Lenhart Audrey, Orelus Nicolas, Maskill Rachael, Alexander Neal, Streit Thomas, McCall P J
Vector Group, Liverpool School of Tropical Medicine, Liverpool, UK.
Trop Med Int Health. 2008 Jan;13(1):56-67. doi: 10.1111/j.1365-3156.2007.01966.x.
Insecticide-treated bednets (ITNs) are effective in preventing nocturnally transmitted vector-borne diseases, but their effect on diurnally active dengue vectors has never been studied. We investigated the efficacy of ITNs in reducing Aedes aegypti populations and dengue transmission.
A cluster-randomized trial was carried out in Leogane, Haiti between July 2003 and July 2004. The study area (1017 houses) was divided into 18 sectors (clusters): nine received ITNs (Olyset(R) long-lasting insecticidal bednets) and nine were untreated controls. Entomological surveys [measuring Breteau (BI), house (HI), container (CI) and pupae per person (PPI) indices and oviposition activity] were undertaken at baseline and at 1 and 5 months post-intervention. All houses were georeferenced to enable spatial analysis. Control sectors received ITNs at 6 months, and a final entomological and attitudinal survey was undertaken at 12 months after baseline. Anti-dengue IgM seropositivity rates were measured at baseline and after 12 months. Efficacy of ITNs was assessed by WHO cone bioassays.
At 1-month post-intervention, entomological indices fell in all sectors, with HI and BI in the bednet sectors reduced by 6.7 (95% CI -10.6, -2.7; P < 0.01) and 8.4 (95% CI -14.1, -2.6; P < 0.01) respectively. Moreover at 1 month, ovitraps in control sectors were significantly more likely to be positive than in bednet sectors (P < 0.01). By 5 months, all indices remained low and HI, CI and BI were also significantly lower than that of baseline in the control arm. Curiously, at 5 months, HI, CI and BI were lower in the control arm than that in the bednet arm. A final survey, 12 months after the initial baseline study (5 months after bednets had been given to all households) indicated that all indices were significantly lower than that at baseline (P < 0.001). Control houses located within 50 m of a bednet house had significantly lower CI (Z = -2.67, P = 0.008) and PPI (Z = -2.19, P = 0.028) at 1 month, an effect that extended to 100 m by 5 months (Z = -2.03, P = 0.042 and Z = -2.37, P = 0.018 respectively), suggesting a spill-over effect of the bednets. An IgM serosurvey showed a 15.3% decrease (95% CI 5.0-25.5%, P < 0.01) in the number of IgM-positive individuals from baseline to12 months later.
Insecticide-treated bednets had an immediate effect on dengue vector populations after their introduction, and over the next 5-12 months, the presence of ITNs may have continued to affect vector populations and dengue transmission.
经杀虫剂处理的蚊帐（ITNs）在预防夜间传播的病媒传播疾病方面有效，但它们对日间活动的登革热媒介的影响从未被研究过。我们调查了经杀虫剂处理的蚊帐在减少埃及伊蚊种群和登革热传播方面的效果。
2003年7月至2004年7月在海地的莱奥甘进行了一项整群随机试验。研究区域（1017所房屋）被分为18个区（群组）：9个区接受经杀虫剂处理的蚊帐（Olyset®长效杀虫蚊帐），9个区为未处理的对照区。在基线以及干预后1个月和5个月进行了昆虫学调查[测量布雷托指数（BI）、房屋指数（HI）、容器指数（CI）和每人蛹指数（PPI）以及产卵活动]。所有房屋都进行了地理定位以便进行空间分析。对照区在6个月时接受经杀虫剂处理的蚊帐，并在基线后12个月进行了最终的昆虫学和态度调查。在基线和12个月后测量了抗登革热IgM血清阳性率。经杀虫剂处理的蚊帐的效果通过世卫组织锥形生物测定法进行评估。
干预后1个月，所有区的昆虫学指数均下降，蚊帐区的HI和BI分别降低了6.7（95%可信区间 -10.6，-2.7；P<0.01）和8.4（95%可信区间 -14.1，-2.6；P<0.01）。此外，在1个月时，对照区的诱蚊产卵器阳性的可能性显著高于蚊帐区（P<0.01）。到5个月时，所有指数仍保持在低水平，对照区的HI、CI和BI也显著低于基线水平。奇怪的是，在5个月时，对照区的HI、CI和BI低于蚊帐区。在初始基线研究12个月后（给所有家庭发放蚊帐5个月后）的最终调查表明，所有指数均显著低于基线水平（P<0.001）。在1个月时，位于距有蚊帐房屋50米内区域的对照房屋的CI（Z = -2.67，P = 0.008）和PPI（Z = -2.19，P = 0.028）显著更低，到5个月时这种影响扩展到了100米（分别为Z = -2.03，P = 0.042和Z = -2.37，P = 0.018），这表明蚊帐有溢出效应。一项IgM血清学调查显示，从基线到12个月后，IgM阳性个体数量减少了15.3%（95%可信区间5.0 - 25.5%，P<0.01）。
经杀虫剂处理的蚊帐在引入后对登革热媒介种群有立即影响，并且在接下来的5至12个月里，经杀虫剂处理的蚊帐的存在可能持续影响媒介种群和登革热传播。
