Repellency of live potted plants against Anopheles gambiae from human baits in semi-field experimental huts

The repellency of potted plants against the malaria vector Anopheles gambiae sensu stricto Giles was quantified in experimental huts under semi-field conditions inside a screen-walled greenhouse. Ocimum americanum Linnaeus (Labiatae), Lantana camara L. (Verbenaceae), and Lippia uckambensis Spreng (Verbenaceae) repelled at an average of 39.7% (95% confidence interval [CI] = 29.6-48.4%), 32.4% (95% CI = 19.7-43.1%), and 33.3% (95% CI = 21.5-43.3%) of the mosquitoes, respectively (P < 0.0001 for all treatments). This was determined by logistic regression, allowing for variations associated with different bait hosts, sampling huts, and replicate test nights. In contrast, Ocimum kilimandscharicum Guerke (Labiatae), Ocimum suave Willd. (Labiatae), Corymbia citriodora Hook (Myrtaceae), Azadirachta indica A. Juss (Meliaceae), Tagetes minuta L. (Asteraceae), and Hyptis suaveolens Poit. (Lamiaceae) did not significantly repel mosquitoes. The combination of O. americanum with either L. camara or L. uckambensis repelled 31.6% (95% CI = 19.7-41.7%) and 45.2% (95% CI = 34.7-54.0%) of the mosquitoes, respectively (P < 0.0001 for both treatments). This study is the first to show that live intact plants can reduce domestic exposure to malaria vector mosquitoes. As such, they may represent a new, sustainable and readily applicable malaria vector control tool for incorporation into integrated vector management programs.