Prospects for the Development of Odour Baits to Control the Tsetse Flies Glossina tachinoides and G. palpalis s.l. J. B. Rayaisse 1 , I. Tirados 2 , D. Kaba 3 , S. Y. Dewhirst 4 , J. G. Logan 4 , A. Diarrassouba 3 , E. Salou 1 , M. O. Omolo 5,6 , P. Solano 7 , M. J. Lehane 8 *, J. A. Pickett 4 , G. A. Vale 2 , S. J. Torr 2 , J. Esterhuizen 8 1 Centre International de Recherche-De ´veloppement sur l’Elevage en zone Subhumide (CIRDES), Bobo-Dioulasso, Burkina Faso, 2 Natural Resource Institute, University of Greenwich, Chatham, Kent, United Kingdom, 3 Institut Pierre Richet, Abidjan, Co ˆ te d’Ivoire, 4 Rothamsted Research, Harpenden, United Kingdom, 5 International Center for Insect Physiology and Ecology, Nairobi, Kenya, 6 Masinde Muliro University of Science & Technology, Kakamega, Kenya, 7 IRD, UMR 177 IRD/CIRAD, CIRDES, Bobo- Dioulasso, Burkina Faso, 8 Liverpool School of Tropical Medicine, United Kingdom Abstract Field studies were done of the responses of Glossina palpalis palpalis in Co ˆte d’Ivoire, and G. p. gambiensis and G. tachinoides in Burkina Faso, to odours from humans, cattle and pigs. Responses were measured either by baiting (1.) biconical traps or (2.) electrocuting black targets with natural host odours. The catch of G. tachinoides from traps was significantly enhanced (,5 6 ) by odour from cattle but not humans. In contrast, catches from electric targets showed inconsistent results. For G. p. gambiensis both human and cattle odour increased (.2 6 ) the trap catch significantly but not the catch from electric targets. For G. p. palpalis, odours from pigs and humans increased (,5 6 ) the numbers of tsetse attracted to the vicinity of the odour source but had little effect on landing or trap-entry. For G. tachinoides a blend of POCA (P = 3-n-propylphenol; O = 1-octen-3- ol; C = 4-methylphenol; A = acetone) alone or synthetic cattle odour (acetone, 1-octen-3-ol, 4-methylphenol and 3-n- propylphenol with carbon dioxide) consistently caught more tsetse than natural cattle odour. For G. p. gambiensis, POCA consistently increased catches from both traps and targets. For G. p. palpalis, doses of carbon dioxide similar to those produced by a host resulted in similar increases in attraction. Baiting traps with super-normal (,500 mg/h) doses of acetone also consistently produced significant but slight (,1.6 6 ) increases in catches of male flies. The results suggest that odour- baited traps and insecticide-treated targets could assist the AU-Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) in its current efforts to monitor and control Palpalis group tsetse in West Africa. For all three species, only ,50% of the flies attracted to the vicinity of the trap were actually caught by it, suggesting that better traps might be developed by an analysis of the visual responses and identification of any semiochemicals involved in short-range interaction. Citation: Rayaisse JB, Tirados I, Kaba D, Dewhirst SY, Logan JG, et al. (2010) Prospects for the Development of Odour Baits to Control the Tsetse Flies Glossina tachinoides and G. palpalis s.l.. PLoS Negl Trop Dis 4(3): e632. doi:10.1371/journal.pntd.0000632 Editor: Joseph Mathu Ndung’u, Foundation for Innovative New Diagnostics (FIND), Switzerland Received June 26, 2009; Accepted January 28, 2010; Published March 16, 2010 Copyright: ß 2010 Rayaisse et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This project was supported by funding from the Bill & Melinda Gates Foundation and the EU INCO-DEV program. Rothamsted Research receives grant- aided support from the Biotechnology and Biological Sciences Research Council (BBSRC) of the United Kingdom. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: m.j.lehane@liv.ac.uk Introduction Tsetse flies (Diptera: Glossinidae) infest ,10 million km 2 of sub-Saharan Africa where they transmit trypanosomes which cause Human African Trypanosomiasis (HAT; also known as sleeping sickness) and African Animal Trypanosomiasis (AAT; also known as Nagana). This complex of diseases has an important impact on health and productivity in sub-Saharan Africa [1,2]. HAT occurs in two forms; ‘‘rhodesiense’’ which is caused by Trypanosoma brucei rhodesiense and occurs in eastern and southern Africa; ‘‘gambiense’’ which is caused by T. b. gambiense and occurs in western and central Africa. Currently the latter causes ,97% of the total number of reported cases of HAT [1] and is transmitted in West Africa by tsetse of the Palpalis group where the most dangerous species are G. palpalis s.l. and G. tachinoides. Means of tackling HAT and AAT differ fundamentally. Control of AAT transmitted by riverine flies is funded and implemented largely by livestock keepers [3] who treat their livestock with trypanocides and insecticides and/or deploy odour- baited traps or targets to control tsetse. Control of HAT is managed and funded by intergovernmental and national agencies and, in the case of the gambiense form, relies mainly on systematic screening, treatment and follow-up of millions of human individuals across the affected region [1]. With a few local exceptions [4] vector control has generally played little role in the management of HAT over the past 80 years. Paradoxically, vector control could contribute significantly to the management of HAT. The relatively low infection rates (,0.1%) and long incubation period (,25 days) of T. brucei spp. in the vector [5], compared to the Trypanosoma spp. of veterinary importance, means that comparable reductions in the density and life- expectancy of tsetse populations would have a relatively greater effect on HAT than AAT. A cost-effective method of tsetse control that could be implemented by local people would complement the efforts of agencies that support mass screening and treatment and hence improve sustainability. Analyses of the history of efforts against sleeping sickness reveal that sustainable solutions have proved elusive [6,7]. An integrated approach, based on a combination of interventions directed at both tsetse and trypanosomes, may provide a better way forward. www.plosntds.org 1 March 2010 | Volume 4 | Issue 3 | e632