Migration has an important impact on the transmission of pathogens. Migratory birds disperse parasites through their routes and may consequently introduce them to new areas and hosts. Hence, haemosporidian parasites, which are among the most prevalent, diverse and important bird pathogens, are potentially dispersed when infecting migrant hosts. Further, migrant hosts could enhance local parasite prevalence and richness by transporting new parasite strains to new areas. Here, we hypothesize and aim to evaluate if 1) migratory birds spread parasite lineages along their routes, and 2) localities crossed by more migratory birds have greater prevalence and richness of haemosporidians. For the first hypothesis, we tested whether parasite lineages found 1) in both migrants and residents, and 2) only in residents, differ in their frequencies of occurrence among localities. For the second hypothesis, we tested for a relationship among localities between the overall local haemosporidian parasite richness and prevalence, and the proportion of migratory bird individuals present in a locality. We combined a dataset on 13 200 bird samples with additional data from the MalAvi database (total: ~2800 sequenced parasites comprising 675 distinct lineages, from 506 host species and 156 localities) from South America, and used Bayesian multi-level models to test our hypotheses. We demonstrate that parasites shared between resident and migratory species are the most spatially widespread, highlighting the potential of migrants to carry and transmit haemosporidians. Further, the presence of migrants in a locality was negatively related to local parasite richness, but not associated with local prevalence. Here, we confirm that migrants can contribute to parasite dispersal and visiting migrants are present in regions with lower Plasmodium prevalence. Also, we observed their presence might raise Haemoproteus community prevalence. Therefore, we demonstrate migrants enhance pathogens spread and their presence may influence parasite community transmission.

中文翻译：

---

候鸟散播血孢子虫寄生虫并影响它们在鸟类群落中的传播

迁徙对病原体的传播有重要影响。候鸟通过它们的路线传播寄生虫，因此可能会将它们引入新的区域和宿主。因此，血孢子虫寄生虫是最普遍、最多样化和最重要的鸟类病原体之一，在感染迁徙宿主时可能会分散。此外，移民宿主可以通过将新的寄生虫菌株运送到新的地区来提高当地寄生虫的流行率和丰富度。在这里，我们假设并旨在评估是否 1) 候鸟沿其路线传播寄生虫谱系，以及 2) 候鸟越过的地区是否具有更高的血孢子虫流行率和丰富度。对于第一个假设，我们测试了寄生虫谱系是否在 1) 移民和居民中发现，2) 仅在居民中发现，不同地区出现的频率不同。对于第二个假设，我们测试了当地血孢子虫寄生虫总体丰富度和流行率与当地存在的候鸟个体比例之间的关系。我们将 13 200 只鸟类样本的数据集与来自南美洲的 MalAvi 数据库（总计：约 2800 个测序寄生虫，包括 675 个不同的谱系，来自 506 个宿主物种和 156 个地点）相结合，并使用贝叶斯多级模型来测试我们的假设。我们证明了常驻物种和迁徙物种之间共享的寄生虫在空间上分布最广，突出了移民携带和传播血孢子虫的潜力。此外，一个地方移民的存在与当地寄生虫丰富度呈负相关，但与当地流行率无关。在这里，我们确认移民可以促进寄生虫的传播，而来访的移民存在于较低的地区。疟原虫流行。此外，我们观察到它们的存在可能会提高Haemoproteus社区的流行率。因此，我们证明移民会增强病原体的传播，他们的存在可能会影响寄生虫社区传播。