Background
Methods
Study area
Experimental hut
Experiment arms
Washing, cone-bioassays and chemical analysis
Selection of volunteers
Hut acclimatization and suitability
Evaluation in experimental huts
Rotation of arms and volunteers
Mosquito collection
Chemical analysis for active ingredient content in net samples
Data analysis
Results
Hut suitability
Species composition
Arms | Untreated polyester net | Unwashed Olyset Net | Conventionally treated polyester net | Olyset Net washed 20 times | Olyset Plus washed 20 times | Unwashed Olyset Plus |
---|---|---|---|---|---|---|
Number of collections | 72 | 72 | 72 | 72 | 72 | 72 |
Number of females entered/caught | 303 | 49 | 41 | 54 | 36 | 32 |
Number of females caught per night | 4.2a
| 0.7b
| 0.6b
| 0.8b
| 0.5b
| 0.4b
|
Deterrence in % (95 % CI) | – | 83.8a (79.7, 88.0) | 86.5a (82.6, 90.3) | 82.2a (77.9, 86.5) | 88.1a (84.5, 91.8) | 89.4a (86.0, 92.9) |
Exit rate in % (95 % CI) | 44.2a (38.6, 49.8) | 69.4b (56.5, 82.3) | 82.9b (71.4, 94.4) | 70.4b (58.2, 82.5) | 77.8b (64.2, 91.4) | 56.3ab (39.1, 73.4) |
Blood feeding in % (95 % CI) | 77.6a (72.9, 82.3) | 26.5b (14.2, 38.9) | 7.3b (1.5, 19.9)* | 29.6b (17.5, 41.8) | 30.6b (15.5, 45.6) | 18.8b (5.2, 32.3) |
Blood feeding inhibition in % (95 % CI) | – | 65.9a (45.3, 78.6) | 90.6a (71.9, 96.8) | 61.9a (42.1, 74.8) | 60.6a (35.3, 76.0) | 75.8a (50.1, 88.3) |
Total mortality in % (95 % CI) | 2.0a (0.4, 3.5) | 100.0b (100, 100) | 100.0b (100, 100) | 96.3b (87.2, 99.6)* | 97.2b (85.5, 99.9)* | 100.0b (100, 100) |
Variables | Untreated polyester neta
| Unwashed Olyset Net | Conventionally treated polyester net | Olyset Net washed 20 times | Olyset Plus washed 20 times | Unwashed Olyset Plus |
---|---|---|---|---|---|---|
Entry (deterrence) | ||||||
IRR (95 % CI) | 1.0 | 0.16 (0.10–0.26) | 0.14 (0.08–0.22) | 0.18 (0.11–0.28) | 0.12 (0.07–0.20) | 0.11 (0.06–0.18) |
Z | −7.61 | −8.08 | −7.33 | −8.38 | −8.61 | |
P | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
Exit (induced exophily) | ||||||
Odds ratio (95 % CI) | 1.0 | 2.86 (1. 50–5.47) | 6.13 (2.63–14.25) | 2.99 (1.60–5.61) | 4.41 (1.95–10.00) | 1.62 (0.78–3.38) |
Wald statistics | 10.08 | 17.70 | 11.78 | 12.66 | 1.67 | |
P | 0.001 | <0.001 | 0.001 | <0.001 | 0.197 | |
Blood feeding (inhibition) | ||||||
Odds ratio (95 % CI) | 1.0 | 0.10 (0.05–0.21) | 0.02 (0.01–0.08) | 0.12 (0.06–0.23) | 0.13 (0.06–0.27) | 0.07 (0.03–0.17) |
Wald statistics | 41.25 | 37.72 | 41.12 | 28.34 | 32.69 | |
P | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
Total mortality (killing) | ||||||
Odds ratio (95 % CI) | 1.0 |
b
|
b
| 1287.0 (252.9–6550.3) | 1732.5 (202.7–14810.7) |
b
|
Wald statistics | 74.38 | 46.40 | ||||
P | <0.001 | <0.001 |
Entry
Exit
Blood feeding
Mortality
Residual activity of the insecticide on the nets
Sl no | Arms | Before any wash | After 20 washes | Prior to hut evaluation | After hut evaluation | ||||
---|---|---|---|---|---|---|---|---|---|
NE | CM (%) | NE | CM (%) | NE | CM (%) | NE | CM (%) | ||
1 | Untreated polyester net | 50 | 0 | 50 | 0 | 50 | 2 | 50 | 4 |
2 | Unwashed Olyset Net | 50 | 100 | – | – | 50 | 100 | 50 | 100 |
3 | Polyester net conventionally treated, washed until just before exhaustion | 50 | 100 | 50 | 82a (4 washes) | 50 | 86 | 50 | 96 |
4 | Olyset Net washed 20 times | 50 | 100 | 50 | 62 | 50 | 100 | 50 | 100 |
5 | Olyset Plus LLIN washed 20 times | 50 | 100 | 50 | 90 | 50 | 100 | 50 | 100 |
6 | Unwashed Olyset Plus LLIN | 50 | 100 | – | – | 50 | 100 | 50 | 100 |
Insecticide content
Treatment | Before washing | After washing | AI retention (% of wash 0) | After testing |
---|---|---|---|---|
Permethrin content (g/kg) | ||||
Unwashed Olyset Net | 19.94 | – | – | 19.34 |
Olyset Net washed 20 times | 20.01 | 17.68 | 88 % | 17.58 |
Unwashed Olyset Plus LLIN | 19.13 | – | – | 17.64 |
Olyset Plus LLIN washed 20 times | 18.82 | 14.11 | 75 % | 13.75 |
Polyester net conventionally treated, washed until just before exhaustion | 15.33 | 11.36 | 74 % | 10.42 |
Untreated polyester net | <1 | <1 | – | <1 |
Piperonyl butoxide content (g/kg) | ||||
Unwashed Olyset Net | <1 | <1 | – | <1 |
Olyset Net washed 20 times | <1 | <1 | – | <1 |
Unwashed Olyset Plus LLIN | 9.02 | – | – | 8.26 |
Olyset Plus LLIN washed 20 times | 8.79 | 3.96 | 45 % | 3.84 |
Polyester net conventionally treated, washed until just before exhaustion | <1 | <1 | – | <1 |
Untreated polyester net | <1 | <1 | – | <1 |