MIDGETRAP · An innovative semiochemical based tool for monitoring and control of biting midge vectors of bluetongue and Schmallenberg disease

An innovative semiochemical based tool for monitoring and control of biting midge vectors of bluetongue and Schmallenberg disease

Field testing of cow urine as a potential midge attractant CDC insect light traps were placed in pairs on farm land sustaining populations of biting midges. One trap in each pair (designated test) was baited with 1L of cow urine. The second trap was baited with 1L distilled water (designated control). Traps were switched on approximately two hours before sunset, and switched off two hours after sunset. Three variations of the experiment were performed, of 12 pair-replicates each. 1. Both test and control traps supplemented with carbon dioxide released from a cylinder 2. Test and control traps without carbon dioxide release 3. Both traps with carbon dioxide release, but natural urine replaced with the 'phenolic fraction' of known insect attractants isolated from urine. The results of these field studies show that urine is strongly attractive to biting midges, but only when presented in combination with carbon dioxide. This will have important implications for developing any odour-based trap for use in protecting livestock from biting midges. Furthermore, this attraction was not replicated by an artificial 'phenolic fraction' of urine, comprise chemicals known to attract tsetse fly. This indicates that the full complement of chemicals responsible for eliciting the attraction of midges to urine remain to be identified. Gas-chromatography linked electroantennography (GC-EAD) to identify chemicals from urine eliciting responses in the biting midge antenna. GC-EAD performed by E. Isberg at SLU identified a number of chemicals isolated from cow urine and hair eliciting responses in midge antenna. The Fellow was trained in this technique, but was not able to improve upon the results achieved by Isberg. He was however able to assist in the analysis and presentation of the results for publication. One of the difficulties with performing GC-EAD on biting insects is that noise produced from neurones detecting movement can obscure the signal from chemical-sensory neurones. In order to identify a broader spectrum of chemicals from urine which can be detected by midges, the Scientist in Charge has trained the Fellow in a more sensitive technique, single sensillum recording (SSR). Dr Bray will continue with this work in his new position at the Natural Resources Institute, where he is in the process of setting up a SSR facility. Laboratory testing of chemicals identified from headspace of urine Y tube bioassays were carried out to measure biting midge responses to individual chemicals eliciting electrophysiological responses in GC-EAD. In the absence of artificially released carbon dioxide, no attractive response was apparent to either whole urine odour or individual chemical components. This concurs with results of field experiments, where whole urine was found to be attractive to midges only when presented in combination with carbon dioxide. Results of Y tube bioassays conducted by Isberg, and analysed by the Fellow, identified a number of chemicals from urine and cattle hair which elicited behavioural responses, when presented in combination with carbon dioxide. Both attractive and repellent activity was observed, with midge responses varying over the different concentrations of the chemicals presented. The results of these experiments have been published in Journal of Chemical Ecology. Field testing of semiochemicals eliciting responses to biting midges in the laboratory E. Isberg has carried out a number of field experiments measuring midge responses to semiochemicals identified from cattle hair and urine. The Fellow has assisted by analysing the data from these experiments. The results show that a number of the identified chemicals can increase attraction to powered traps releasing carbon dioxide. Furthermore, some of the chemicals also attract as repellents above threshold concentrations. Conclusions The principle scientific goal of this project was to determine the feasibility of using attractive odours identified from urine as a means of luring biting midges to traps in the field. Currently, there are no suitable tools for monitoring and control of these vectors of fatal animal diseases on farms. Results from both the laboratory and field have shown that urine and some individual component of urine are attractive to midges, but only in combination with release of carbon dioxide. This has important implications for development of new tools for midge control. Socio-economic impact of the project Throughout the project, we have worked closely with livestock farmers, trap producers and suppliers of tools for managing biting insects. Feedback from both farmers and suppliers of insect control products indicate there is strong demand for naturally-derived repellents for protecting animals and people. Building on our results, work is continuing at SLU with industrial partners to bring these products to market. The wider socio-economic impact is therefore that this project has facilitated in tangibly reducing 'the gap of death' between academic research and industry, thereby helping to strengthen growth within the ERA. In addition, the training provided by this project has led to the appointment of the Fellow as a permanent Senior Research Fellow at the Natural Resources Institute (UK). Dr Bray will work at the interface between academia and industry, improving global food security through application of chemical ecology. As such, the aim of this career development fellowship has been achieved, as the Fellow has now reached a position of profession maturity.

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