title: Spectrum of metabolic-based resistance to DDT and pyrethroids in Anopheles gambiae s.l. populations from Cameroon.
abstract: Some populations of Anopheles gambiae s.l. from Cameroon were reported to develop resistance to DDT or pyrethroids but were free of the kdr mutation "Leucine-Phenylalanine" (Leu-Phe). This study reports on the metabolic activity of non-specific esterases (NSEs), mixed function oxidases (MFOs), and glutathione S-transferases (GSTs), three enzyme systems commonly involved in insecticide resistance. Biochemical assays were performed in DDT or pyrethroid-resistant populations of An. gambiae s.l. from Douala, Mbalmayo, Pitoa, and Simatou neighborhoods. Enzyme activity was compared to the Kisumu-susceptible reference strain using the Mann-Whitney test. Most of the tested samples had elevated NSE activity (P < 0.02). The Douala sample evenly displayed elevated GST activity (P < 0.001), while high MFO level was recorded in the Pitoa sample (P < 0.001). MFO or GST levels were sometimes lower or similar to that of the Kisumu strain. These results suggest metabolic detoxification is a major DDT or pyrethroid resistance mechanism and emphasize the need for further investigations on An. gambiae s.l. resistance mechanisms in Cameroon.
authors.affiliation: Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, BP 288, Yaoundé, Cameroon.
authors.forename: Josiane
authors.initials: J
authors.lastname: Etang
authors.forename: Lucien
authors.initials: L
authors.lastname: Manga
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Toto
authors.forename: Pierre
authors.initials: P
authors.lastname: Guillet
authors.forename: Etienne
authors.initials: E
authors.lastname: Fondjo
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chandre
mesh_terms: D000818:Animals; D000852:Anopheles / Q000254:growth & development / Q000378:metabolism*; D002163:Cameroon; D003634:DDT / Q000633:toxicity*; D004950:Esterases / Q000378:metabolism; D005843:Geography; D005982:Glutathione Transferase / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000633:toxicity; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011722:Pyrethrins / Q000633:toxicity*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D003634:DDT; D006899:Mixed Function Oxygenases; D005982:Glutathione Transferase; D004950:Esterases