All 5 species of predatory bugs were able to establish in a winter crop of 2 gerbera cultivars and the exotic plant Lantana camara. The most promising candidate predatory bug for biological control in gerbera is D. maroccanus. This species established well on the 2 tested gerbera cultivars, gave in all cases an excellent control of pests and no significant plant damage was observed. The predatory bugs gave, besides whiteflies, a good control of Echinothrips and in some cases a suppression of aphids and western flower thrips. The volatile limonene showed no significant effect on the oviposition of tobacco and greenhouse whiteflies. Neither did they repel adults of these whiteflies. The mixture of (E)-2-hexenal and 3-hexen-1-ol did not induce a significant attraction response of the adult whiteflies.

In twee identieke afdelingen met vleesvarkens is het effect gemeten van het aanbrengen van probiotica (PIP) via het vernevelen er van in de afdeling. Uit de gemeten waarden blijkt er geen significant effect te zijn van het toepassen van probiotica op de emissies van ammoniak (NH3), geur en fijnstof (PM10) en de concentratie van ammoniak.

Plantengeuren die de planten afgeven na vraat door een herbivoor insect worden door hun natuurlijke vijanden gebruikt om hun prooi te vinden. Hierover is al meer dan 25 jaar onderzoek gedaan. Recent onderzoek in het tritrofe systeem van limaboonplanten (Phaseolus lunatus), spintmijten (Tetranychus urticae) en roofmijten (Phytoseiulus persimilis) heeft uitgewezen dat roofmijten met behulp van herbivoor-geïnduceerde plantengeuren hun prooi ook kunnen vinden in een omgeving met diverse soorten planten en herbivoren.

Plantengeuren spelen een belangrijke rol in ons leven. Desondanks is de eigenschap geur jarenlang miskend en verwaarloosd bij de selectie van nieuwe cultivars. PPO Bomen deed onderzoek naar geur bij een groot aantal boomkwekerij-gewassen. In dit artikel een overzicht van geurige gewassen voor de tuin

Air treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and waterAir treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and water. The prototype "ENOBE" electronic nose is based on an array of eight thickness shear mode resonators (TSMR), also known in the literature as quartz microbalance sensors. The chemical sensitivity is given by molecular films of metalloporphyrins and similar compounds. Chemical interaction of compounds in the air with the vibrating sensors induces a frequency change of the vibration that can be measured as a signal. The air from the mouse cage had a strong odour (3490 OUE/m(3)). The biological membrane filter performed well, achieving over 80% odour and ammonia reduction. The electronic nose signal could be correlated with the inlet and outlet air-quality of the biological filter, making it a promising method for monitoring air quality in closed environments.

Malaria mosquitoes use host odours to find their blood sources, but little is known about the semiochemicals that mediate this behaviour. A combined study is undertaken to identify the volatile human-specific compounds that are used in the host-seeking behaviour of the females of Anopheles gambiae

Er is weinig bekend over de risico's als gevolg van de blootstelling van consumenten aan geurstoffen uit consumentenproducten. Toevoeging van deze stoffen vindt plaats aan tal van consumentenproducten, varierend van wasmiddelen tot speelgoed. Passieve huiskamerparfums en spuitbusparfums zijn twee groepen producten die populair zijn in gebruik en die voor langdurige dan wel hoge blootstelling van de consument aan chemische stoffen kunnen zorgen. Voor het schatten van de mate van deze blootstelling is het softwareprogramma ConsExpo beschikbaar. Bijzondere aandacht gaat in deze studie uit naar het risico van het inademen van geurstoffen waarvan bekend is dat ze bij contact met de huid een allergische reactie kunnen veroorzaken. Door een gebrek aan een geaccepteerde methode echter, is het op dit moment niet mogelijk om te bepalen of dergelijke allergische reacties ook kunnen optreden bij inademing van deze geurstoffen. Dit onderwerp van de relatie tussen dermale en inhalatoire chemische allergie zal in de komende periode nader onderzocht worden in een pilot dierexperiment met twee geurstoffen. De groep 'geurproducten' zoals besproken in dit rapport omvat alle consumentenproducten die specifiek en alleen bedoeld zijn om een aangename geur te verspreiden in leefruimtes. Bijvoorbeeld ook geurkaarsen en wierook vallen hieronder. Uit een eerste inventarisatie is een enorme varieteit in het commerciele aanbod van geurproducten gebleken. De chemische samenstellingevan deze producten is complex en nadere kwantitatieve informatie over die samenstelling is vaak moeilijk te achterhalen. Ook door deze beperking is het volledig in kaart brengen van de risico's van alle stoffen in alle soorten geurproducten op dit moment niet mogelijk. Op basis van de beschikbare kennis wordt volstaan met enkele algemene aanbevelingen over waar men in de risico-evaluatie van een bepaald geurproduct op dient te letten.

Er is momenteel onvoldoende kennis beschikbaar om vast te stellen of consumenten allergische klachten aan luchtwegen kunnen krijgen als zij allergene geurstoffen in consumentenproducten inademen. Dit blijkt uit onderzoek van het RIVM, in opdracht van de nieuwe Voedsel en Waren Autoriteit (nVWA). Geurstoffen komen voor in diverse consumentenproducten voor, zoals parfums en verzorgingsproducten en schoonmaakmiddelen. Van 26 geurstoffen is bekend dat ze een huidallergie kunnen veroorzaken. Een productinventarisatie van het RIVM heeft aangetoond dat bijna al deze 26 allergene geurstoffen eveneens gebruikt worden in luchtverfrissers. Consumenten worden hierbij dus ook via de ademhaling blootgesteld aan deze geurstoffen. Onbekend is echter of deze vorm van blootstelling allergische reacties in de luchtwegen kan veroorzaken. Er zijn namelijk geen valide methoden beschikbaar om dit gezondheidsrisico vast te stellen. Bovendien zijn de gehaltes van de geurstoffen in de producten niet bekend, zodat het onmogelijk is om een schatting van de mate van blootstelling te maken. Wel tonen inhalatiestudies met muizen die het RIVM heeft uitgevoerd aan dat een van vijf onderzochte allergene geurstoffen een ongewenst effect op het immuunsysteem van de luchtwegen lijkt te hebben. Of dat ook een risico vormt voor de consument is nog niet duidelijk. Daarnaast zijn er geringe aanwijzingen dat mensen die tijdens hun werk langdurig allergene geurstoffen inademen allergische luchtwegklachten ontwikkelen.

Background and aim Unhealthy eating habits such as unhealthy food choices or overeating increase the prevalence of obesity, diabetes, cancer, cardiovascular and other diseases. Therefore, it is important to understand how separate factors, such as sensory processes, influence our eating behaviour. As one of the sensory modalities, olfaction has a relationship with food intake regulation. Previous research reveals that food odours can induce both appetite and satiation. In this thesis, we split appetite and satiation into a ‘general’ part and a ‘food specific’ part. General appetite and general satiation refer to the desire to eat in general. General satiation measured by subjective ratings (e.g. by using line scales) is also named ‘subjective satiation’. The specific part refers to the desire to eat a specific food: e.g. the appetite for a banana or the appetite for tomato soup. The main objective of this thesis was to investigate under which circumstances odours are appetizing or satiating in order to identify factors that influence our eating behaviour.Odours arrive at the odour receptors via two routes: the orthonasal route via the nose to perceive the outside world or retronasally via the mouth to ‘taste’ the food. The appetizing and satiating effects of ortho- and retronasally smelled odours were investigated by varying the odour exposure time, the odour concentration(retronasal only), the odour type, passive versus active sniffing (orthonasal only) and by switching between odour types. Methods We conducted six within-subject experiments. All participants were healthy normal-weight women (age 18-45 y and BMI 18.5-26 kg/m2). In four experiments (studies 2A, 2B, 3A and 3B), we investigated the appetizing and satiating effects of orthonasal odours, with two experiments addressing odours that were smelled passively in rooms with ambient odours (chapter 2) and two addressing actively smelled odours by sniffing the contents of a cup (chapter 3). In studies 2A (passive, n=21), 2B (passive, n=13) and 3A (active, n=61), we investigated the effects of exposure timeand odour typeon appetite, the appetite for specific foods, food preference and food intake. Differences between passiveand active exposure were investigated by comparing the data from 2A and 3A. In the fourth experiment (n=30) using a similar set-up, sweet and savoury odours were presented directly after each other, to explore the effects of daily encounters with a variety of food odours (i.e. switching). In all orthonasal studies, general appetite and the appetite for specific foods were monitored over time, using visual analogue scales. General appetite comprised hunger and desire-to-eat ratings. The appetite for specific products addressed the appetite for smelled products and the appetites for a set of other products that were congruent and incongruent with the odour (studies 2A, 2B, 3A and 3B). Food preference was assessed using a computerised program offering pairs of food pictures (studies 2A, 2B and 3B). Furthermore, two experiments addressed the satiating effects of retronasal odours while consuming tomato soup ad libitum (studies 4A and 4B). The retronasal odour exposure was disconnected from the soup base consumptionby use of a retronasal tube that was connected to an olfactometer. The odours were delivered directly into the nasal cavity at the moment a sip of soup base was swallowed. In study 4A (n=38), the satiating effects of odour exposure time(3 and 18 s) and odour concentration(5x difference) were investigated. In study 4B(n=42),we investigated whether addition of cream odourto tomato soup, in combination with a low or high viscosity, affected satiation. Hunger and appetite ratings were monitored over time during odour exposure, by using 100 mm visual analogue scales (VAS). Results The results showed that orthonasalexposure to food odours influenced the appetite for specific foods via a typical pattern: the appetite ratings for the smelled foods increased by +6-20 mm(SSA; all P

Background and aim Unhealthy eating habits such as unhealthy food choices or overeating increase the prevalence of obesity, diabetes, cancer, cardiovascular and other diseases. Therefore, it is important to understand how separate factors, such as sensory processes, influence our eating behaviour. As one of the sensory modalities, olfaction has a relationship with food intake regulation. Previous research reveals that food odours can induce both appetite and satiation. In this thesis, we split appetite and satiation into a ‘general’ part and a ‘food specific’ part. General appetite and general satiation refer to the desire to eat in general. General satiation measured by subjective ratings (e.g. by using line scales) is also named ‘subjective satiation’. The specific part refers to the desire to eat a specific food: e.g. the appetite for a banana or the appetite for tomato soup. The main objective of this thesis was to investigate under which circumstances odours are appetizing or satiating in order to identify factors that influence our eating behaviour.Odours arrive at the odour receptors via two routes: the orthonasal route via the nose to perceive the outside world or retronasally via the mouth to ‘taste’ the food. The appetizing and satiating effects of ortho- and retronasally smelled odours were investigated by varying the odour exposure time, the odour concentration(retronasal only), the odour type, passive versus active sniffing (orthonasal only) and by switching between odour types. Methods We conducted six within-subject experiments. All participants were healthy normal-weight women (age 18-45 y and BMI 18.5-26 kg/m2). In four experiments (studies 2A, 2B, 3A and 3B), we investigated the appetizing and satiating effects of orthonasal odours, with two experiments addressing odours that were smelled passively in rooms with ambient odours (chapter 2) and two addressing actively smelled odours by sniffing the contents of a cup (chapter 3). In studies 2A (passive, n=21), 2B (passive, n=13) and 3A (active, n=61), we investigated the effects of exposure timeand odour typeon appetite, the appetite for specific foods, food preference and food intake. Differences between passiveand active exposure were investigated by comparing the data from 2A and 3A. In the fourth experiment (n=30) using a similar set-up, sweet and savoury odours were presented directly after each other, to explore the effects of daily encounters with a variety of food odours (i.e. switching). In all orthonasal studies, general appetite and the appetite for specific foods were monitored over time, using visual analogue scales. General appetite comprised hunger and desire-to-eat ratings. The appetite for specific products addressed the appetite for smelled products and the appetites for a set of other products that were congruent and incongruent with the odour (studies 2A, 2B, 3A and 3B). Food preference was assessed using a computerised program offering pairs of food pictures (studies 2A, 2B and 3B). Furthermore, two experiments addressed the satiating effects of retronasal odours while consuming tomato soup ad libitum (studies 4A and 4B). The retronasal odour exposure was disconnected from the soup base consumptionby use of a retronasal tube that was connected to an olfactometer. The odours were delivered directly into the nasal cavity at the moment a sip of soup base was swallowed. In study 4A (n=38), the satiating effects of odour exposure time(3 and 18 s) and odour concentration(5x difference) were investigated. In study 4B(n=42),we investigated whether addition of cream odourto tomato soup, in combination with a low or high viscosity, affected satiation. Hunger and appetite ratings were monitored over time during odour exposure, by using 100 mm visual analogue scales (VAS). Results The results showed that orthonasalexposure to food odours influenced the appetite for specific foods via a typical pattern: the appetite ratings for the smelled foods increased by +6-20 mm(SSA; all P

Vermindering van het suikergehalte van voedingsmiddelen en dranken is met geuren te compenseren. TIFN, WUR en NIZO food research deden onderzoek naar appelsap. Optimalisatie van de combinatie van geurstoffen die van nature in het product voorkomen (clean label!) maakte een suikerreductie van 12% mogelijk zonder dat het sap minder zoet smaakte

Plaagwantsen zoals behaarde wants en brandnetelwants vormen in teelten als aubergine, komkommer en chrysant een serieus probleem. Ze geven al in kleine aantallen flinke schade: bloemabortie in aubergine, stengel- en vruchtschade in komkommer en splitkoppen in chrysant. Zodra telers wantsen of wantsenschade signaleren zien ze zich al snel genoodzaakt in te grijpen met middelen die schadelijk zijn voor aanwezige biologische bestrijders tegen andere plagen; het begin van het einde van hun biologie.

Het onderzoek naar ammoniakemissie is ongeveer acht jaar oud. Het begon met het zoeken naar een speld in de mestput. Dat bleek een dure speld te zijn. Inmiddels kunnen we zeggen dat het Varkensproefbedrijf een gouden greep gedaan heeft door goedkope en eenvoudige systemen te ontwikkelen

M.i.v. 1998 moeten vleeseenden in stallen zijn gehuisvest. Op verzoek van de gemeenten Harderwijk en Ermelo is de geur-emissie van eenden bij stalhuisvesting met mechanische ventilatie vastgesteld.

Het identificeren van belangrijke geurcomponenten van voedingsmiddelen met behulp van gaschromatografie

In dit rapport worden de emissiemetingen van ammoniak, geur, fijn stof, methaan en lachgas gerapporteerd, die in het kader van het hiervoor genoemde onderzoeksprogramma uitgevoerd zijn op het melkveehouderijbedrijf van Mts. Mensonides te Cornwerd (ligboxenstal met het vrijekeuze systeem). Het beoogde emissiereducerende principe van dit systeem is gebaseerd op 1) het afsluiten van de mestkelder door gebruik te maken van sleufvloer zonder gaatjes in de lange looppaden in de lengterichting van de stal, 2) het versneld afvoeren van de emitterende bron (urine) naar de kelder, het verschuiven van het chemisch evenwicht door het verlagen van de pH van de urine op de roostervloer, en luchtuitwisseling tussen de stal en de kelder beperken door op de verbindingspaden loodrecht op de sleufvloer en de wachtruimte vóór de melkrobots rubber matten op de roostervloer en afdichtflappen in de roosterspleten te plaatsen, en 3) door het ventilatieniveau te beperken door gebruik te maken van Automatically Controlled Natural Ventilation.

This study reports the emissions of ammonia, odour, fine dust (PM10 and PM2.5), methane and nitrous oxide from a loose housing dairy cattle barn with cubicles using the "freedom of choice" concept.

The study of the role of chemical information in species interactions has been mostly restricted to studies at the level of individual organisms. The central question in this thesis is how intraspecific chemical information conveyance and exploitation thereof by a natural enemy affects the spatial population dynamics of a species. To answer this question, I developed a spatio-temporal model where both host and parasitoid can respond to infochemicals. Our model system consists of the fruit fly Drosophila melanogaster, and its natural enemy, the larval parasitoid Leptopilina heterotoma. D. melanogaster uses its aggregation pheromone in combination with odours from fermenting fruits to localise suitable resources for reproduction. L. heterotoma uses these same odours to localise its host. For D. melanogaster, aggregation on a resource can be beneficial when a population is small and has to overcome negative effects associated with low population densities. Such negative effects, known as the Allee effect, can for instance be caused by difficulties in resource exploitation or in finding a mate. Aggregation also involves costs. Individuals within an aggregation frequently experience more severe competition for food, space and mates than they would experience when being on their own. Furthermore, I investigated which behavioural decisions enhance the ability to find - and distinguish between – odour sources that differ in their suitability for reproduction. On the individual level, this research showed that, like real fruit flies, the modelled fruit flies need to have a preference for the presence of both aggregation pheromone and food odours, over food odours alone, to be able to distinguish between the two types of odour sources. The results show that this stronger preference does not have to be innate. As long as fruit flies are able to remember and adjust their current preference based on the odour concentrations that they perceive, more fruit flies find the more attractive odour source. On a population level, this thesis shows that the use of chemical information by D. melanogaster affects its population dynamics. In the absence of its natural enemy, and when the Drosphila population is small, the use of food odours and aggregation pheromone has a positive effect on population growth and enhances the fruit fly’s colonization ability. When the population becomes larger, however, the negative effects of larval competition are stronger than the positive effects of reduced mortality due to the Allee effect. The use of chemical information was crucial to colonize an area from the boundaries. A fruit fly population that was unable to use chemical information could not colonize the area and went extinct. When parasitoids can use chemical information, parasitism rates are higher, resulting in a slower population growth of their host. No difference was recorded in fruit fly population size and in larval mortality due to parasitism, when parasitoids exploited the aggregation pheromone of the fruit fly adults as compared with the simulations where the parasitoids could only respond to chemicals emitted by the host habitat. In contrast, the use of chemical information by the host enhanced its population growth and enabled it to survive, even at higher parasitoid densities. This research showed that mortality when the population was small had a greater impact on population size than mortality due to competition or parsitism. Food patches are not always abundant in nature. Thus, the reproductive success of fruit flies is mainly determined by their opportunities of producing clutches (i.e. locating patches) rather than by preventing over-aggregation or parasitism. As a result, the use of chemical information has a net positive effect on fruit fly population dynamics, despite the fact that L. heterotoma is able to exploit it.

This study reports the emissions of ammonia, odour, fine dust (PM10 and PM2.5), methane and nitrous oxide from a loose housing dairy cattle barn with cubicles provided with a slatted floor with a rubber top layer. In dit onderzoek zijn de emissies bepaald van ammoniak, geur, fijn stof (PM10, PM2,5), methaan en lachgas uit een ligboxenstal voor melkvee met roostervloer voorzien van een bolle rubberen toplaag op het melkveehouderijbedrijf van Mts. Bijma te Augustinusga.

In dit rapport worden de emissiemetingen van ammoniak, geur, fijn stof, methaan en lachgas gerapporteerd, die zijn uitgevoerd op het melkveehouderijbedrijf van Mts. Van de Streek te Broek (ligboxenstal met het vrijekeuze systeem). Het beoogde emissiereducerende principe van dit systeem is gebaseerd op 1) het afsluiten van de mestkelder door gebruik te maken van sleufvloer zonder gaatjes in de lange looppaden in de lengterichting van de stal, 2) het versneld afvoeren van de emitterende bron (urine) naar de kelder, het verschuiven van het chemisch evenwicht door het verlagen van de pH van de urine op de roostervloer, en luchtuitwisseling tussen de stal en de kelder beperken door op de verbindingspaden loodrecht op de sleufvloer en de wachtruimte vóór de melkrobots rubber matten op de roostervloer en afdichtflappen in de roosterspleten te plaatsen, en 3) door het ventilatieniveau te beperken door gebruik te maken van Automatically Controlled Natural Ventilation (ACNV).

The performance of two experimental air scrubber was investigated during 9 months on two broiler houses. The inlet ventilation air of the houses is led through a subsoil heat exchanger. In this report the removal efficiencies of the scrubber are reported for ammonia, odour and fine dust (PM10 and PM2.5).

This study reports the emissions of ammonia, odour, fine dust (PM10 and PM2.5), methane and nitrous oxide from a loose housing dairy cattle barn with cubicles provided with a slatted floor with a rubber top layer and rubber flaps between the slats. In dit onderzoek zijn de emissies bepaald van ammoniak, geur, fijn stof (PM10, PM2,5), methaan en lachgas uit een ligboxenstal voor melkvee met roostervloer voorzien van een bolle rubberen toplaag en afdichtflappen in de roosterspleten op het melkveehouderijbedrijf van Mts. Hans en Jan Hettinga te It Heidenskip.