SGER: Infectious Disease Ecology and Threatened Species: Impacts of West Nile Virus on Spotted Owl Populations

西尼罗河病毒(WNV)是一种蚊媒黄病毒，于1999年首次在北美东海岸传入，可在人类和野生动物，特别是鸟类中引起严重疾病。到2003年，西尼罗河病毒已在北美蔓延，首先出现在加利福尼亚州南部，到2004年秋季已蔓延到加利福尼亚州北部。西尼罗河病毒在加利福尼亚州北部的到来可能会对现有的鸟类群落产生深远的影响，这些鸟类群落对西尼罗河病毒的影响很幼稚。虽然已知该疾病会导致禽类死亡，但西尼罗河病毒对禽类种群的潜在影响在很大程度上尚不清楚。然而，最近两项关于鼠尾松鸡和美洲乌鸦野生种群的研究记录了直接可归因于西尼罗河病毒的年存活率分别下降了28%和72%。也有证据表明，猫头鹰可能特别容易感染西尼罗河病毒，因为它既通过蚊子直接传播，也通过受感染的猎物间接传播。目前在加利福尼亚州北部4个研究区对西点猫头鹰两个亚种的种群动态进行的长期研究为深入了解西尼罗河病毒的引入如何影响鸟类的种群动态提供了一个独特的机会。这些对斑点猫头鹰的长期研究收集了过去10到20年来标记个体的生存、繁殖力、招募和种群变化率的数据，这些数据提供了引入西尼罗河病毒之前的种群参数的基准值。使用标记重捕获估计器和正在进行的斑点猫头鹰研究的数据，这项研究项目将以不同的方式检查西尼罗河病毒的生态，以及这种新出现的疾病对斑点猫头鹰种群参数和种群变化率的影响。在这项提案中，我们要求在2005年，即西尼罗河病毒即将爆发的一年，研究西尼罗河病毒对其中一个研究人群的影响。这项建议要解决的总体问题是：1)在北方斑点猫头鹰栖息地感染西尼罗河病毒的流行率是多少？2)西尼罗河病毒对斑点猫头鹰的人口率有什么影响？以及3)猫头鹰领地西尼罗河病毒的直接和间接感染源的时空分布是什么？我们将通过收集蚊子、小哺乳动物和斑点猫头鹰种群的数据来解决这些问题。这项研究将由8名科学家组成的合作团队进行，其中包括2名从事斑点猫头鹰研究的野生动物种群生态学家、1名蚊子生态学家、3名在西尼罗河病毒方面有专长的野生动物疾病生态学家、1名病毒学家和1名熟悉模拟野生动物疾病动态的生物鉴定学家。此外，两名本科生将被纳入我们的研究计划，从而为学生提供不断增长的野生动物疾病生态学领域的培训。从长远来看，我们相信这个系统有希望预测西尼罗河病毒和其他引入的病原体对野生鸟类种群的影响。我们还相信，我们的研究可以为新出现的疾病对幼稚动物的潜在影响提供洞察，并进一步了解野生动物疾病系统的动态。

West Nile virus (WNV) is a mosquito-borne flavivirus that was first introduced on the east coast of North America in 1999 and can cause serious disease in humans and wildlife, especially birds. By 2003, WNV had spread across North America and first appeared in southern California and by fall 2004 had spread into northern California. The arrival of WNV in northern California could have profound impacts on the extant bird communities, which are naive to the effects of WNV. Although the disease is known to cause mortality in avian species, the potential impacts of WNV on avian populations are largely unknown. However, two recent studies on wild populations of sage grouse and American crows recorded 28% and 72% declines, respectively, in annual survival that were directly attributable to WNV. There is also evidence that owls may be particularly susceptible to WNV from both direct transmission by mosquitoes and indirect transmission from infected prey. Current long-term research on the population dynamics of two subspecies of spotted owls (Strix occidentalis) on 4 study areas in northern California offers a unique opportunity to provide insights on how the introduction of WNV affects avian population dynamics. These long-term studies on spotted owls have collected data on survival, fecundity, recruitment, and rates of population change from marked individuals for the past 10 to 20 years, which provides baseline values of population parameters prior to the introduction of WNV. Using mark-recapture estimators with data from the ongoing spotted owl studies, this research project will differentially examine the ecology of WNV and the effects of this emerging disease on population parameters and rates of population change in spotted owl populations. In this proposal, we are requesting funds to examine the effects of WNV on one of these study populations in 2005, a year with an impending outbreak of WNV. The overall questions to be addressed in this proposal are: 1) what is the prevalence of WNV infection in areas inhabited by northern spotted owls?, 2) what effect does WNV have on spotted owl demographic rates?, and 3) what is the spatial and temporal distribution of direct and indirect sources of infection of WNV in owl territories? We will address these questions by collecting data on mosquito, small mammal, and spotted owl populations. The research will be carried out by a collaborative team of 8 scientists, including 2 wildlife population ecologists conducting spotted owl research, a mosquito ecologist, 3 wildlife disease ecologists with expertise in WNV, a virologist, and a biometrician familiar with modeling wildlife disease dynamics. In addition, 2 undergraduate students will be included in our research program and, thus, provide training for students in the growing field of wildlife disease ecology. In the long-term, we believe this system has promise for predicting the effects of WNV and other introduced pathogens on wild avian populations. We also believe our research can provide insights into the potential impacts of emerging diseases on naive fauna, and further understanding of the dynamics of wildlifediseasesystems.