1. Disease can be a powerful driver of population and community dynamics, as well as evolutionary processes. Disease is also emerging at increasing rates, resulting in massive impacts on populations, communities, and ecosystems. However, assessing these impacts requires foundational knowledge of disease agents and hosts, which is often lacking, particularly in aquatic insects.
2. We describe a recent disease outbreak in caddisflies, suggesting potential consequences for population and community dynamics of the host. We use a series of complementary studies to develop a cohesive foundation of information about this disease, including identification using genomic methods, observational prevalence studies, laboratory experiments to establish transmissibility and fitness consequences, and laboratory and field investigations to infer transmission mechanisms.
3. We identified the infection as being caused by the oomycete Saprolegnia—the first time this parasite has been noted in insect eggs. Prevalence surveys found high prevalence (up to 36%) with variation across space, time, and host species. We demonstrated increasing egg mortality with increasing infection within an egg mass (every 10% increase in infection rate doubles odds of mortality), thereby confirming disease. We established transmissibility and show that transmission occurs through both direct contact with infected egg masses and from background sources, which probably interact to create complex patterns of disease.
4. Taken together, our findings show that conditions necessary for population and community consequences are present. Specifically, increased mortality rates almost certainly occurred during the outbreak, yielding lower larval numbers and potentially altering community interactions. Transmission by contact between egg masses combined with observed species-specific prevalence suggest shifts in the relative performance of different species because of interactions between host and parasite life histories.
5. Outside extreme examples such as chytrid fungus, disease has traditionally received less interest than resource competition or predation in community ecology, although disease ecology is advancing rapidly. One major hurdle is a lack of foundational knowledge characterising disease processes in natural communities, particularly in aquatic insects. Our findings highlight the importance of investigating diseases in insect eggs and provide the foundation for further investigations of how these processes play out at the population and community scale.

中文翻译：

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水生昆虫疾病暴发的特征和后果

1. 疾病可以成为人口和社区动态以及进化过程的强大驱动力。疾病也在以越来越快的速度出现，对人口、社区和生态系统造成巨大影响。然而，评估这些影响需要有关病原体和宿主的基础知识，而这通常是缺乏的，尤其是在水生昆虫中。
2. 我们描述了最近在石蛾中爆发的疾病，表明对宿主种群和社区动态的潜在影响。我们使用一系列补充研究来开发有关这种疾病的信息的连贯性基础，包括使用基因组方法进行识别、观察性流行研究、实验室实验以确定传播性和健康后果，以及实验室和现场调查以推断传播机制。
3. 我们确定这种感染是由卵菌水霉引起的——这是第一次在昆虫卵中发现这种寄生虫。流行率调查发现高流行率（高达 36%）随着空间、时间和宿主物种的变化而变化。我们证明，随着鸡蛋块内感染的增加，鸡蛋死亡率会增加（感染率每增加 10%，死亡率就会增加一倍），从而确认疾病。我们确定了传染性，并表明传播是通过直接接触受感染的卵块和来自背景源的，它们可能相互作用以产生复杂的疾病模式。
4. 综上所述，我们的研究结果表明，存在人口和社区后果所必需的条件。具体来说，几乎可以肯定在爆发期间死亡率增加，导致幼虫数量减少，并可能改变社区互动。通过卵块之间的接触传播以及观察到的物种特异性流行率表明，由于宿主和寄生虫生活史之间的相互作用，不同物种的相对表现发生了变化。
5. 除了壶菌真菌等极端例子外，尽管疾病生态学正在迅速发展，但传统上疾病对社区生态学中的资源竞争或捕食的兴趣要低于资源竞争或捕食。一个主要障碍是缺乏表征自然群落疾病过程的基础知识，尤其是水生昆虫。我们的研究结果强调了调查昆虫卵中疾病的重要性，并为进一步调查这些过程如何在种群和社区规模上发挥作用奠定了基础。