Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom.
Coordinating Office for Control of Trypanosomiasis in Uganda, Kampala, Uganda.
PLoS Negl Trop Dis. 2022 Jun 29;16(6):e0010222. doi: 10.1371/journal.pntd.0010222. eCollection 2022 Jun.
Tsetse flies (Glossina) transmit Trypanosoma brucei gambiense which causes Gambian human African trypanosomiasis (gHAT) in Central and West Africa. Several countries use Tiny Targets, comprising insecticide-treated panels of material which attract and kill tsetse, as part of their national programmes to eliminate gHAT. We studied how the scale and arrangement of target deployment affected the efficacy of control.
Between 2012 and 2016, Tiny Targets were deployed biannually along the larger rivers of Arua, Maracha, Koboko and Yumbe districts in North West Uganda with the aim of reducing the abundance of tsetse to interrupt transmission. The extent of these deployments increased from 250 km2 in 2012 to ~1600 km2 in 2015. The impact of Tiny Targets on tsetse populations was assessed by analysing catches of tsetse from a network of monitoring traps; sub-samples of captured tsetse were dissected to estimate their age and infection status. In addition, the condition of 780 targets (195/district) was assessed for up to six months after deployment. In each district, mean daily catches of tsetse (G. fuscipes fuscipes) from monitoring traps declined significantly by >80% following the deployment of targets. The reduction was apparent for several kilometres on adjacent lengths of the same river but not in other rivers a kilometre or so away. Expansion of the operational area did not always produce higher levels of suppression or detectable change in the age structure or infection rates of the population, perhaps due to the failure to treat the smaller streams and/or invasion from adjacent untreated areas. The median effective life of a Tiny Target was 61 (41.8-80.2, 95% CI) days.
Scaling-up of tsetse control reduced the population of tsetse by >80% across the intervention area. Even better control might be achievable by tackling invasion of flies from infested areas within and outside the current intervention area. This might involve deploying more targets, especially along smaller rivers, and extending the effective life of Tiny Targets.
采采蝇（舌蝇属）传播布氏冈比亚锥虫，导致中非和西非的冈比亚人类非洲锥虫病（gHAT）。一些国家使用 Tiny Targets，这是一种由经过杀虫剂处理的材料制成的面板，吸引并杀死采采蝇，作为其消除 gHAT 的国家计划的一部分。我们研究了目标部署的规模和安排如何影响控制效果。
2012 年至 2016 年，Tiny Targets 每隔一年在乌干达西北部阿鲁阿、马拉卡、科博科和尤姆贝地区的较大河流沿线部署，目的是减少采采蝇的数量以中断传播。这些部署的范围从 2012 年的250km2 增加到 2015 年的1600km2。通过分析监测陷阱网络中的采采蝇捕获量来评估 Tiny Targets 对采采蝇种群的影响；捕获的采采蝇的亚样本被解剖以估计其年龄和感染状况。此外，在部署后长达六个月的时间内，对 780 个目标（~195/区）的状况进行了评估。在每个地区，监测陷阱中采采蝇（冈比亚舌蝇）的日平均捕获量在目标部署后显著下降了>80%。这种减少在同一条河流的相邻河段上持续了数公里，但在一公里左右的其他河流上则没有。作业区的扩大并不总是产生更高水平的抑制或人口年龄结构或感染率的可检测变化，这可能是由于未能处理较小的溪流和/或来自相邻未处理区域的入侵。Tiny Target 的中位有效寿命为 61（41.8-80.2，95%CI）天。
采采蝇控制的扩大使干预区域内的采采蝇数量减少了>80%。通过解决当前干预区域内外受感染地区的苍蝇入侵问题，可能可以实现更好的控制。这可能涉及部署更多的目标，特别是沿着较小的河流，并延长 Tiny Targets 的有效寿命。
