Towards an Optimal Design of Target for Tsetse Control: Comparisons of Novel Targets for the Control of Palpalis Group Tsetse in West Africa

Jean Baptiste Rayaisse,Stephen J Torr,Philippe Solano,Inaki Tirados,Johan Esterhuizen,Abdoulaye Diarrassouba,Ernest Salou,Michael J Lehane,Glyn A Vale,Dramane Kaba

doi:10.1371/journal.pntd.0001332

Abstract

BackgroundTsetse flies of the Palpalis group are the main vectors of sleeping sickness in Africa. Insecticide impregnated targets are one of the most effective tools for control. However, the cost of these devices still represents a constraint to their wider use. The objective was therefore to improve the cost effectiveness of currently used devices.Methodology/Principal FindingsExperiments were performed on three tsetse species, namely Glossina palpalis gambiensis and G. tachinoides in Burkina Faso and G. p. palpalis in Côte d'Ivoire. The 1×1 m2 black blue black target commonly used in W. Africa was used as the standard, and effects of changes in target size, shape, and the use of netting instead of black cloth were measured. Regarding overall target shape, we observed that horizontal targets (i.e. wider than they were high) killed 1.6-5x more G. p. gambiensis and G. tachinoides than vertical ones (i.e. higher than they were wide) (P<0.001). For the three tsetse species including G. p. palpalis, catches were highly correlated with the size of the target. However, beyond the size of 0.75 m, there was no increase in catches. Replacing the black cloth of the target by netting was the most cost efficient for all three species.Conclusion/SignificanceReducing the size of the current 1*1 m black-blue-black target to horizontal designs of around 50 cm and replacing black cloth by netting will improve cost effectiveness six-fold for both G. p. gambiensis and G. tachinoides. Studying the visual responses of tsetse to different designs of target has allowed us to design more cost-effective devices for the effective control of sleeping sickness and animal trypanosomiasis in Africa.

Highlights

Tsetse flies (Diptera: Glossinidae) infest about10 million km2 of sub-Saharan Africa where they transmit trypanosomes which cause Human African Trypanosomiasis (HAT; known as sleeping sickness) and African Animal Trypanosomiasis (AAT; known as Nagana)
Conclusion/Significance: Reducing the size of the current 1*1 m black-blue-black target to horizontal designs of around 50 cm and replacing black cloth by netting will improve cost effectiveness six-fold for both G. p. gambiensis and G. tachinoides
Experiments were performed on three tsetse species in Burkina Faso or Cote d’Ivoire

Summary

Introduction

Tsetse flies (Diptera: Glossinidae) infest about million km of sub-Saharan Africa where they transmit trypanosomes which cause Human African Trypanosomiasis (HAT; known as sleeping sickness) and African Animal Trypanosomiasis (AAT; known as Nagana). Tsetse are commonly divided into three, ecologically distinct groups: savannah tsetse ( = Morsitans group) which are largely responsible for transmitting the trypanosomes that cause nagana; riverine tsetse ( = Palpalis group) which play a major role the transmission of Trypanosoma brucei spp., the causative agents of sleeping sickness; and forest tsetse ( = Fusca group) which, generally speaking, do not play an important epidemiological role Tsetse traps or their simplified two-dimensional derivative targets, when impregnated with insecticides, have constituted a central component of tsetse control campaigns in many countries in Africa [3,4,5,6], albeit such baits have been more used against AAT than HAT, except for a few notable exceptions [7,8]. The objective was to improve the cost effectiveness of currently used devices

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Discussion

Conclusion