Collaborative Research: Disease Dynamics in Degraded Nurseries: A Viral Disease in Spiny Lobster

新出现的传染病问题在海洋生态系统中尤其严重，海洋生态系统的研究落后于陆地生态系统。关于海洋生物新出现疾病的报告在世界范围内不断增加，特别是在沿海环境中，有令人信服的证据表明，这些事件与水质和生境完整性的退化有关。然而，这些研究中很少产生能够将当地环境变化与疾病动态结合起来的流行病学模型，而且没有一个涉及活动的海洋动物。最近发现了一种致命的致病性病毒，感染了佛罗里达群岛的加勒比小龙虾（Panulirus argus），这是报道的第一种龙虾病毒。该病主要通过接触传播，传染性与个体发生有关；幼年龙虾易受感染，成年龙虾则不然。这种疾病的一个显著特点是，它不仅会杀死受感染的个体，还会改变健康个体的行为，这些健康个体通常是社交的，但会积极避免与患病的同类接触。这种疾病出现的根本原因仍然是一个谜，但在它出现之前，人类引起的苗圃栖息地的变化和佛罗里达州南部水质的下降。一种假设是，水质的恶化，包括大沼泽地恢复预计会出现的水质恶化，是一种微妙的压力源，损害了龙虾对感染的抵抗力，促进了疾病的传播。同时，水质差改变了苗圃生境结构，从而通过增加宿主接触率间接影响疾病动态，从而增加疾病传播。可能抵消这些环境变化影响的是宿主行为的个体发生变化、对感染的易感性以及对可能限制疾病传播的患病个体的回避。该项目将包括一个雄心勃勃的实验室、实地和建模研究计划，其目标是对栖息地完整性减少在退化的沿海海洋生态系统中病毒性疾病在社会动物中传播所起的多方面作用建立预测性理解。该项目以美国国家科学基金会先前的赞助为基础，汇集了在龙虾生物学、生态建模、无脊椎动物病理学和分子生物学方面具有丰富经验的多学科科学家的才能。虽然目前的研究重点是佛罗里达刺龙虾中新出现的PaV1病毒作为模型系统，但本项目的结果将有助于更好地了解栖息地结构、宿主抗性的个体发生变化和宿主行为在调节自然种群中受人为侵害的疾病传播中的作用。该项目的目标是：(1)通过将宿主行为、疾病易感性和疾病传播的个体发生方面纳入现有的空间显性、基于个体的龙虾种群模型，探索控制疾病传播的潜在机制，并预测与苗期栖息地结构和水质压力因素变化相关的病毒流行。(2)在中观和田间实验中定量检验苗圃生境结构改变对寄主运动、寄主空间分布和病毒传播等个体发生差异的影响。(3)在实验室实验中确定潜在的环境压力因素，如极端温度和盐度，或水质差是否会改变宿主对病毒感染或感染性的易感性。(4)在实验室研究中表征宿主疾病状态，并利用分子和组织学技术确定其在自然界中的流行程度。更广泛的影响：该项目将包括本科生、研究生和博士后的持续参与和交叉培训，包括本科生参与VIMS和ODU的NSF REU项目。与当地资源管理机构的联系确保了该项目的基础科学成果将在管理决策中得到应用。这些私人机构将在基韦斯特共同主办一次为期一天的研讨会，与会者包括渔民、科学家、环境管理人员和感兴趣的公众，会上将讨论佛罗里达群岛最近的科学发现和环境问题。继续进行的分子工作将产生新的检测病毒感染组织的方法，这可能有助于官员监测受感染龙虾在世界各地的潜在传播和运输。此外，建模组件将帮助管理人员预测疾病在野生种群中的传播。

The problem of emerging infectious diseases is particularly acute in marine ecosystems where studies lag behind those in terrestrial systems. Reports of emerging diseases in marine organisms are increasing worldwide, particularly in coastal environments, where the evidence is compelling that these events are associated with the degradation of water quality and habitat integrity. Yet, few of these studies have produced epidemiological models capable of integrating local environmental change with disease dynamics, and none involve motile marine fauna. A lethal, pathogenic virus has recently been discovered that infects juvenile Caribbean spiny lobster (Panulirus argus) in the Florida Keys, the first virus reported for any species of lobster. Transmission of the disease is primarily via contact and infectivity is associated with ontogeny; juvenile lobsters are susceptible to infection, adults are not. A remarkable facet of the disease is that it not only kills infected individuals, but also alters the behavior of healthy individuals who are normally social, but actively avoid contact with diseased conspecifics. The underlying causes for the emergence of the disease remain a mystery, but human-caused transformations of nursery habitat and declining water quality in south Florida preceded its emergence. One hypothesis is that deteriorating water quality, including that anticipated with Everglades restoration, acts as a subtle stressor that compromises lobster resistance to infection and facilitates the spread of disease. At the same time, poor water quality alters nursery habitat structure, thereby indirectly influencing disease dynamics by increasing host encounter rates and thus disease transmission. Potentially counter-balancing the effects of these environmental changes are ontogenetic shifts in host behavior, susceptibility to infection, and avoidance of diseased individuals that may constrain transmission of the disease. This project will include an ambitious program of laboratory, field, and modeling research with the goal of building a predictive understanding of the multifaceted role that diminished habitat integrity plays in the spread of a viral disease among social animals in degraded coastal marine ecosystems. The project builds on prior NSF sponsorship and draws together the talents of a multidisciplinary group of scientists with experience in lobster biology, ecological modeling, invertebrate pathology, and molecular biology. Although the focus is on the emerging PaV1 virus in spiny lobster in Florida as a model system, the results of this project will provide a better understanding of the role of habitat structure, ontogenetic changes in host resistance, and host behavior in regulating disease transmission in natural populations subject to anthropogenic insult. The project objectives are: (1) To explore the underlying mechanisms that control the spread of disease and to predict viral prevalence in relation to changes in nursery habitat structure and water quality stressors by incorporating ontogenetic aspects of host behavior, susceptibility to disease, and disease transmission into the existing spatially-explicit, individual-based lobster population model. (2) To quantitatively test in mesocosm and field experiments the effect of altered nursery habitat structure on ontogenetic differences in host movement, host spatial distribution, and viral transmission. (3) To determine in laboratory experiments whether potential environmental stressors such as extreme temperatures and salinities, or poor water quality alter host suceptiblity to viral infection or infectivity. (4) To characterize in a laboratory study host disease states and to determine their prevalence in nature using molecular and histological techniques. Broader Impacts: This project will include continued involvement and cross-training of undergraduates, graduate students, and postdocs, including participation of undergraduates in NSF REU programs at VIMS and ODU. Association with local resource management agencies ensures that the basic science results of this project will find application in management decisions. The PIs will co-host a semi-annual one-day workshop in Key West for fishermen, scientists, environmental managers, and the interested public where recent scientific findings and environmental concerns in the Florida Keys will be discussed. Continued molecular work will yield new assays for detection of viral infected tissue, which may aid officials in monitoring the potential spread and shipment of infected lobsters around the world. Also, the modeling component will aid managers in predicting the spread of the disease in wild populations.