Improving the Cost-Effectiveness of Visual Devices for the Control of Riverine Tsetse Flies, the Major Vectors of Human African Trypanosomiasis

Esterhuizen, Johan; Rayaissé, Jean Baptiste; Tirados, Iñaki; Mpiana, Serge; Solano, Philippe; Vale, G. A.; Lehane, Michael J.; Torr, Stephen J.

doi:10.1371/journal.pntd.0001257

Cited by 63 publications

(81 citation statements)

References 22 publications

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“…Where only riverine tsetse are present, odour baits are not required and much smaller 0.5 x 0.25 m 'tiny targets' can be highly effective (Esterhuizen et al, 2011). These can be transported by bicycle or motorcycle, leading to much lower logistics costs than those for installing and servicing conventional targets.…”

Section: Stationary Baits -Targets and Trapsmentioning

confidence: 99%

Mapping the benefit-cost ratios of interventions against bovine trypanosomosis in Eastern Africa

Shaw

Wint

Cecchi³

et al. 2015

Preventive Veterinary Medicine

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This study builds upon earlier work mapping the potential benefits from bovine trypanosomosis control and analysing the costs of different approaches. Updated costs were derived for five intervention techniques: trypanocides, targets, insecticide-treated cattle, aerial spraying and the release of sterile males. Two strategies were considered: continuous control and elimination. For mapping the costs, cattle densities, environmental constraints, and the presence of savannah or riverine tsetse species were taken into account. These were combined with maps of potential benefits to produce maps of benefit-cost ratios. The results illustrate a diverse picture, and they clearly indicate that no single technique or strategy is universally profitable. For control using trypanocide prophylaxis, returns are modest, even without accounting for the risk of drug resistance but, in areas of low cattle densities, this is the only approach that yields a positive return. Where cattle densities are sufficient to support it, the use of insecticidetreated cattle stands out as the most consistently profitable technique, widely achieving benefit-cost ratios above 5. In parts of the high-potential areas such as the mixed farming, high-oxen-use zones of western Ethiopia, the fertile crescent north of Lake Victoria and the dairy production areas in western and central Kenya, all tsetse control strategies achieve benefit-cost ratios from 2 to over 15, and for elimination strategies, ratios from 5 to over 20. By contrast, in some areas, notably where cattle densities are below 20 per km 2 , the costs of interventions against tsetse match or even outweigh the benefits, especially for control scenarios using aerial spraying or the deployment of targets where both savannah and riverine flies are present. If the burden of human African trypanosomosis were factored in, the benefit-cost ratios of some of the low-return areas would be considerably increased. Comparatively, elimination strategies give rise to higher benefit-cost ratios than do those for continuous control. However, the costs calculated for elimination assume problem-free, large scale operations, and they rest on the outputs of entomological models that are difficult to validate in the field. Experience indicates that the conditions underlying successful and sustained elimination campaigns are seldom met. By choosing the most appropriate thresholds for benefit-cost ratios, decision-makers and planners can use the maps to define strategies, assist in prioritising areas for intervention, and help choose among intervention techniques and approaches. The methodology would have wider applicability in analysing other disease constraints with a strong spatial component.

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Section: Stationary Baits -Targets and Trapsmentioning

confidence: 99%

Mapping the benefit-cost ratios of interventions against bovine trypanosomosis in Eastern Africa

Shaw

Wint

Cecchi³

et al. 2015

Preventive Veterinary Medicine

View full text Add to dashboard Cite

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“…Therefore, concerted efforts have been underway to improve the cost and efficiency of control devices for riverine tsetse so that they might contribute to efforts to eliminate Gambian HAT (e.g. [10,11,12,13,14,15,16]).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, although larger targets are most attractive to both riverine and savannah tsetse, the former are relatively more attracted to smaller visual targets than the latter [7,12]. These behavioural differences are probably not the result of differences in tsetse physiology.…”

Section: Introductionmentioning

confidence: 99%

“…Instead, narrow and densely vegetated riverine habitats mean that odour plumes are of limited utility in host seeking, and the reduced probability of encountering hosts in such habitats necessitates less selectivity when one is encountered [7,17]. Identification of these crucial behavioural differences has allowed the development of ‘tiny targets’ for riverine tsetse, which comprise a 0.25 m x 0.25 m blue polyester panel adjacent to a 0.25 m x 0.25 m black polyethylene mosquito net panel, with both panels impregnated with deltamethrin insecticide [5,10,12,14]. The blue fabric panel serves to attract tsetse, whilst the mosquito net panel is thought to intercept circling flies, overcoming their reduced tendency to alight directly on small visual targets [12].…”

Section: Introductionmentioning

confidence: 99%

“…Identification of these crucial behavioural differences has allowed the development of ‘tiny targets’ for riverine tsetse, which comprise a 0.25 m x 0.25 m blue polyester panel adjacent to a 0.25 m x 0.25 m black polyethylene mosquito net panel, with both panels impregnated with deltamethrin insecticide [5,10,12,14]. The blue fabric panel serves to attract tsetse, whilst the mosquito net panel is thought to intercept circling flies, overcoming their reduced tendency to alight directly on small visual targets [12]. Versus the large devices used for savannah tsetse, tiny targets offer considerable savings in costs associated with materials, transport, and deployment, but with only a small penalty in terms of reduced attractiveness to tsetse [10,12].…”

Section: Introductionmentioning

confidence: 99%

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Developing photoreceptor-based models of visual attraction in riverine tsetse, for use in the engineering of more-attractive polyester fabrics for control devices

Santer

2017

PLoS Negl Trop Dis

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Riverine tsetse transmit the parasites that cause the most prevalent form of human African trypanosomiasis, Gambian HAT. In response to the imperative for cheap and efficient tsetse control, insecticide-treated ‘tiny targets’ have been developed through refinement of tsetse attractants based on blue fabric panels. However, modern blue polyesters used for this purpose attract many less tsetse than traditional phthalogen blue cottons. Therefore, colour engineering polyesters for improved attractiveness has great potential for tiny target development. Because flies have markedly different photoreceptor spectral sensitivities from humans, and the responses of these photoreceptors provide the inputs to their visually guided behaviours, it is essential that polyester colour engineering be guided by fly photoreceptor-based explanations of tsetse attraction. To this end, tsetse attraction to differently coloured fabrics was recently modelled using the calculated excitations elicited in a generic set of fly photoreceptors as predictors. However, electrophysiological data from tsetse indicate the potential for modified spectral sensitivities versus the generic pattern, and processing of fly photoreceptor responses within segregated achromatic and chromatic channels has long been hypothesised. Thus, I constructed photoreceptor-based models explaining the attraction of G. f. fuscipes to differently coloured tiny targets recorded in a previously published investigation, under differing assumptions about tsetse spectral sensitivities and organisation of visual processing. Models separating photoreceptor responses into achromatic and chromatic channels explained attraction better than earlier models combining weighted photoreceptor responses in a single mechanism, regardless of the spectral sensitivities assumed. However, common principles for fabric colour engineering were evident across the complete set of models examined, and were consistent with earlier work. Tools for the calculation of fly photoreceptor excitations are available with this paper, and the ways in which these and photoreceptor-based models of attraction can provide colorimetric values for the engineering of more-attractively coloured polyester fabrics are discussed.

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Effects of vector control on the population structure of tsetse ( Glossina fuscipes fuscipes ) in western Kenya

et al. 2018

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Displacement rates of tsetse affect performance of targets during vector control. Fly size, one of the indicators of population structure usually obtained from wing measurement, is among the determinants of displacement rates. Although recovery of tsetse in previous intervention areas has been widely reported, the population structure of tsetse that recover is rarely evaluated despite being associated with displacements rates. Previously, intervention trials had reduced tsetse densities by over 90% from >3 flies/trap/day to <1fly/trap/day on Big Chamaunga and Manga islands of Lake Victoria in western Kenya. In this study, we assessed the recovery in densities of Glossina fuscipes fuscipes on the two islands and evaluated the effects vector control might have on the population structure. A before and after intervention study was undertaken on four islands of Lake Victoria in western Kenya; Small and Big Chamaunga, Manga and Rusinga Islands, two of which tsetse control intervention had previously been undertaken. Three years after intervention average G. f. fuscipes catches in biconical traps were estimated on each island. Wing centroid size (CS) (a measurement of fly size) and shape, indicators of the population structure of flies from the four islands were compared using geometric morphometric analyses. CS and shape of available female but not male tsetse wings obtained before the intervention trial on Big and Small Chamaunga islands were compared with those from the same islands after the intervention trial. G. f. fuscipes apparent density on the previous intervention islands were>9 flies/trap/day. Irrespective of sex, wing shape did not isolate tsetse based on their islands of origin. The fly size from Big and Small Chamaunga did not differ significantly before intervention trials (P = 0.728). However, three years after the intervention flies from Big Chamaunga were significantly smaller than those from Small Chamaunga (P < 0.003). Further, there was an increase in the divergence of wing morphology between flies collected from Big Chamaunga and those from Small Chamaunga after tsetse control. In conclusion, even though populations are not isolated, vector control could influence the population structure of tsetse by exerting size and wing morphology differential selection pressures. Therefore, we recommend further studies to understand the mechanism behind this as it may guide future vector control strategies.

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Improving the Cost-Effectiveness of Visual Devices for the Control of Riverine Tsetse Flies, the Major Vectors of Human African Trypanosomiasis

Cited by 63 publications

References 22 publications

Mapping the benefit-cost ratios of interventions against bovine trypanosomosis in Eastern Africa

Mapping the benefit-cost ratios of interventions against bovine trypanosomosis in Eastern Africa

Developing photoreceptor-based models of visual attraction in riverine tsetse, for use in the engineering of more-attractive polyester fabrics for control devices

Effects of vector control on the population structure of tsetse ( Glossina fuscipes fuscipes ) in western Kenya

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