Field efficacy of thermally expelled or live potted repellent plants against African malaria vectors in western Kenya.

Abstract

To estimate the effectiveness of live potted plants and thermal expulsion of plant materials in repelling African malaria vectors in traditional houses in western Kenya. Ocimum americanum, Lantana camara and Lippia ukambensis were tested in live, intact potted form whereas leaves of Corymbia citriodora, leaves and seeds of O. kilimandscharicum and O. suave were tested by thermal expulsion from modified traditional stoves. A latin square design was applied for randomly assigning the treatment and control plants to experimental houses over different nights. All plant species showed significant repellency against Anopheles gambiae sensu lato Giles (Diptera: Culicidae) (81.5%An. arabiensis Patton and 18.5%An. gambiae sensu stricto Giles), the main vectors of malaria in Africa, with the highest repellency by C. citriodora (48.71%, P < 0.0001) followed by an equal level of repellency of O. kilimandscharicum and O. suave (44.54%, P = 0.001) during application of plant material by thermal expulsion. All three plant species also showed a residual effect against An. gambiae s.l. with 36-44% repellency post-application period (22.30-06.30 hours) after a period of thermal expulsion. Similarly, intact potted plants of O. americanum and L. camara repelled An. gambiae s.l. significantly (37.91%, P = 0.004; and 27.22%, P = 0.05, respectively). Thermal expulsion of leaves and seeds of O. kilimandscharicum significantly repelled An. funestus Giles, although none of the potted plants repelled this species. Both methods of application may offer cost-effective alternatives as additional means of household protection, and a useful complement to bed nets, particularly for the early part of the evening before bedtime.