Abstract
BackgroundRecent malaria vector control measures have considerably reduced indoor biting mosquito populations. However, reducing the outdoor biting populations remains a challenge because of the unavailability of appropriate lures to achieve this. This study sought to test the efficacy of plant-based synthetic odor baits in trapping outdoor populations of malaria vectors.Methodology and Principal FindingThree plant-based lures ((E)-linalool oxide [LO], (E)-linalool oxide and (E)-β-ocimene [LO + OC], and a six-component blend comprising (E)-linalool oxide, (E)-β-ocimene, hexanal, β-pinene, limonene, and (E)-β-farnesene [Blend C]), were tested alongside an animal/human-based synthetic lure (comprising heptanal, octanal, nonanal, and decanal [Blend F]) and worn socks in a malaria endemic zone in the western part of Kenya. Mosquito Magnet-X (MM-X) and lightless Centre for Disease Control (CDC) light traps were used. Odor-baited traps were compared with traps baited with either solvent alone or solvent + carbon dioxide (controls) for 18 days in a series of randomized incomplete-block designs of days × sites × treatments. The interactive effect of plant and animal/human odor was also tested by combining LO with either Blend F or worn socks. Our results show that irrespective of trap type, traps baited with synthetic plant odors compared favorably to the same traps baited with synthetic animal odors and worn socks in trapping malaria vectors, relative to the controls. Combining LO and worn socks enhanced trap captures of Anopheles species while LO + Blend F recorded reduced trap capture. Carbon dioxide enhanced total trap capture of both plant- and animal/human-derived odors. However, significantly higher proportions of male and engorged female Anopheles gambiae s.l. were caught when the odor treatments did not include carbon dioxide.Conclusion and SignificanceThe results highlight the potential of plant-based odors and specifically linalool oxide, with or without carbon dioxide, for surveillance and mass trapping of malaria vectors.
Highlights
Malaria continues to be a leading cause of mortality and morbidity in sub-Saharan Africa, with the latest global estimates documenting about 219 million cases in 2010 and an estimated death toll of 1.24 million [1,2]
The results highlight the potential of plant-based odors and linalool oxide, with or without carbon dioxide, for surveillance and mass trapping of malaria vectors
Interactive effect of plant and human/animal related odors. In another set of experiments, we evaluated the interactive effect of plant and animal/human odors by comparing the trapping efficacy of LO, Blend F, socks, LO + Blend F, and LO + socks either with or without CO2 in MM-X traps
Summary
Malaria continues to be a leading cause of mortality and morbidity in sub-Saharan Africa, with the latest global estimates documenting about 219 million cases in 2010 and an estimated death toll of 1.24 million [1,2]. The development of an effective vaccine has been hampered by the complexity of the parasite and its life cycle [7,8], extensive antigenic variation [9], and a poor understanding of the interaction between Plasmodium falciparum and the human immune system [10]. In view of this situation, a multifaceted approach to malaria control is advocated [11], with vector control forming an integral component of it [12,13,14]. This study sought to test the efficacy of plant-based synthetic odor baits in trapping outdoor populations of malaria vectors
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