Evaluation of Spatially Targeted Strategies to Control Non-Domiciliated Triatoma dimidiata Vector of Chagas Disease

BackgroundChagas disease is a major neglected tropical disease with deep socio-economical effects throughout Central and South America. Vector control programs have consistently reduced domestic populations of triatomine vectors, but non-domiciliated vectors still have to be controlled efficiently. Designing control strategies targeting these vectors is challenging, as it requires a quantitative description of the spatio-temporal dynamics of village infestation, which can only be gained from combinations of extensive field studies and spatial population dynamic modelling.Methodology/Principal FindingsA spatially explicit population dynamic model was combined with a two-year field study of T. dimidiata infestation dynamics in the village of Teya, Mexico. The parameterized model fitted and predicted accurately both intra-annual variation and the spatial gradient in vector abundance. Five different control strategies were then applied in concentric rings to mimic spatial design targeting the periphery of the village, where vectors were most abundant. Indoor insecticide spraying and insect screens reduced vector abundance by up to 80% (when applied to the whole village), and half of this effect was obtained when control was applied only to the 33% of households closest to the village periphery. Peri-domicile cleaning was able to eliminate up to 60% of the vectors, but at the periphery of the village it has a low effect, as it is ineffective against sylvatic insects. The use of lethal traps and the management of house attractiveness provided similar levels of control. However this required either house attractiveness to be null, or ≥5 lethal traps, at least as attractive as houses, to be installed in each household.Conclusion/SignificanceInsecticide and insect screens used in houses at the periphery of the village can contribute to reduce house infestation in more central untreated zones. However, this beneficial effect remains insufficient to allow for a unique spatially targeted strategy to offer protection to all households. Most efficiently, control should combine the use of insect screens in outer zones to reduce infestation by both sylvatic and peri-domiciliated vectors, and cleaning of peri-domicile in the centre of the village where sylvatic vectors are absent. The design of such spatially mixed strategies of control offers a promising avenue to reduce the economic cost associated with the control of non-domiciliated vectors.

背景
恰加斯病（Chagas disease）是一种严重的被忽视热带病，在中美洲和南美洲造成了深远的社会经济影响。媒介防控项目长期以来持续减少家栖型锥蝽媒介的种群数量，但野栖型锥蝽媒介（non-domiciliated vectors）仍需得到高效防控。针对这类媒介设计防控策略颇具挑战，因为需要对村庄的媒介侵染时空动态进行定量描述，而这类数据仅能通过大规模野外研究与空间种群动态模型相结合的方式获取。

方法/主要结果
本研究将空间显式种群动态模型与针对墨西哥特亚村（Teya）骚扰锥蝽（T. dimidiata）侵染动态的两年野外研究相结合。经过参数化的模型能够精准拟合并预测媒介丰度的年内变化与空间梯度分布。随后，针对媒介丰度最高的村庄外围区域，以同心圆布局应用了五种不同的防控策略，以模拟空间靶向防控方案。室内杀虫剂喷洒与防虫网布设可使媒介丰度最高降低80%（当在全村范围内实施时）；若仅对距离村庄外围最近的33%住户实施防控，则可获得该效果的一半水平。居所周边清洁可消灭最高达60%的媒介，但在村庄外围区域效果有限，因为该方法对野栖昆虫无效。使用致死诱捕器与调节居所诱虫性的防控策略可达到相近的防控效果，但该策略需满足以下任一条件：居所诱虫性完全归零，或在每户住宅中安装至少5个与住宅诱虫性相当的致死诱捕器。

结论/意义
在村庄外围住户家中使用杀虫剂与防虫网，可助力降低更为核心的未防控区域的住宅侵染率。但该有益效果仍不足以支撑仅依靠单一空间靶向策略为所有住户提供防护。最为高效的防控方案应结合以下措施：在村庄外围区域布设防虫网，以降低野栖型与居所周边型媒介的侵染；在无野栖媒介分布的村庄核心区域开展居所周边清洁工作。这类空间混合防控策略的设计，为降低与防控野栖型锥蝽媒介相关的经济成本提供了极具前景的路径。