A blinded, controlled trial of an ultrasound device as mosquito repellent

Ultrasound emitting devices are used to repel mosquitoes. We tested the rep elling properties of a commercially available ultrasound device in a domest ic setting in Gabon. Devices emitting three different block frequencies ran ging from 3 to 11 kHz were tested in a paired, cross-over blinded and place bo controlled trial during eighteen nights in nine pairs of houses. A total of 7485 mosquitoes (10% Anopheles, 62% Culex, 27% Mansonia and 1% Aedes) w ere caught, 23 per house per night. There was no significant difference in landing rate between the houses with ultrasound device and the houses with placebo for any species of mosquito. Thus the ultrasound device used was no t effective against mosquitoes in this strictly controlled trial.