Efficacy of 3D screens for sustainable mosquito control: a semi-field experimental hut evaluation in northeastern Tanzania

Abstract

Background: A three-dimensional window screen (3D-Screen) has been developed to create a window double-screen trap (3D-WDST), effectively capturing and preventing the escape of mosquitoes. A 2015 laboratory study demonstrated the 3D-Screen's efficacy, capturing 92% of mosquitoes in a double-screen setup during wind tunnel assays. To further evaluate its effectiveness, phase II experimental hut trials were conducted in Muheza, Tanzania.

Methods: Three experimental hut trials were carried out between 2016 and 2017. Trial I tested two versions of the 3D-WDST in huts with open or closed eaves, with one version using a single 3D-Screen and the other using two 3D-Screens. Trial II examined the 3D-WDST with two 3D-Screens in huts with or without baffles, while Trial III compared handmade and machine-made 3D structures. Mosquito capturing efficacy of the 3D-WDST was measured by comparing the number of mosquitoes collected in the test hut to a control hut with standard exit traps.

Results: Trial I showed that the 3D-WDST with two 3D-Screens used in huts with open eaves achieved the highest mosquito-capturing efficacy. This treatment captured 33.11% (CI 7.40-58.81) of female anophelines relative to the total collected in this hut (3D-WDST and room collections) and 27.27% (CI 4.23-50.31) of female anophelines relative to the total collected in the control hut (exit traps, room, and verandahs collections). In Trial II, the two 3D-Screens version of the 3D-WDST captured 70.32% (CI 56.87-83.77) and 51.07% (CI 21.72-80.41) of female anophelines in huts with and without baffles, respectively. Compared to the control hut, the capturing efficacy for female anophelines was 138.6% (37.23-239.9) and 42.41% (14.77-70.05) for huts with and without baffles, respectively. Trial III demonstrated similar performance between hand- and machine-made 3D structures.

Conclusions: The 3D-WDST proved effective in capturing malaria vectors under semi-field experimental hut conditions. Using 3D-Screens on both sides of the window openings was more effective than using a single-sided 3D-Screen. Additionally, both hand- and machine-made 3D structures exhibited equally effective performance, supporting the production of durable cones on an industrial scale for future large-scale studies evaluating the 3D-WDST at the community level.

Keywords: 3D-Screens; 3D-WDST; Anopheles; Experimental huts; Malaria; Mosquito control; Muheza; Northeastern Tanzania; Window double screens.

Fig. 1

Three-dimensional cone architecture, design, and unidirectional entry mechanism to capture mosquitoes

Fig. 2

A 3D-Screen on one side (facing outside) and a traditional screen on the other side (facing inside) to form a 3D-WDST with a single 3D-Screen

Fig. 3

Three-dimensional screens on both sides (facing outside and inside) to form 3D-WDST with two 3D screens

Fig. 4

East African experimental huts. A Six experimental huts in Muheza, northeastern Tanzania. B Experimental hut design showing overall architecture of the hut, mosquito entry and exit point, and placement of window traps (exit traps are shown)

Fig. 5

Top view of experimental hut showing the four verandas

Fig. 6

3D-Screen installation in experimental huts with open and closed eave configurations. A 3D-WDST with a single 3D-Screen and open eaves, B 3D-WDST with a single 3D-Screen and closed eaves, C 3D-WDST with two 3D-Screens and open eaves, D 3D-WDST with two 3D-Screens and closed eaves. E An example of closed eaves in one of the experimental huts, F an example of open eaves with 3D-WDST fixed on an experimental hut window

Fig. 7

3D-WDST with two 3D-Screens installed on experimental huts with baffles. A 3D-WDST with baffles included, B baffles setup in one of the experimental huts

Fig. 8

A Weekly hut rotation plan. B Field worker collecting trapped mosquitoes from the 3D-WDST

Fig. 9

Weekly anopheline count in each treatment (each point represents mean mosquito number collected during the 6-week collection period). A Weekly mean anopheline collection from the treatment huts. B Weekly mean anopheline collection from the 3D-WDST from each treatment hut. DC: double 3D-Screen and closed eaves, DO: double 3D-Screens and open eaves, SC: single 3D-Screen and closed eaves, SO: single 3D-Screen and open eaves

Fig. 10

Nightly mosquito counts for different treatment conditions during 30-day collection period. DC: double 3D-Screen and closed eaves, DO: double 3D-Screens and open eaves, SC: single 3D-Screen and closed eaves, SO: single 3D-Screen and open eaves

Fig. 11

Weekly mosquito count in the huts with and without baffles (each point represents mean mosquito number collected during the 6-week collection period). A Weekly mean female anopheline collection from the huts with and without baffles. B Weekly mean female anopheline collection from the 3D-WDST from huts with and without baffles. C Weekly mean female culicine collection from the huts with and without baffles. D Weekly mean female culicine collection from the 3D-WDST from huts with and without baffles

Fig. 12

Nightly mosquito counts from T_open and T_baffles conditions during 36-day collection period

Fig. 13

Weekly mosquito count in four different hut conditions (each point represents mean mosquito number collected during the 6-week collection period). A Weekly mean female anopheline collection from the treatment huts. B Weekly mean female anopheline collection from the 3D-WDST of each hut condition. C Weekly mean female culicine collection from the treatment huts. D Weekly mean female culicine collection from the 3D-WDST of each hut condition

Fig. 14

Nightly mosquito counts from different hut conditions during 36-day collection period