Chagas Disease Vector Control in a Hyperendemic Setting: The First 11 Years of Intervention in Cochabamba, Bolivia

Background
Chagas disease has historically been hyperendemic in the Bolivian Department of Cochabamba. In the early 2000s, an extensive vector control program was implemented; 1.34 million dwelling inspections were conducted to ascertain infestation (2000–2001/2003–2011), with blanket insecticide spraying in 2003–2005 and subsequent survey-spraying cycles targeting residual infestation foci. Here, we assess the effects of this program on dwelling infestation rates (DIRs).
Methodology/Principal Findings
Program records were used to calculate annual, municipality-level aggregate DIRs (39 municipalities); very high values in 2000–2001 (median: 0.77–0.69) dropped to ∼0.03 from 2004 on. A linear mixed model (with municipality as a random factor) suggested that infestation odds decreased, on average, by ∼28% (95% confidence interval [CI95] 6–44%) with each 10-fold increase in control effort. A second, better-fitting mixed model including year as an ordinal predictor disclosed large DIR reductions in 2001–2003 (odds ratio [OR] 0.11, CI95 0.06–0.19) and 2003–2004 (OR 0.22, CI95 0.14–0.34). Except for a moderate decrease in 2005–2006, no significant changes were detected afterwards. In both models, municipality-level DIRs correlated positively with previous-year DIRs and with the extent of municipal territory originally covered by montane dry forests.
Conclusions/Significance
Insecticide-spraying campaigns had very strong, long-lasting effects on DIRs in Cochabamba. However, post-intervention surveys consistently detected infestation in ∼3% of dwellings, underscoring the need for continuous surveillance; higher DIRs were recorded in the capital city and, more generally, in municipalities dominated by montane dry forest – an eco-region where wild Triatoma infestans are widespread. Traditional strategies combining insecticide spraying and longitudinal surveillance are thus confirmed as very effective means for area-wide Chagas disease vector control; they will be particularly beneficial in highly-endemic settings, but should also be implemented or maintained in other parts of Latin America where domestic infestation by triatomines is still commonplace.

### 背景
恰加斯病（Chagas disease）历史上在玻利维亚科恰班巴省曾呈高度地方流行态势。21世纪初，当地启动了一项大规模媒介控制项目：于2000–2001年及2003–2011年间开展了共计134万户住宅检查，以排查住宅是否被媒介侵袭；2003–2005年实施了全域杀虫剂喷洒，并在后续针对残留侵袭灶开展了调查-喷洒循环工作。本研究旨在评估该项目对住宅侵袭率（dwelling infestation rates, DIRs）的影响。

### 方法/主要结果
研究依托项目档案数据，计算了39个市级行政区的年度聚合住宅侵袭率；2000–2001年的侵袭率处于极高水平（中位数：0.77~0.69），自2004年起降至约0.03。以市级行政区为随机因子的线性混合模型（linear mixed model）显示：随着防控力度每提升10倍，住宅侵袭发生比平均下降约28%（95%置信区间[CI95]：6%~44%）。第二项拟合效果更优的混合模型将年份作为有序预测变量，结果显示2001–2003年与2003–2004年的住宅侵袭率均出现大幅下降（比数比[OR]分别为0.11，95%置信区间0.06~0.19；0.22，95%置信区间0.14~0.34）。除2005–2006年出现小幅下降外，后续未检测到显著变化。两项模型均显示，市级行政区的住宅侵袭率与上一年度的侵袭率及该行政区原生山地干旱森林覆盖面积呈正相关。

### 结论与意义
杀虫剂喷洒项目对科恰班巴省的住宅侵袭率产生了极强且持久的抑制效果。但干预后的调查仍持续在约3%的住宅中检测到侵袭情况，凸显了持续开展监测的必要性；省会城市及以原生山地干旱森林为主的行政区（该生态区内野生骚扰锥蝽[Triatoma infestans]分布广泛）的住宅侵袭率普遍更高。由此可见，结合杀虫剂喷洒与长期监测的传统策略，是区域范围内防控恰加斯病媒介的高效手段；该策略在高度流行地区尤为适用，同时也应在拉丁美洲其他仍普遍存在家栖锥蝽侵袭的地区推广或维持实施。