Background
malaria
MALARIA, RESIDUAL, ENGORGEMENT
Controlling malaria vectors in sub-Saharan Africa is a daunting task, and is now made more difficult with the development of pyrethroid resistance. The slow pace of bringing new insecticides to market requires new thinking around insecticide delivery to target indoor-biting The forerunner of DWL, insecticide-treated plastic sheeting (ITPS), was first developed in emergency settings where insecticidal materials were needed for displaced persons [To extend the ITPS concept to permanent communities, insecticidal materials were developed to cover walls and reduce entry by mosquitoes while maintaining airflow. These materials are distinct from ITPS and are referred hereafter to as DWL. DWL can be deployed by homeowners in a variety of ways, and can be thought of as household improvement, a mosquito control approach with a longstanding body of research [Although the use of insecticidal materials as eave and wall coverings is not comprehensively studied, the existing data suggests that DWL deployed to intercept mosquitoes during entry through eaves and to cover walls will kill mosquitoes during both host-seeking and indoor resting phases of blood feeding. Mosquitoes attempting to enter a DWL-protected house may: (1.) fail to enter due to the mechanical barrier on the eaves; (2.) enter the house through openings, but receive a dose of insecticide during an exploratory period; or (3.) enter the house, bite an occupant and rest on the insecticidal wall covering, thereby receiving a lethal dose of insecticide. Covering indoor surfaces with insecticidal materials exploits resting behaviour following a blood meal; contact with insecticidal materials on walls and ceilings is likely in the hours following engorgement. DWL deployed as a wall covering and eave covering, with minimal places of entry, function similarly to LLINs by preventing biting and exposing mosquitoes to insecticides during host-seeking; the treated surfaces function like Indoor Residual Spraying (IRS) by placing insecticide on indoor surfaces where mosquitoes are likely to rest.Before the current study was implemented, a deltamethrin-impregnated shade cloth DWL similar to that used in Mozambique [