Protecting cows in small holder farms in East Africa from tsetse flies by mimicking the odor profile of a non-host bovid

<div><p>Background</p><p>For 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 (<i>Glossina</i> spp.), vectors of African trypanosomosis, causing nagana, repellents more powerful than plant derived, from a non-host animal the waterbuck, <i>Kobus ellipsiprymnus defassa</i>, 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.</p><p>Methodology/Principal findings</p><p>To 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.</p><p>Conclusion/Significance</p><p>Clear 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—<i>‘cows in waterbuck clothing’</i>.</p></div

Average number of <i>G</i>. <i>pallidipes</i> flies caught per trap per day (apparent densities) with various tsetse repellent (WRC) treatments over the trial period.

<p>Average number of <i>G</i>. <i>pallidipes</i> flies caught per trap per day (apparent densities) with various tsetse repellent (WRC) treatments over the trial period.</p

Trypanosome infection in cattle with waterbuck repellent compounds (WRC).

<p>Estimates obtained from the generalized estimating equations model. The 95% Confidence Intervals (CI) were constructed using empirically corrected standard errors.</p

Repellent dispenser developed to deliver waterbuck repellent compounds for cattle.

<p>(a) Dispenser with protective shield and (b) without protective shield to show tubing from which the repellent compounds are released and (c) a cow with a repellent collar.</p

Cattle with repellent collars grazing in bush with natural tsetse challenge.

<p>(Picture R.K. Saini).</p

Farmers perceptions of the effectiveness of the new repellent collar technology.

<p>Farmers perceptions of the effectiveness of the new repellent collar technology.</p

Target used to attract and kill the flies (pull).

<p>(Picture R.K. Saini).</p

Non-participating farmers’ grazing practices that take advantage of cattle protected with repellent collars.

<p>Non-participating farmers’ grazing practices that take advantage of cattle protected with repellent collars.</p

Map showing experimental sites in SHGR and location of households which provided cattle for the trial.

<p>Map showing experimental sites in SHGR and location of households which provided cattle for the trial.</p

Waterbuck <i>Kobus ellipsiprymnus defassa</i> Rüppel (Bovidae).

<p>(Picture R.K. Saini).</p