Finally, and in contrast with laboratory studies, ambient climatic conditions may vary over space and time, and cause highly variable trap catches in the field. that results in strong 'competition' between odour-baited traps and human hosts present in the indoor environment, arguably always in favour of humans expressing the full range of physical and chemical cues. A third reason relates to the highly endophagic behaviour of An. Alternatively, prolonged maintenance of mosquito strains under artificial laboratory conditions may result in distorted behaviour and responses to 'attractants' that would not be similar in nature. It remains speculative why attempts to reproduce laboratory studies under field conditions have been unsuccessful to date, although the substantial differences between olfactometer-based studies and field-based trapping methods may be a prime cause for this. These comprise commonly known kairomones like carbon dioxide, but also carboxylic fatty acids, oxo-carboxylic acids, ketones, phenols, L-lactic acid, and ammonia. Of the several hundreds of volatiles produced by humans, a fair number have been reported to elicit behavioural responses by An. Identification of specific kairomones with key involvement in governing the host-seeking process has therefore been advocated. , which has been attributed to the presence of allomonal effects of breath, variability in skin microfloral composition, or both. However, humans vary substantially in their innate attractiveness towards An. Some traps use whole human odour, like the CDC light trap placed next to an occupied bednet, the OBET and Mbita traps. Studies on semiochemicals affecting its host-seeking behaviour have intensified since the late 1980s, with the main aim to replace the Human Biting Catch (HBC). is a highly anthropophilic mosquito, with a tendency to blood feed and rest inside houses. A fourth set of essentials follows, namely the cost, applicability and acceptance of such devices by end-users in anticipated market sectors.Īnopheles gambiae s.s. There are three important components of trap development, namely the 'attractant', the physical trap design, and trapping mechanism used. Such traps may find application in mosquito surveillance, risk assessment and forecasting, and/or be used en masse for population suppression and disease transmission reduction similar to trap-bait systems developed for tsetse flies. Semi-field systems offer the prospect of high-throughput screening of candidate kairomones, which may expedite the development of efficient trap-bait systems for this and other African mosquito species.ĭevelopment of odour-baited trapping devices for biting insects remains a challenge for many important species, including African malaria vectors. These results are the first to report behavioural responses of an African malaria vector to human foot odour outside the laboratory, and further investigation of fractions and/or individual chemical components of this odour complex are called for. A synergistic response (P < 0.001) was observed towards the combination of foot odour and CO 2, which increased catches of these odours alone by 3.8 and 2.7 times, respectively. Foot odour remained behaviourally active for at least 8 days after collection on nylon or cotton sock fabric. ResultsĪpart from 1-octen-3-ol, all odour baits caused significant (P < 0.05) increases in trap catches over non-baited traps. Trap catches were log (x+1) transformed and subjected to Latin square analysis of variance procedures. Traps were baited with human foot odour (collected on socks), carbon dioxide (CO 2, 500 ml min -1), ammonia (NH 3), 1-octen-3-ol, or various combinations thereof. gambiae towards odour-baited counterflow geometry traps (MM-X model American Biophysics Corp., RI) was studied in semi-field (screen house) conditions in western Kenya. A contained system, intermediate between the laboratory and open field, is presented and previous reports that human foot odour induces behavioural responses of Anopheles gambiae confirmed. A large variety of 'attractants' has been identified in laboratory investigations, yet few of these increase trap catches in the field. The successful development of odour-baited trapping systems for mosquitoes depends on the identification of behaviourally active semiochemicals, besides the design and operating principles of such devices.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |