title: Responses of Glossina pallidipes and Glossina morsitans morsitans tsetse flies to analogues of δ-octalactone and selected blends.
abstract: Previous studies have shown that δ-octalactone is an important component of the tsetse-refractory waterbuck (Kobus defassa) repellent odour blend. In the present study, structure-activity comparison was undertaken to determine the effects of the length of the side chain and ring size of the lactone on adult Glossina pallidipes and Glossina morsitans morsitans. The responses of the flies to each compound were studied in a two-choice wind tunnel. Increasing the chain length from C3 (δ-octalactone) to C4 (δ-nonalactone) enhanced repellency to both species (G. pallidipes from 60.0 to 72.0%, and G. m. morsitans from 61.3 to 72.6%), while increasing the ring size from six (δ-octalactone) to seven members (ε-nonalactone) changed the activity from repellency to attraction that was comparable to that of the phenolic blend associated with fermented cow urine (p>0.05). Blending δ-nonalactone with 4-methylguaiacol (known tsetse repellent) significantly (p<0.05) raised repellency to 86.7 and 91.7% against G. pallidipes and G. m. morsitans respectively. Follow-up Latin Square Designed field studies (Shimba hills in coastal areas in Kenya) with G. pallidipes populations confirmed the higher repellence of δ-nonalactone (with/without 4-methylguaiacol) compared to δ-octalactone (also, with/without 4-methylguaiacol). The results show that subtle structural changes of olfactory signals can significantly change their interactions with olfactory receptor neurons, and either shift their potency, or change their activity from repellence to attraction. Our results also lay down useful groundwork in the development of more effective control of tsetse by 'push', 'pull' and 'push-pull' tsetse control tactics.
authors.affiliation: Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
authors.forename: Benson M
authors.initials: BM
authors.lastname: Wachira
authors.affiliation: Biotechnology Research Institute-Kenya Agricultural and Livestock Research Organization, P.O. Box 362-00902 Kikuyu, Kenya; Department of Biochemistry, Pwani University Health Research Institute (PUHRI), P. O. Box. 195-80108, Kilifi Kenya, Kenya. Electronic address: mireji@gmail.com.
authors.forename: Paul O
authors.initials: PO
authors.lastname: Mireji
authors.affiliation: Biotechnology Research Institute-Kenya Agricultural and Livestock Research Organization, P.O. Box 362-00902 Kikuyu, Kenya.
authors.forename: Sylvance
authors.initials: S
authors.lastname: Okoth
authors.affiliation: Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Ng'ang'a
authors.affiliation: Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
authors.forename: Julius M
authors.initials: JM
authors.lastname: William
authors.affiliation: Biotechnology Research Institute-Kenya Agricultural and Livestock Research Organization, P.O. Box 362-00902 Kikuyu, Kenya.
authors.forename: Grace A
authors.initials: GA
authors.lastname: Murilla
authors.affiliation: Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hassanali
mesh_terms: D000818:Animals; D002020:Buffaloes / Q000469:parasitology; D006790:Host-Parasite Interactions; D007302:Insect Repellents / Q000737:chemistry*; D007630:Kenya; D009812:Odorants; D014370:Tsetse Flies / Q000145:classification / Q000502:physiology*
chemical_list: D007302:Insect Repellents
keywords: Attraction; Glossina morsitans morsitans; Glossina pallidipes; Lactones; Repellency; Structure-activity