Data from: Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in sea otters along the Pacific Rim

Pathogens entering the marine environment as pollutants exhibit a spatial signature driven by their transport mechanisms. The sea otter (Enhydra lutris), a marine animal that lives much of its life within sight of land, presents a unique opportunity to understand land-sea pathogen transmission. Using a dataset on Toxoplasma gondii prevalence across sea otter range from Alaska to California, we found that the dominant drivers of infection risk vary depending upon the spatial scale of analysis. At the population level, regions with high T. gondii prevalence had higher human population density and a greater proportion of human-dominated land uses suggesting a strong role for population density of the felid definitive host of this parasite. This relationship persisted when a subset of data were analysed at the individual level: large-scale patterns in sea otter T. gondii infection prevalence were largely explained by individual exposure to areas of high human housing unit density, and other landscape features associated with anthropogenic land use, such as impervious surfaces and cropping land. These results contrast with the small-scale, within-region analysis, in which age, sex and prey choice accounted for most of the variation in infection risk, and terrestrial environmental features provided little variation to help in explaining observed patterns. These results underscore the importance of spatial scale in study design when quantifying both individual-level risk factors and landscape-scale variation in infection risk.

作为污染物进入海洋环境的病原体，其空间分布特征由其输运机制所驱动。海獭（Enhydra lutris）作为一生多数时间都栖息在近岸区域的海洋哺乳动物，为解析陆-海间的病原体传播提供了独特的研究契机。本研究依托覆盖阿拉斯加州至加利福尼亚州全域海獭栖息地的刚地弓形虫（Toxoplasma gondii）感染率数据集开展分析，结果显示感染风险的主导驱动因子会随分析所用的空间尺度发生变化。在种群尺度下，刚地弓形虫感染率较高的区域往往拥有更高的人口密度以及更大比例的人工主导土地利用类型，这表明该寄生虫的终末宿主——猫科动物的种群密度发挥了关键作用。当以个体为单位对部分数据集进行分析时，上述关联依然成立：海獭的刚地弓形虫感染率的宏观分布模式，在很大程度上可由个体暴露于高人口居住密度区域，以及其他与人为土地利用相关的景观特征（如不透水面、耕地）来解释。上述结果与小尺度区域内分析的结果形成鲜明对比：在小尺度区域分析中，年龄、性别以及猎物选择能够解释大部分感染风险的变异，而陆地环境特征对解释观测到的分布模式几乎无贡献。本研究结果凸显了在量化个体水平风险因子以及景观尺度感染风险变异的研究设计中，空间尺度的重要性。