Data from: Recolonizing grey wolves increase parasite infection risk in their prey

The recent recolonization of Central Europe by the European grey wolf (Canis lupus) provides an opportunity to study the dynamics of parasite transmission for cases when a definitive host returns after a phase of local extinction. We investigated whether a newly established wolf population increased the prevalence of those parasites in ungulate intermediate hosts representing wolf prey, whether some parasite species are particularly well adapted to wolves, and the potential basis for such adaptations. We recorded Sarcocystis species richness in wolves and Sarcocystis prevalence in ungulates harvested in study sites with and without permanent wolf presence in Germany using microscopy and DNA metabarcoding. Sarcocystis prevalence in red deer (Cervus elaphus) was significantly higher in wolf areas (79.7%) than in control areas (26.3%) but not in roe deer (Capreolus capreolus) (97.2% vs. 90.4%) or wild boar (Sus scrofa) (82.8% vs. 64.9%). Of 11 Sarcocystis species, S. taeniata and S. grueneri occurred more often in wolves than expected from the Sarcocystis infection patterns of ungulate prey. Both Sarcocystis species showed a higher increase in prevalence in ungulates in wolf areas than other Sarcocystis species, suggesting that they are particularly well adapted to wolves, and are examples of ‘wolf specialists’. Sarcocystis species richness in wolves was significantly higher in pups than in adults. ‘Wolf specialists’ persisted during wolf maturation. The results of this study demonstrate that (1) predator–prey interactions influence parasite prevalence, if both predator and prey are part of the parasite life cycle, (2) mesopredators do not necessarily replace the apex predator in parasite transmission dynamics for particular parasites of which the apex predator is the definitive host, even if meso– and apex predators were from the same taxonomic family (here: Canidae, e.g. red foxes Vulpes vulpes), and (3) age–dependent immune maturation contributes to the control of protozoan infection in wolves.欧洲灰狼（Canis lupus）近期重新定居中欧地区，为研究终末宿主（definitive host）在局部灭绝后重新恢复时的寄生虫传播动态提供了绝佳研究契机。 本研究旨在探究三个核心问题：其一，新建立的灰狼种群是否提升了作为其猎物的有蹄类中间宿主（intermediate host）的寄生虫感染率；其二，是否存在特定寄生虫物种对灰狼形成了高度适应性；其三，这类适应性的潜在机制。本研究通过显微镜观测与DNA宏条形码（DNA metabarcoding）技术，在德国境内设有永久狼群定居与无狼群定居的研究区域中，分别统计了灰狼体内肉孢子虫（Sarcocystis）的物种丰富度，以及猎获有蹄类动物的肉孢子虫感染率。 马鹿（Cervus elaphus）在狼群活动区域的肉孢子虫感染率（79.7%）显著高于对照区域（26.3%）；但狍（Capreolus capreolus）（97.2% vs 90.4%）与野猪（Sus scrofa）（82.8% vs 64.9%）的感染率未出现显著差异。 在11种肉孢子虫中，带形肉孢子虫（S. taeniata）与格鲁内尔肉孢子虫（S. grueneri）在灰狼体内的检出率，高于基于有蹄类猎物的肉孢子虫感染模式所预期的水平。相较于其他肉孢子虫物种，这两种肉孢子虫在狼群活动区域的有蹄类宿主中感染率提升幅度更为显著，提示它们对灰狼形成了高度特异性适应，可归类为‘灰狼专性寄生虫’。灰狼幼崽体内的肉孢子虫物种丰富度显著高于成年个体，且‘灰狼专性寄生虫’在灰狼成长过程中持续存在。 本研究结果证实：其一，若捕食者与猎物均为某寄生虫生活史的组成部分，则捕食者-猎物相互作用会影响寄生虫感染率；其二，对于以顶级捕食者（apex predator）为终末宿主的特定寄生虫而言，即便中型捕食者（mesopredator）与顶级捕食者同属一个分类科（本研究中为犬科，例如赤狐Vulpes vulpes），中型捕食者也未必能在寄生虫传播动态中替代顶级捕食者的作用；其三，年龄依赖的免疫成熟过程有助于控制灰狼体内的原生动物感染（protozoan infection）。