Plant products used as mosquito repellents in Guinea Bissau, West Africa.

By standardized interviews of people in 23 rural villages, in the Oio region of Guinea Bissau, we collected data on which plant species and plant derived products or methods people use to reduce mosquito biting activity. The following plants were used to reduce numbers of mosquitoes indoors at night: fresh or smouldering Hyptis suaveolens Poit. (Lamiaceae), smoke of the bark of Daniellia oliveri Rolfe (Caesalpiniaceae), smoke of the infructescence of Elaeis guineensis Jacq. (Arecaceae), smoke of the seed capsules of Parkia biglobosa (Jacq.) Benth. (Mimosaceae), smoke of the leaves of Azadirachta indica A.Juss. (Meliaceae) and Eucalyptus sp. (Myrtaceae), fresh Ocimum canum Sims (Lamiaceae), and fresh Senna occidentalis (L.) Link (Caesalpiniaceae). In two field experiments we estimated the 'repellent activity' of certain of these plants and compared their efficacies with those of two commercially available mosquito repellents, i.e. 'positive' controls. In the first experiment we tested: smouldering H. suaveolens (85.4% repellency); fresh H. suaveolens (73.2%); burning of the bark of D. oliveri (74.7%); and smoke of the leaves of Eucalyptus (72.2%). In the second experiment we tested: smouldering H. suaveolens (83.6% repellency); fresh H. suaveolens (66.5%); burning of the bark of D. oliveri (77.9%); smoke of the leaves of A. indica (76.0%); smoke of the infructescence of E. guineensis (69.0%); fresh O. canum (63.6%); and fresh S. occidentalis; (29.4%). All the products tested, except S. occidentalis were significantly more effective than the negative control.