Cattle-Derived Unsaturated Aldehydes Repel Biting Midges and Mosquitoes

Host-derived repellents offer a novel way to reduce disease vector-host interactions, particularly for vectors and nuisance pests where commercial repellents are not available, e.g., Culicoides biting midges. By revising the criteria previously used to identify bioactive volatile organic compounds for Culicoides nubeculosus, we identify (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, and (E)-2-nonenal to be differentially present in the headspace odour of cattle hair and to elicit antennal responses in this research model species. A blend of these unsaturated aldehydes elicited an aversive response in C. nubeculosus, as well as a repellent response in three disease vector mosquito species, Aedes aegypti, Culex quinquefasciatus and Anopheles coluzzii, a response that was stronger than that to the commercially available repellents tested (DEET, IR3535, PMD, icaridin, and d-allethrin). Culicoides nubeculosus was behaviourally indifferent to these commercially available repellents tested, except d-allethrin to which it was attracted. The identification of a host-derived repellent odour blend, which reduces the interaction between biting midges extends the array of tools to be used in integrated vector management of these and other disease vectors

Identification of host volatiles and their role in the behavioural modulation of host-seeking Culicoides biting midges

Culicoides biting midges are important vectors of Bluetongue and Schmallenberg viruses in Europe. The introduction of these viruses highlighted the need to develop novel surveillance and control tools to monitor and manage biting midges. Biting midges, as most insects, primarily use olfactory cues to recognize and discriminate resources for their survival and reproduction. Blood feeding insects rely on host-derived volatiles to locate their vertebrate hosts, and these odours can be exploited to manipulate insect-host interaction. The primary goal of this thesis was to identify host volatiles that modulate the host-seeking behaviour of biting midges. Through coupled gas chromatography and electroantennographic detection (GC-EAD) analysis of odour collections from cattle hair and urine, I identified several compounds that, in combination with carbon dioxide, elicited behavioural attraction or inhibition in Culicoides nubeculosus, in a dose dependent manner. Some of these host odours were evaluated in the field showing similar behavioural responses of C. impunctatus. Both laboratory and field assays emphasized the importance of release rate to obtain optimal behavioural responses. The impact of using host volatiles to monitor host-seeking biting midges was shown in another study. Here, I showed that incandescent light traps baited with two cattle kairomones, 1-octen-3-ol and carbon dioxide, caught significantly more insects than UV light traps. UV light traps are to date the most commonly used method for monitoring biting midges. That said, differences were observed between trap types, both concerning species composition and the physiological state of the female biting midges caught. Incorporating the novel bioactive compounds, formulated in blends and released in proper ratio and rate, could further increase the efficacy of this trapping method. By incorporating these attractants together with repellent compounds identified in this project, a "push-pull"- system for biting midges could also be envisioned. The host volatiles identified are detected by the peripheral olfactory system of biting midges. A comparative analysis across biting species with different host preferences revealed a correlation between host preference and the number and types of antennal and maxillary palp sensilla. Functional characterisation of these sensillum types will be the next step to increase our understanding of how host odours are detected by biting midges With this thesis I have increased our understanding of the chemical ecology of host-seeking female biting midges and their peripheral olfactory system. Future research projects will need to develop viable commercial products that could be incorporated into management strategies for Culicoides biting midges

Identification of cattle-derived volatiles that modulate the behavioral response of the biting midge culicoides nubeculosus

Identification of host-derived volatiles is an important step towards the development of novel surveillance and control tools for Culicoides biting midges. In this study, we identified compounds from headspace collections of cattle hair and urine that modulate the behavioral response of Culicoides nubeculosus, a research model species with a similar host-range as the vectors of Bluetongue disease and Schmallenberg disease in Europe. Combined gas chromatography and electroantennographic detection (GC-EAD) analysis revealed 23 bioactive compounds, of which 17, together with octanal, were evaluated in a two-choice behavioral assay in the presence of CO2. Decanal, 2-phenylethanal, 1-octen-3-ol, 2-ethylhexanol, 3-methylindole, phenol, and 3-ethylphenol elicited attraction of host seeking C. nubeculosus, whereas heptanal, octanal, nonanal, 3-propylphenol, and 4-propylphenol inhibited the insects’ attraction to CO2, when compared to CO2 alone. 6-Methyl-5-hepten-2-one, 3-methylphenol, 4-methylphenol, and 4-ethylphenol elicited both attraction and inhibition. The behavioral responses were dependent on the concentration tested. Our results show that cattle-derived odors have the potential to be used for the manipulation of the behavior of Culicoides biting midges

The chemical code for attracting Culex mosquitoes

Mosquitoes use chemical codes to locate and discriminate among vertebrate hosts to obtain a blood meal. Recent advances have allowed for the identification of the chemical codes used by mosquitoes to locate and discriminate humans from other vertebrate hosts. Humans are incidental "dead-end" hosts for the West Nile virus, which is maintained in an enzootic cycle, primarily through its transmission between infected birds by Culex mosquitoes. Host-seeking Culex mosquitoes are attracted to the odor of chicken, which are used in sentinel traps to monitor West Nile virus transmission. Using combined gas chromatography and electroantennography and mass spectrometry we identify a blend of volatile organic compounds present in chicken emanates, including mostly salient bioactive compounds previously identified in human emanates. When released at their identified ratios, this blend elicits behavioral responses of Culex pipiens molestus and Culex quinquefasciatus similar to that to the natural chicken odor. Tested under field conditions, this blend attract Culex spp. and other species of mosquitoes using birds among their hosts. This study provides evidence for conserved chemical codes for resource location by mosquitoes, and highlights the intricate role of CO2 for host-seeking mosquitoes. The identification of conserved chemical codes, which drive innate preference behaviors that are fundamental for survival and reproduction, provides important substrates for future control interventions targeting disease vector mosquitoes

Evaluation of host-derived volatiles for trapping Culicoides biting midges (Diptera: Ceratopogonidae)

Culicoides biting midges (Diptera: Ceratopognidae) cause pain and distress through blood feeding, and transmit viruses that threaten both animal and human health worldwide. There are few effective tools for monitoring and control of biting midges, with semiochemical-based strategies offering the advantage of targeting host-seeking populations. In previous studies, we identified the host preference of multiple Culicoides species, including Culicoides impunctatus, as well as cattle-derived compounds that modulate the behavioral responses of C. nubeculosus under laboratory conditions. Here, we test the efficacy of these compounds, when released at different rates, in attracting C. impunctatus under field conditions in Southern Sweden. Traps releasing 1-octen-3-ol, decanal, phenol, 4-methylphenol or 3-propylphenol, when combined with carbon dioxide (CO2), captured significantly higher numbers of C. impunctatus compared to control traps baited with CO2 alone, with low release rates (0.1 mg h−1, 1 mg h−1) being generally more attractive. In contrast, traps releasing octanal or (E)-2-nonenal at 1 mg h−1 and 10 mg h−1 collected significantly lower numbers of C. impunctatus than control traps baited with CO2 only. Nonanal and 2-ethylhexanol did not affect the attraction of C. impunctatus when compared to CO2 alone at any of the release rates tested. The potential use of these semiochemicals as attractants and repellents for biting midge control is discussed

Upplevelsen av anställningsrelationen under en outsourcingprocess

This study explores employees subjective experience of their employment relation before and during an outsourcing process and has its starting point in the concept of the psychological contract. Eight employees, in the process of being outsourced, were interviewed. The focus was on ‘the employees’ individual experiences and stories about the subjective and perceived employment relationship. Data were analyzed using basic qualitative analysis. The results indicate that a perceived breach of the psychological contract had a profound negative impact on the employment relationship and caused profound negative attitudes and emotional reactions towards the employer. The importance of a well established and mutually formulated psychological contract for the parties involved in the employment relationship, and in an extended perspective for the organization as such, is discussed