Modified veranda‐trap hut for improved evaluation of vector control interventions

Oxborough, RM; Kitau, Jovin; Mosha, Frank; Rowland, Mark

doi:10.1111/mve.12123

Cited by 9 publications

(8 citation statements)

References 27 publications

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“…Ideally, next-generation tracking systems are interlinked with ambient weather data in order to correct for prevailing airflows on the actual airspeed and flight direction of the mosquito. Further developments in tracking techniques could reduce the need for specially constructed experimental houses and enhance knowledge of free-flying mosquitoes [ 15 , 45 ] to improve vector intervention tools.…”

Section: Discussionmentioning

confidence: 99%

“…Studies on mosquito house entry often describe the approach and entry of indoor-biting mosquitoes based on catches with traps that can intercept house entry or exit behaviours [ 5 , 12 , 13 ]. These studies are based on the knowledge that anopheline mosquitoes predominantly enter and exit via eaves [ 14 , 15 ]. An extensive field study on An.…”

Section: Introductionmentioning

confidence: 99%

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Visualization of house-entry behaviour of malaria mosquitoes

Spitzen

Koelewijn

Mukabana

et al. 2016

Malar J

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BackgroundMalaria mosquitoes often blood feed indoors on human hosts. The mosquitoes predominantly enter houses via open eaves. Host-seeking is odour-driven, and finding a host depends on the quality of the odour plume and whether the route towards the host is free of obstructions. Little is known about in-flight behaviour of mosquitoes during house entry. This semi-field study visualizes mosquito house entry in three dimensions (3D) and offers new insights for optimizing vector control interventions.MethodsThe approach and house entry of Anopheles gambiae sensu stricto was studied in a semi-field set-up using video-recorded flight tracks and 3D analysis. Behavioural parameters of host-seeking female mosquitoes were visualized with respect to their position relative to the eave as well as whether a mosquito would enter or not. Host odour was standardized using an attractive synthetic blend in addition to CO2. The study was conducted in western Kenya at the Thomas Odhiambo Campus of the International Centre of Insect Physiology and Ecology, Mbita.ResultsThe majority of host-seeking An. gambiae approached a house with a flight altitude at eave level, arriving within a horizontal arc of 180°. Fifty-five per cent of mosquitoes approaching a house did not enter or made multiple attempts before passing through the eave. During approach, mosquitoes greatly reduced their speed and the flight paths became more convoluted. As a result, mosquitoes that passed through the eave spent more than 80 % of the observed time within 30 cm of the eave. Mosquitoes that exited the eave departed at eave level and followed the edge of the roof (12.5 %) or quickly re-entered after exiting (9.6 %).ConclusionsThe study shows that host-seeking mosquitoes, when entering a house, approach the eave in a wide angle to the house at eave level. Less than 25 % of approaching mosquitoes entered the house without interruption, whereas 12.5 % of mosquitoes that had entered left the house again within the time of observation. Advances in tracking techniques open a new array of questions that can now be answered to improve household interventions that combat malaria transmission.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1293-7) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Visualization of house-entry behaviour of malaria mosquitoes

Spitzen

Koelewijn

Mukabana

et al. 2016

Malar J

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“…This allowed mosquitoes to freely enter huts through all four eave spaces so the impact of partial eave blocking (only one eave left open) with ITWL could be assessed for some treatments. Inwardly directed eave baffles were installed to prevent egress of mosquitoes that had entered the hut; the only route of exiting was through the window traps [ 32 , 33 ] (Fig. 1 ).…”

Section: Methodsmentioning

confidence: 99%

Experimental hut evaluation of a novel long-lasting non-pyrethroid durable wall lining for control of pyrethroid-resistant Anopheles gambiae and Anopheles funestus in Tanzania

Malima

Emidi

Messenger

et al. 2017

Malar J

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BackgroundA novel, insecticide-treated, durable wall lining (ITWL), which mimics indoor residual spraying (IRS), has been developed to provide prolonged vector control when fixed to the inner walls of houses. PermaNet® ITWL is a polypropylene material containing non-pyrethroids (abamectin and fenpyroximate) which migrate gradually to the surface.MethodsAn experimental hut trial was conducted in an area of pyrethroid-resistant Anopheles gambiae s.l. and Anopheles funestus s.s. to compare the efficacy of non-pyrethroid ITWL, long-lasting insecticidal nets (LLIN) (Interceptor®), pyrethroid ITWL (ZeroVector®), and non-pyrethroid ITWL + LLIN.ResultsThe non-pyrethroid ITWL produced relatively low levels of mortality, between 40–50% for An. funestus and An. gambiae, across all treatments. Against An. funestus, the non-pyrethroid ITWL when used without LLIN produced 47% mortality but this level of mortality was not significantly different to that of the LLIN alone (29%, P = 0.306) or ITWL + LLIN (35%, P = 0.385). Mortality levels for An. gambiae were similar to An. funestus with non-pyrethroid ITWL, producing 43% mortality compared with 26% for the LLIN. Exiting rates from ITWL huts were similar to the control and highest when the LLIN was present. An attempt to restrict mosquito access by covering the eave gap with ITWL (one eave open vs four open) had no effect on numbers entering. The LLIN provided personal protection when added to the ITWL with only 30% blood-fed compared with 69 and 56% (P = 0.001) for ITWL alone. Cone bioassays on ITWL with 30 min exposure after the trial produced mortality of >90% using field An. gambiae. ConclusionsDespite high mortality in bioassays, the hut trial produced only limited mortality which was attributed to pyrethroid resistance against the pyrethroid ITWL and low efficacy in the non-pyrethroid ITWL. Hut ceilings were left uncovered and may have served as a potential untreated refuge. By analogy to IRS campaigns, which also do not routinely treat ceilings, high community coverage with ITWL may still reduce malaria transmission. Restriction of eave gaps by 75% proved an inadequate barrier to mosquito entry. The findings represent the first 2 months after installation and do not necessarily predict long-term efficacy.

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“…Ideally, next-generation tracking systems are interlinked with ambient weather data in order to correct for prevailing airflows on the actual airspeed and flight direction of the mosquito. Further developments in tracking techniques could reduce the need for specially constructed experimental houses and enhance knowledge of free-flying mosquitoes (Andriessen et al, 2015;Oxborough et al, 2015) to improve vector intervention tools.…”

Section: Discussionmentioning

confidence: 99%

“…Studies on mosquito house entry often describe the approach and entry of indoorbiting mosquitoes based on catches with traps that can intercept house entry or exit behaviours (Gillies, 1955;Grieco et al, 2000;Ogoma et al, 2010). These studies are based on the knowledge that anopheline mosquitoes predominantly enter and exit via eaves (Oxborough et al, 2015;Snow, 1987). An extensive field study on An.…”

Section: House Entrymentioning

confidence: 99%

Keeping track of the enemy : Flight analyses of the host-seeking malaria mosquito Anopheles gambiae s.s

Spitzen

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Female mosquitoes can transmit pathogens to their host during blood feeding and are an important vector of human diseases such as dengue, chikungunya, filariasis and malaria. After 15 years of decline in the number of fatal malaria cases, this decline came to a halt in 2016. Growing resistance against drugs and insecticides pose a serious threat for future human health. This thesis focuses on the behaviour of host-seeking malaria mosquitoes by analysing their flight paths during their approach to different host cues. Fundamental knowledge on the role of selected host cues was acquired. In addition, studies to support successful implementation of vector control interventions were performed in both windtunnel settings and the semi-field in Kenya. My research demonstrates that automated tracking systems can strengthen behavioural-ecological studies on disease vectors, in addition to conventional bio-assays such as olfactometers, by providing detailed information on the approach behaviour of mosquitoes to different targets. The attraction towards the host-sensory cue CO 2 was investigated in an olfactometer bioassay. Trap catches of female Anopheles gambiae s.s. were enhanced by separation of the CO 2 source from the source of human skin emanations. Close-range deterrent effects of CO 2 were overcome by the simultaneous presence of skin emanations. Flight path analysis of mosquitoes in a wind tunnel, showed that exposure to human odour resulted in prolonged and highly convoluted flight tracks. The combination of odour with heat was crucial to induce landings of host-seeking mosquitoes. A semifield study in Kenya revealed that house-entering mosquitoes approached the eave of a house in a wide angle to the house at eave level, where the proportion that entered uninterruptedly (23%) spent just a few seconds around the eave area. The presence of insecticide-treated nets inside a house did not repel mosquitoes as measured by the number of house entries. At close range, in a wind tunnel, free-flight exposure of mosquitoes to deltamethrin-treated nets in combination with human odour did not reveal any (excito-) repellent effect and resulted in lower mortality rates compared to standard bioassays where contact with the treated material is enforced. The knowledge obtained on the behavioural responses of mosquitoes to host cues has indirectly affected vector control tool implementations in the field. For example, in the development of an odour-baited trap, a CO 2 release pipe was included that is separated from the attractive odour plume. The role of heat was exploited in the development of a repellent bioassay and a heat source was added to another trap model. Insights in house-entry behaviour and mosquito responses to bed nets support the successful implementation of push-pull systems, installation of eave tubes or implementing house improvement operations to reduce malaria transmission. An integrated vector management approach is required to further develop existing control tools by adding and improving alternative interven...

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Modified veranda‐trap hut for improved evaluation of vector control interventions

Cited by 9 publications

References 27 publications

Visualization of house-entry behaviour of malaria mosquitoes

Visualization of house-entry behaviour of malaria mosquitoes

Experimental hut evaluation of a novel long-lasting non-pyrethroid durable wall lining for control of pyrethroid-resistant Anopheles gambiae and Anopheles funestus in Tanzania

Keeping track of the enemy : Flight analyses of the host-seeking malaria mosquito Anopheles gambiae s.s

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