BackgroundFor the first time, differential attraction of pathogen vectors to vertebrate animals is investigated for novel repellents which when applied to preferred host animals turn them into non-hosts thereby providing a new paradigm for innovative vector control. For effectively controlling tsetse flies (Glossina spp.), vectors of African trypanosomosis, causing nagana, repellents more powerful than plant derived, from a non-host animal the waterbuck, Kobus ellipsiprymnus defassa, have recently been identified. Here we investigate these repellents in the field to protect cattle from nagana by making cattle as unattractive as the buck.Methodology/Principal findingsTo dispense the waterbuck repellents comprising guaiacol, geranylacetone, pentanoic acid and δ-octalactone, (patent application) we developed an innovative collar-mounted release system for individual cattle. We tested protecting cattle, under natural tsetse challenge, from tsetse transmitted nagana in a large field trial comprising 1,100 cattle with repellent collars in Kenya for 24 months. The collars provided substantial protection to livestock from trypanosome infection by reducing disease levels >80%. Protected cattle were healthier, showed significantly reduced disease levels, higher packed cell volume and significantly increased weight. Collars >60% reduced trypanocide use, 72.7% increase in ownership of oxen per household and enhanced traction power (protected animals ploughed 66% more land than unprotected). Land under cultivation increased by 73.4%. Increase in traction power of protected animals reduced by 69.1% acres tilled by hand per household per ploughing season. Improved food security and household income from very high acceptance of collars (99%) motivated the farmers to form a registered community based organization promoting collars for integrated tsetse control and their commercialization.Conclusion/SignificanceClear demonstration that repellents from un-preferred hosts prevent contact between host and vector, thereby preventing disease transmission: a new paradigm for vector control. Evidence that deploying water buck repellents converts cattle into non-hosts for tsetse flies—‘cows in waterbuck clothing’.

The presence of pheromones produced by larvae ofGlossina morsitans morsitans andG. m. centralis, respectively, which attract gravid females and result in aggregation of pupae, is confirmed. Behavioral experiments indicated that females preferred to larviposit over moist sand conditioned by previously allowing larvae to pupariate in it. Similar results were obtained with filter papers contaminated with the prepupariation excretions of larvae and with volatiles collected from larvae prior to pupariation.n-Pentadecane andn-dodecane were identified as the dominant electrophysiologically active components of the larviposition pheromones ofG. m. morsitans andG. m. centralis, respectively, by GC-EAD and GC-MS analysis of the trapped larval volatiles. Both identified compounds were shown to significantly attract gravid females to larviposition sites in laboratory behavioral assays.