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Clustering of host-seeking activity of Anopheles gambiae mosquitoes at the top surface of a human-baited bed net.

Lynd A, McCall PJ - Malar. J. (2013)

Bottom Line: To confirm sticky-net reliability, the experiment was repeated using a pitched sticky-net (tilted sides converging at apex, i.e., neither horizontal nor vertical).Capture rates at horizontal and vertical surfaces were not significantly different and the sticky-net was not repellent.The results provide support for the two-in-one bed net design for managing pyrethroid-resistant vector populations.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: Knowledge of the interactions between mosquitoes and humans, and how vector control interventions affect them, is sparse. A study exploring host-seeking behaviour at a human-occupied bed net, a key event in such interactions, is reported here.

Methods: Host-seeking female Anopheles gambiae activity was studied using a human-baited 'sticky-net' (a bed net without insecticide, coated with non-setting adhesive) to trap mosquitoes. The numbers and distribution of mosquitoes captured on each surface of the bed net were recorded and analysed using non-parametric statistical methods and random effects regression analysis. To confirm sticky-net reliability, the experiment was repeated using a pitched sticky-net (tilted sides converging at apex, i.e., neither horizontal nor vertical). The capture efficiency of horizontal and vertical sticky surfaces were compared, and the potential repellency of the adhesive was investigated.

Results: In a semi-field experiment, more mosquitoes were caught on the top (74-87%) than on the sides of the net (p < 0.001). In laboratory experiments, more mosquitoes were caught on the top than on the sides in human-baited tests (p < 0.001), significantly different to unbaited controls (p < 0.001) where most mosquitoes were on the sides (p = 0.047). In both experiments, approximately 70% of mosquitoes captured on the top surface were clustered within a 90 × 90 cm (or lesser) area directly above the head and chest (p < 0.001). In pitched net tests, similar clustering occurred over the sleeper's head and chest in baited tests only (p < 0.001). Capture rates at horizontal and vertical surfaces were not significantly different and the sticky-net was not repellent.

Conclusion: This study demonstrated that An. gambiae activity occurs predominantly within a limited area of the top surface of bed nets. The results provide support for the two-in-one bed net design for managing pyrethroid-resistant vector populations. Further exploration of vector behaviour at the bed net interface could contribute to additional improvements in insecticide-treated bed net design or the development of novel vector control tools.

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Experimental set-up of semi-field and laboratory sticky-net trials. A. The set-up used in semi-field trials showing the bed and sticky-net (with 30 sq cm grid marking) in situ inside the canvas tent. B. Diagram of the grid scheme on the top surface of the standard rectangular used in laboratory sticky-net trials, and the position of the human bait beneath. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. Positions of the head/feet were reversed in each of two repeat trials for each volunteer. Mosquitoes were released at positions A or B, and the release container was located either on the floor or at the ceiling. C. Diagram of the grid numbering scheme on the side surfaces of the pitched net in relation to the human bait within. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. D. The pitched sticky-net in the climate controlled room with a human bait inside.
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Figure 1: Experimental set-up of semi-field and laboratory sticky-net trials. A. The set-up used in semi-field trials showing the bed and sticky-net (with 30 sq cm grid marking) in situ inside the canvas tent. B. Diagram of the grid scheme on the top surface of the standard rectangular used in laboratory sticky-net trials, and the position of the human bait beneath. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. Positions of the head/feet were reversed in each of two repeat trials for each volunteer. Mosquitoes were released at positions A or B, and the release container was located either on the floor or at the ceiling. C. Diagram of the grid numbering scheme on the side surfaces of the pitched net in relation to the human bait within. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. D. The pitched sticky-net in the climate controlled room with a human bait inside.

Mentions: The initial study was undertaken at CDC/KEMRI in Kisian, Kenya. Colony-reared mosquitoes were released inside a large canvas tent (3.5 × 2.5 × 2.5 m high at apex) containing the rectangular baited sticky-net (locally made untreated polyester bed net, 2.1 × 0.9 × 1.5 m high), marked with a 30 sq cm grid (Figure 1A).


Clustering of host-seeking activity of Anopheles gambiae mosquitoes at the top surface of a human-baited bed net.

Lynd A, McCall PJ - Malar. J. (2013)

Experimental set-up of semi-field and laboratory sticky-net trials. A. The set-up used in semi-field trials showing the bed and sticky-net (with 30 sq cm grid marking) in situ inside the canvas tent. B. Diagram of the grid scheme on the top surface of the standard rectangular used in laboratory sticky-net trials, and the position of the human bait beneath. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. Positions of the head/feet were reversed in each of two repeat trials for each volunteer. Mosquitoes were released at positions A or B, and the release container was located either on the floor or at the ceiling. C. Diagram of the grid numbering scheme on the side surfaces of the pitched net in relation to the human bait within. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. D. The pitched sticky-net in the climate controlled room with a human bait inside.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3733746&req=5

Figure 1: Experimental set-up of semi-field and laboratory sticky-net trials. A. The set-up used in semi-field trials showing the bed and sticky-net (with 30 sq cm grid marking) in situ inside the canvas tent. B. Diagram of the grid scheme on the top surface of the standard rectangular used in laboratory sticky-net trials, and the position of the human bait beneath. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. Positions of the head/feet were reversed in each of two repeat trials for each volunteer. Mosquitoes were released at positions A or B, and the release container was located either on the floor or at the ceiling. C. Diagram of the grid numbering scheme on the side surfaces of the pitched net in relation to the human bait within. Grid squares were 15 sq cm, except row 0 which were 7.5 × 15 cm. D. The pitched sticky-net in the climate controlled room with a human bait inside.
Mentions: The initial study was undertaken at CDC/KEMRI in Kisian, Kenya. Colony-reared mosquitoes were released inside a large canvas tent (3.5 × 2.5 × 2.5 m high at apex) containing the rectangular baited sticky-net (locally made untreated polyester bed net, 2.1 × 0.9 × 1.5 m high), marked with a 30 sq cm grid (Figure 1A).

Bottom Line: To confirm sticky-net reliability, the experiment was repeated using a pitched sticky-net (tilted sides converging at apex, i.e., neither horizontal nor vertical).Capture rates at horizontal and vertical surfaces were not significantly different and the sticky-net was not repellent.The results provide support for the two-in-one bed net design for managing pyrethroid-resistant vector populations.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: Knowledge of the interactions between mosquitoes and humans, and how vector control interventions affect them, is sparse. A study exploring host-seeking behaviour at a human-occupied bed net, a key event in such interactions, is reported here.

Methods: Host-seeking female Anopheles gambiae activity was studied using a human-baited 'sticky-net' (a bed net without insecticide, coated with non-setting adhesive) to trap mosquitoes. The numbers and distribution of mosquitoes captured on each surface of the bed net were recorded and analysed using non-parametric statistical methods and random effects regression analysis. To confirm sticky-net reliability, the experiment was repeated using a pitched sticky-net (tilted sides converging at apex, i.e., neither horizontal nor vertical). The capture efficiency of horizontal and vertical sticky surfaces were compared, and the potential repellency of the adhesive was investigated.

Results: In a semi-field experiment, more mosquitoes were caught on the top (74-87%) than on the sides of the net (p < 0.001). In laboratory experiments, more mosquitoes were caught on the top than on the sides in human-baited tests (p < 0.001), significantly different to unbaited controls (p < 0.001) where most mosquitoes were on the sides (p = 0.047). In both experiments, approximately 70% of mosquitoes captured on the top surface were clustered within a 90 × 90 cm (or lesser) area directly above the head and chest (p < 0.001). In pitched net tests, similar clustering occurred over the sleeper's head and chest in baited tests only (p < 0.001). Capture rates at horizontal and vertical surfaces were not significantly different and the sticky-net was not repellent.

Conclusion: This study demonstrated that An. gambiae activity occurs predominantly within a limited area of the top surface of bed nets. The results provide support for the two-in-one bed net design for managing pyrethroid-resistant vector populations. Further exploration of vector behaviour at the bed net interface could contribute to additional improvements in insecticide-treated bed net design or the development of novel vector control tools.

Show MeSH
Related in: MedlinePlus