Effect of Metofluthrin-Impregnated Spatial Repellent Devices Combined with New Long-Lasting Insecticidal Nets (Olyset® Plus) on Pyrethroid-Resistant Malaria Vectors and Malaria Prevalence: Field Trial in South-Eastern Malawi.

Long-lasting insecticidal nets (LLINs) experience some operational problems that reduce their effectiveness, such as limited spaces for hanging, biting of mosquitoes outdoors, a shift of key biting time from midnight to dawn or dusk, and development of pyrethroid resistance in mosquitoes. The concept of spatial repellency may be a countermeasure to overcome the above issues. The effect of the combined use of metofluthrin-impregnated spatial repellent devices (MSRDs) and LLINs (Olyset® Plus) on malaria prevalence and vector mosquitoes were examined in malaria endemic villages in south-eastern Malawi. The intervention reduced the infection rate in children as well as the number of pyrethroid-resistant vector mosquitoes. To achieve effective malaria control, continued intervention using MSRDs with 2 strips per 10 m2 at 3-month intervals to reduce the density of malaria mosquitoes is recommended.