Eave tubes for malaria control in Africa: prototyping and evaluation against Anopheles gambiae s.s. and Anopheles arabiensis under semi-field conditions in western Kenya

Abstract

BackgroundWhilst significant progress has been made in the fight against malaria, vector control continues to rely on just two insecticidal methods, i.e., indoor residual spraying and insecticidal bed nets. House improvement shows great potential to complement these methods and may further reduce indoor mosquito biting and disease transmission. Open eaves serve as important mosquito house entry points and provide a suitable location for intercepting host-seeking anophelines. This study describes semi-field experiments in western Kenya with eave tubes, a household protection product that leverages the natural behaviour of host-seeking malaria mosquitoes.MethodsSemi-field experiments were conducted in two screen-houses. In both of these a typical western Kenyan house, with mud walls and corrugated iron sheet roofing, was built. Eave tubes with bendiocarb- or deltamethrin-treated eave tube inserts were installed in the houses, and the impact on house entry of local strains of Anopheles gambiae and Anopheles arabiensis was determined. Experiments with open eave tubes (no netting) were conducted as a control and to determine house entry through eave tubes. Insecticidal activity of the inserts treated with insecticide was examined using standard 3-min exposure bioassays.ResultsExperiments with open eave tubes showed that a high percentage of released mosquitoes entered the house through tubes during experimental nights. When tubes were fitted with bendiocarb- or deltamethrin-treated inserts, on average 21% [95% CI 18–25%] and 39% [CI 26–51%] of An. gambiae s.s. were recaptured the following morning, respectively. This contrasts with 71% [CI 60–81%] in the treatment with open eaves and 54% [CI 47–61%] in the treatment where inserts were treated with fluorescent dye powder. For An. arabiensis recapture was 21% [CI 14–27%] and 22% [CI 18–25%], respectively, compared to 46% [CI 40–52%] and 25% [CI 15–35%] in the treatments with open tubes and fluorescent dye.ConclusionsInsecticide-treated eave tubes resulted in significant reductions in recapture rates for both malaria vector species, representing the first and promising results with this novel control tool against Kenyan malaria vectors. Further field evaluation of eave tubes under more realistic field conditions, as well as their comparison with existing approaches in terms of cost-effectiveness and community acceptance, is called for.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-017-1926-5) contains supplementary material, which is available to authorized users.

Screening and field performance of powder-formulated insecticides on eave tube inserts against pyrethroid resistant Anopheles gambiae s.l.: an investigation into ‘actives’ prior to a randomized controlled trial in Côte d’Ivoire

“…gambiae mosquitoes. Although the mortality observed in the experimental huts is consistent with findings from previous studies [ 8 , 9 ], mortality was much higher in laboratory bioassays. This could be either due to a percentage of mosquitoes not entering the tubes over the course of the night or that contact with the treated inserts was too transient for the mosquito to pick up a lethal dose of insecticide.…”

“…Eave tube inserts that fit into locally produced PVC tubes have been designed with electrostatic netting attached to a polyethylene frame consisting of a plastic circle with six spokes and a central protruding node (see [ 9 ] for images of the insert design). The frame provides physical support to the netting and allows easy insertion inside eave tubes.…”

Semi-field studies to better understand the impact of eave tubes on mosquito mortality and behaviour

“…This coating provides a long-lasting static charge that enables insecticide powders to bind to the netting. The inserts block the entry of mosquitoes while contact with the netting leads to transfer of insecticidal particles onto the mosquito body [ 4 , 5 ]. The dose transferred is sufficiently high that lethal doses of insecticide can be delivered during transient contact, even when the mosquitoes are classified as ‘resistant’ to the active ingredient [ 4 , 5 ].…”

Community knowledge and perceptions on malaria prevention and house screening in Nyabondo, Western Kenya

“…Other studies in the Gambia, Guinea, Tanzania and Ethiopia have shown that house screening is a potential, sustainable and effective intervention in preventing mosquito entry into houses [5, 10, 12–16]. In related studies in Western Kenya, house modifications involving insect screen ceilings made from locally available materials and use of insecticide-treated eave tubes resulted in significant reductions in human exposure to malaria vectors representing the first and promising results with this novel control tool against malaria vectors [13, 17].…”