MRC Centre for Environment & Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, United Kingdom.
Institute of Advanced Studies, University of São Paulo, São Paulo, Brazil.
PLoS Negl Trop Dis. 2024 Sep 12;18(9):e0012397. doi: 10.1371/journal.pntd.0012397. eCollection 2024 Sep.
Seasonal fluctuations in weather are recognized as factors that affect both Aedes (Ae.) aegypti mosquitoes and the diseases they carry, such as dengue fever. The El Niño-Southern Oscillation (ENSO) is widely regarded as one of the most impactful atmospheric phenomena on Earth, characterized by the interplay of shifting ocean temperatures, trade wind intensity, and atmospheric pressure, resulting in extensive alterations in climate conditions. In this study, we investigate the influence of ENSO and local weather conditions on the spatio-temporal variability of Ae. aegypti infestation index.
We collected seasonal entomological survey data of immature forms of Ae. aegypti mosquitoes (Breteau index), as well as data on temperature, rainfall and the Oceanic Niño Index (ONI) for the period 2008-2018 over the 645 municipalities of the subtropical State of São Paulo (Brazil). We grounded our analytical approach on a Bayesian framework and we used a hierarchical spatio-temporal model to study the relationship between ENSO tracked by ONI, seasonal weather fluctuations and the larval index, while adjusting for population density and wealth inequalities.
Our results showed a relevant positive effect for El Niño on the Ae. aegypti larval index. In particular, we found that the number of positive containers would be expected to increase by 1.30-unit (95% Credible Intervals (CI): 1.23 to 1.37) with El Niño events (i.e., ≥ 1°C, moderate to strong) respect to neutral (and weak) events. We also found that seasonal rainfall exceeding 153.12 mm appears to have a notable impact on vector index, leading potentially to the accumulation of ample water in outdoor discarded receptacles, supporting the aquatic phase of mosquito development. Additionally, seasonal temperature above 23.30°C was found positively associated to the larval index. Although the State of São Paulo as a whole has characteristics favourable to proliferation of the vector, there were specific areas with a greater tendency for mosquito infestation, since the most vulnerable areas are predominantly situated in the central and northern regions of the state, with hot spots of abundance in the south, especially during El Niño events. Our findings also indicate that social disparities present in the municipalities contributes to Ae. aegypti proliferation.
Considering the anticipated rise in both the frequency and intensity of El Niño events in the forthcoming decades as a consequence of climate change, the urgency to enhance our ability to track and diminish arbovirus outbreaks is crucial.
天气的季节性波动被认为是影响埃及伊蚊（Aedes aegypti）和携带疾病的因素之一，例如登革热。厄尔尼诺-南方涛动（ENSO）被广泛认为是地球上最具影响力的大气现象之一，其特征是海洋温度、信风强度和气压的相互作用，导致气候条件的广泛变化。在这项研究中，我们调查了 ENSO 和当地天气条件对埃及伊蚊滋生指数的时空变化的影响。
我们收集了 2008 年至 2018 年期间亚热带圣保罗州（巴西）645 个市镇的埃及伊蚊幼虫形式的季节性昆虫学调查数据（布雷特指数），以及温度、降雨量和海洋尼诺指数（ONI）数据。我们的分析方法基于贝叶斯框架，使用分层时空模型来研究 ONI 跟踪的 ENSO、季节性天气波动和幼虫指数之间的关系，同时调整人口密度和贫富差距。
我们的结果表明，厄尔尼诺现象对埃及伊蚊幼虫指数有显著的正效应。具体来说，我们发现，与中性（和弱）事件相比，厄尔尼诺事件（即≥1°C，中等至强）预计会使阳性容器的数量增加 1.30 个单位（95%可信区间（CI）：1.23 至 1.37）。我们还发现，季节性降雨量超过 153.12 毫米似乎对矢量指数有显著影响，导致户外丢弃容器中积累了大量水，支持蚊子发育的水生阶段。此外，季节性温度高于 23.30°C 与幼虫指数呈正相关。尽管整个圣保罗州具有有利于媒介繁殖的特征，但也有一些地区更倾向于蚊子滋生，因为最脆弱的地区主要位于该州的中部和北部，南部地区尤其在厄尔尼诺事件期间是滋生的热点。我们的研究结果还表明，城市之间存在的社会差异有助于埃及伊蚊的滋生。
考虑到未来几十年由于气候变化，厄尔尼诺事件的频率和强度预计会增加，加强我们跟踪和减少虫媒病毒爆发的能力是至关重要的。
