Abstract
BackgroundEffective malaria vector control targeting indoor host-seeking mosquitoes has resulted in fewer vectors entering houses in many areas of sub-Saharan Africa, with the proportion of vectors outdoors becoming more important in the transmission of this disease. This study aimed to develop a gravid trap for the outdoor collection of the malaria vector Anopheles gambiae s.l. based on evaluation and modification of commercially available gravid traps.MethodsExperiments were implemented in an 80 m2 semi-field system where 200 gravid Anopheles gambiae s.s. were released nightly. The efficacy of the Box, CDC and Frommer updraft gravid traps was compared. The Box gravid trap was tested to determine if the presence of the trap over water and the trap’s sound affected catch size. Mosquitoes approaching the treatment were evaluated using electrocuting nets or detergents added to the water in the trap. Based on the results, a new gravid trap (OviART trap) that provided an open, unobstructed oviposition site was developed and evaluated.ResultsBox and CDC gravid traps collected similar numbers (relative rate (RR) 0.8, 95% confidence interval (CI) 0.6–1.2; p = 0.284), whereas the Frommer trap caught 70% fewer mosquitoes (RR 0.3, 95% CI 0.2–0.5; p < 0.001). The number of mosquitoes approaching the Box trap was significantly reduced when the trap was positioned over a water-filled basin compared to an open pond (RR 0.7 95% CI 0.6–0.7; p < 0.001). This effect was not due to the sound of the trap. Catch size increased by 60% (RR 1.6, 1.2–2.2; p = 0.001) with the new OviART trap.ConclusionGravid An. Gambiae s.s. females were visually deterred by the presence of the trapping device directly over the oviposition medium. Based on these investigations, an effective gravid trap was developed that provides open landing space for egg-laying Anopheles .
Highlights
Vector control plays a central role in the prevention of malaria [1,2,3,4,5]
The floor was covered with sand to a depth of 30 cm so that artificial aquatic habitats could be dug into the ground to simulate a natural larval habitat for the An. gambiae s.s. mosquitoes [43]
Trap comparison An. gambiae s.s. females were caught in all three traps in the semi-field system (Figure 6), but the total mean number trapped per night was low (59.3, 95% confidence intervals (CIs) 50.3–70.0) i.e.
Summary
Vector control plays a central role in the prevention of malaria [1,2,3,4,5]. Monitoring vector populations and assessment of disease risk are among the key elements of vector management strategies [6,7,8,9]. In sub-Saharan Africa (SSA) the most commonly used sampling methods for malaria vectors are human landing catches, CDC light traps, and pyrethrum spray collections which are excellent for sampling host-seeking and indoor resting mosquitoes [14,15,16]. Effective malaria vector control targeting indoor host-seeking mosquitoes has resulted in fewer vectors entering houses in many areas of sub-Saharan Africa, with the proportion of vectors outdoors becoming more important in the transmission of this disease. Gambiae s.s. females were visually deterred by the presence of the trapping device directly over the oviposition medium Based on these investigations, an effective gravid trap was developed that provides open landing space for egg-laying Anopheles
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