Quantitative evaluation of the strategy to eliminate human African trypanosomiasis in the Democratic Republic of Congo

Rock, Kat S.; Torr, Stephen J.; Lumbala, Crispin; Keeling, Matthew James

doi:10.1186/s13071-015-1131-8

Cited by 96 publications

(189 citation statements)

References 35 publications

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“…The simple and fast nature of this method indicates it could be suitable for the high-throughput processing of tsetse. With prevalence of T. b. gambiense in tsetse from HAT foci predicted to be as low as 1 in 10 5 (17), there is a need for a xenomonitoring tool which can be applied to large numbers of samples. With further optimisation of the assay and DNA extraction protocol, our method could be applied in the remote and low-resource settings typical of most HAT cases.…”

Section: Discussionmentioning

confidence: 99%

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Identification ofTrypanosoma brucei gambienseandT. b. rhodesiensein vectors using multiplexed high-resolution melt analysis

Garrod

Adams

et al. 2020

Preprint

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Section: Discussionmentioning

confidence: 99%

“…This study was also challenged by the unavailability of any field-caught T. b. gambiense infected tsetse flies. As previously mentioned, trypanosome prevalence in HAT foci is predicted to be very low (17), therefore making obtaining sufficient field samples for assay validation an ongoing challenge.…”

Section: Discussionmentioning

confidence: 99%

Identification ofTrypanosoma brucei gambienseandT. b. rhodesiensein vectors using multiplexed high-resolution melt analysis

Garrod

Adams

et al. 2020

Preprint

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“…In addition to tsetse population dynamics described above, adult tsetse in each cell progress through susceptible teneral (juvenile unfed) ( S V ) to either susceptible non-teneral ( G V ), or exposed ( E 1V – E 3V ) and then infectious ( I V ) classes. Instead of having a fixed-time for the tsetse incubation period, or assuming that the incubation period is exponentially distributed, we model three exposed classes as per [14], assuming an Erlang distributed waiting time for the extrinsic incubation period [15]. Hosts in each cell progress through susceptible ( S H ), exposed ( E H ), infected/ infectious ( I H ) and recovered ( R H ) classes.…”

Section: Methodsmentioning

confidence: 99%

Assessing the effect of insecticide-treated cattle on tsetse abundance and trypanosome transmission at the wildlife-livestock interface in Serengeti, Tanzania

Lord

Lea

Allan

et al. 2020

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23In the absence of national control programmes against Rhodesian human African 24 trypanosomiasis, farmer-led treatment of cattle with pyrethroid-based insecticides may be an 25 effective strategy for foci at the edges of wildlife areas, but there is limited evidence to 26 support this. 27 We combined data on insecticide use by farmers, tsetse abundance and trypanosome 28 prevalence with mathematical models to quantify the likely impact of insecticide-treated 29 cattle. 30 Sixteen percent of farmers reported treating cattle with a pyrethroid, and chemical analysis 31 indicated 18% of individual cattle had been treated, in the previous week. Treatment of cattle 32 was estimated to increase daily mortality of tsetse by 5 -14%. Trypanosome prevalence in 33 tsetse, predominantly from wildlife areas, was 1.25% for T. brucei s.l. and 0.03% for T. b. 34 rhodesiense. For 750 cattle sampled from 48 herds, 2.3% were PCR positive for T. brucei s.l. 35 and none for T. b. rhodesiense. Using mathematical models, we estimated there was 8 -29% 36 increase in mortality of tsetse in farming areas and this increase can explain the relatively low 37 prevalence of T. brucei s.l. in cattle. 38Farmer-led treatment of cattle with pyrethroids is likely, in part, to be limiting the spill-over 39 of human-infective trypanosomes from wildlife areas. 40 41 Author summary 42 The acute form of sleeping sickness in Africa is caused by the parasite Trypanosoma brucei 43 rhodesiense. It is transmitted by tsetse flies and can be maintained in cycles involving both 44 livestock and wildlife as hosts. Humans are incidentally infected and are particularly at risk 3 45 of infection near protected areas where there are both wildlife and suitable habitat for tsetse. 46In these regions, the tsetse vector cannot be eradicated, nor can infection be prevented in 47 wildlife. Here we use field studies of tsetse and livestock in combination with mathematical 48 models of tsetse population change and trypanosome transmission to show that use of 49 pyrethroid-based insecticides on cattle by farmers at the edge of protected areas could be 50 contributing to lowering the risk of sleeping sickness in Serengeti District, Tanzania. To our 51 knowledge, our study is the first to report farmer-led tsetse control, co-incident with tsetse 52 decline and relatively low prevalence of T. brucei s.l. in cattle. 53 54 Introduction 55 In East and Southern Africa, tsetse flies (Glossina spp) transmit Trypanosoma brucei 56 rhodesiense, which causes Rhodesian human African trypanosomiasis (r-HAT). Tsetse also 57 transmit T. congolense, T. vivax and T. brucei, the causative agents of animal African 58 trypanosomiasis (AAT) in livestock. 59 Trypanosoma brucei s.l., T. congolense and T. vivax can circulate in transmission cycles 60 involving livestock or wild mammals [1]. The extensive conservation areas of East and 61 Southern Africa that support tsetse, as well as wildlife, can therefore be foci for r-HAT and 62 AAT. At the interface of wildlife-and livestock areas, ...

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“…Behavioural studies have shown that this species is responsive to Tiny Targets [13]. Accordingly, we implemented a large-scale trial of Tiny Targets in Yasa Bonga Health Zone, one of the foci where the addition of vector control to screening activities is predicted to accelerate progress towards the elimination goal [4,6]. To assist in the design and monitoring of the tsetse control operation, we also conducted a large-scale entomological survey of G. f. quanzensis in Yasa Bonga and its neighbouring health zones of Masi Manimba and Mosango ( Figure 1) and used remotely-sensed data to produce a map of tsetse habitat suitability for this important vector, which guided the deployment of targets and allowed us to assess their impact.…”

Section: Introductionmentioning

confidence: 99%

Impact of Tiny Targets onGlossina fuscipes quanzensis, the primary vector of Human African Trypanosomiasis in the Democratic Republic of the Congo

Tirados

Hope

Selby

et al. 2020

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BackgroundOver the past 20 years there has been a >95% reduction in the number of Gambian Human African trypanosomiasis (g-HAT) cases reported globally, largely as a result of large-scale active screening and treatment programmes. There are however still foci where the disease persists, particularly in parts of the Democratic Republic of the Congo (DRC). Additional control efforts such as tsetse control using Tiny Targets may therefore be required to achieve g-HAT elimination goals. The purpose of this study was to evaluate the impact of Tiny Targets within DRC. Methodology/Principal findingsIn 2015-2017, pre-and post-intervention tsetse abundance data were collected from 1,234 unique locations across three neighbouring Health Zones (Yasa Bonga, Mosango, Masi Manimba). Remotely sensed dry season data were combined with pre-intervention tsetse presence/absence data from 332 locations within a species distribution modelling framework to produce a habitat suitability map. The impact of Tiny Targets on the tsetse population was then evaluated by fitting a generalised linear mixed model to the relative fly abundance data collected from 889 post-intervention monitoring sites within Yasa Bonga, with habitat suitability, proximity to the intervention and intervention duration as covariates. Immediately following the introduction of the intervention, we observe a dramatic reduction in fly catches by > 85% (pre-intervention: 0.78 flies/trap/day, 95% CI 0.676-0.900; 3 month post-intervention: 0.11 flies/trap/day, 95% CI 0.070-0.153) which is sustained throughout the study period. Declines in catches were negatively associated with proximity to Tiny Targets, and while habitat suitability is positively associated with abundance its influence is reduced in the presence of the intervention. Conclusions/SignificanceThis study adds to the body of evidence demonstrating the impact of Tiny Targets on tsetse across a range of ecological settings, and further characterises the factors which modify its impact. The habitat suitability maps have the potential to guide the expansion of tsetse control activities in this area. Authors SummaryThere have been large declines in the number of cases of sleeping sickness as a result of programmes that actively screen and treat the at-risk population. Additional control is needed in areas where the disease persists such as parts of the Democratic Republic of Congo (DRC). The disease is transmitted by tsetse flies, and reducing the tsetse population using Tiny Targets has been shown to control the disease in other countries. Extensive tsetse monitoring has been undertaken in one Health Zone in DRC where Tiny Targets have been deployed. We used these data to gain a better understanding of tsetse habitat, to produce habitat suitability maps, and to subsequently measure the impact of Tiny Targets on the tsetse population. We show that tsetse flies are largely found along rivers and surrounding densely vegetated habitat, with there being a positive relationship between habitat suitability and the numb...

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Quantitative evaluation of the strategy to eliminate human African trypanosomiasis in the Democratic Republic of Congo

Cited by 96 publications

References 35 publications

Identification ofTrypanosoma brucei gambienseandT. b. rhodesiensein vectors using multiplexed high-resolution melt analysis

Identification ofTrypanosoma brucei gambienseandT. b. rhodesiensein vectors using multiplexed high-resolution melt analysis

Assessing the effect of insecticide-treated cattle on tsetse abundance and trypanosome transmission at the wildlife-livestock interface in Serengeti, Tanzania

Impact of Tiny Targets onGlossina fuscipes quanzensis, the primary vector of Human African Trypanosomiasis in the Democratic Republic of the Congo

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