4 years ago

Evaluating Putative Repellent 'Push' and Attractive 'Pull' Components for Manipulating the Odour-orientation of Host-seeking Malaria Vectors in the Peri-domestic Space

Margaret Mendi Njoroge, Ulrike Fillinger, Adam Saddler, Sarah Moore, Willem Takken, Joop van Loon, Alexandra Hiscox

Background Novel malaria vector control approaches aim to combine tools to work in synergy for maximum protection. This study aimed to evaluate novel and re-evaluate existing, putative repellent 'push' and attractive 'pull' components for manipulating the odour-orientation of malaria vectors in the peri-domestic space.

Methods Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (1) test the efficacy of citriodiol or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (2) understand the efficacy of an MB5-baited Suna-trap in attracting vectors in the presence of a human being; (3) assess 2-butanone as a CO2 replacement for trapping; and (4) determine the protection provided by a full push-pull set up. The air-concentrations of the chemical constituents of the push-pull mosquito control tool were quantified.

Results Microencapsulated citriodiol eave strips did not provide any outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips significantly reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12-0.23). This impact was lower (OR 0.59; 95% CI 0.52-0.66) during the push-pull experiment which was associated with low night-time temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being, however, with a human volunteer in the same system, the trap caught less than 1% of all released mosquitoes. The volunteer consistently attracted overtwo-thirds of all mosquitoes released. This was the case in the absence ('pull' only) and in the presence of a spatial repellent ('push-pull'), indicating that in its current configuration the tested 'pull' does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 metres from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction.

Conclusion This step-by-step evaluation of the selected 'push' and 'pull' components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector Anopheles arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control. 

Publisher URL: https://www.researchsquare.com/article/rs-76654/latest

DOI: 10.21203/rs.3.rs-76654/v1

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