Núcleo de Medicina Tropical, Faculdade de Medicina, Universidade de Brasília, Brasilia, Brazil.
Secretaria de Vigilância em Saúde, Ministério da Saúde, Brasilia, Brazil.
Parasit Vectors. 2020 Jul 14;13(1):352. doi: 10.1186/s13071-020-04221-z.
Aedes aegypti and Culex quinquefasciatus are the main urban vectors of arthropod-borne viruses causing human disease, including dengue, Zika, or West Nile. Although key to disease prevention, urban-mosquito control has met only limited success. Alternative vector-control tactics are therefore being developed and tested, often using entomological endpoints to measure impact. Here, we test one promising alternative and assess how three such endpoints perform at measuring its effects.
We conducted a 16-month, two-arm, cluster-randomized controlled trial (CRCT) of mosquito-disseminated pyriproxyfen (MD-PPF) in central-western Brazil. We used three entomological endpoints: adult-mosquito density as directly measured by active aspiration of adult mosquitoes, and egg-trap-based indices of female Aedes presence (proportion of positive egg-traps) and possibly abundance (number of eggs per egg-trap). Using generalized linear mixed models, we estimated MD-PPF effects on these endpoints while accounting for the non-independence of repeated observations and for intervention-unrelated sources of spatial-temporal variation.
On average, MD-PPF reduced adult-mosquito density by 66.3% (95% confidence interval, 95% CI: 47.3-78.4%); Cx. quinquefasciatus density fell by 55.5% (95% CI: 21.1-74.8%), and Ae. aegypti density by 60.0% (95% CI: 28.7-77.5%). In contrast, MD-PPF had no measurable effect on either Aedes egg counts or egg-trap positivity, both of which decreased somewhat in the intervention cluster but also in the control cluster. Egg-trap data, therefore, failed to reflect the 60.0% mean reduction of adult Aedes density associated with MD-PPF deployment.
Our results suggest that the widely used egg-trap-based monitoring may poorly measure the impact of Aedes control; even if more costly, direct monitoring of the adult mosquito population is likely to provide a much more realistic and informative picture of intervention effects. In our CRCT, MD-PPF reduced adult-mosquito density by 66.3% in a medium-sized, spatially non-isolated, tropical urban neighborhood. Broader-scale trials will be necessary to measure MD-PPF impact on arboviral-disease transmission.
埃及伊蚊和致倦库蚊是引起人类疾病的虫媒病毒的主要城市传播媒介，包括登革热、寨卡病毒或西尼罗河病毒。尽管城市蚊虫控制是预防疾病的关键，但仅取得了有限的成功。因此，正在开发和测试替代的蚊虫控制策略，通常使用昆虫学终点来衡量其影响。在这里，我们测试了一种有前途的替代方法，并评估了这三个终点在衡量其效果方面的表现。
我们在巴西中西部进行了一项为期 16 个月的、两臂、集群随机对照试验（CRCT），对蚊虫传播的吡丙醚（MD-PPF）进行了测试。我们使用了三个昆虫学终点：通过主动抽吸成年蚊子直接测量的成年蚊子密度，以及基于卵阱的雌性埃及伊蚊存在（阳性卵阱的比例）和可能丰度（每个卵阱的卵数）的指数。使用广义线性混合模型，我们在考虑到重复观测的非独立性和与干预无关的时空变化来源的情况下，估计了 MD-PPF 对这些终点的影响。
平均而言，MD-PPF 使成年蚊子密度降低了 66.3%（95%置信区间，95%CI：47.3-78.4%）；致倦库蚊密度下降了 55.5%（95%CI：21.1-74.8%），埃及伊蚊密度下降了 60.0%（95%CI：28.7-77.5%）。相比之下，MD-PPF 对埃及伊蚊卵计数或卵阱阳性率没有可衡量的影响，这两个指标在干预组和对照组都略有下降。因此，卵阱数据未能反映与 MD-PPF 部署相关的成年埃及伊蚊密度平均 60.0%的降低。
我们的结果表明，广泛使用的基于卵阱的监测可能无法很好地衡量埃及伊蚊控制的效果；即使成本更高，直接监测成年蚊子种群可能会提供更真实和更具信息性的干预效果。在我们的 CRCT 中，MD-PPF 使中型、空间非隔离的热带城市社区中的成年蚊子密度降低了 66.3%。需要更广泛的试验来衡量 MD-PPF 对虫媒病毒传播的影响。
