血孢子虫是鸟类中最为常见的寄生虫之一，由感染血孢子虫引发的寄生虫病通常可导致鸟类宿主的适合度降低，甚至种群数量的快速下降。以鸟类为宿主的血孢子虫主要包括三个属，即疟原虫属（Plasmodium）、血液变形虫属（Haemoproteus）和住白细胞原虫属（Leucocytozoon）。由于具有较高的多样性、在世界范围内广泛分布、可感染大多数鸟类宿主，这些血孢子虫一直被作为动物生态学和疾病进化研究中一个理想的研究模型。作为食物链顶端的食肉动物，猛禽是生态环境变化的重要指示物种，对于维持生态系统平衡有着不可替代的作用，然而，由于种群密度较低且处于较高的营养级，猛禽对于人为干扰以及病原体的感染也更为敏感。因此，掌握其血孢子虫感染模式及影响因素不仅有助于我们理解鸟类宿主与血孢子虫之间的协同进化过程，也可以为这些物种的保护提供相关的科学支撑。在本研究中，我们以北京猛禽救助中心2007-2021年间收治的35种1539只野生猛禽为研究对象，通过血涂片镜检、巢式PCR以及荧光定量PCR等实验方法对北京地区猛禽血孢子虫的感染模式开展了系统的研究，并结合其生活史特征对影响这些猛禽血孢子虫感染风险的因素进行了探讨。此外，我们进一步探讨了昼夜行为节律的差异对猛禽-血孢子虫之间相互作用关系的影响。主要研究结果如下：

1. 基于血孢子虫线粒体条形码基因检测共在北京地区分布的猛禽中鉴定出91个血孢子虫谱系支，包括疟原虫属谱系支20个，血液变形虫属谱系支39个，住白细胞原虫属谱系支32个。其中超过60%的谱系支（n = 56）为首次报道，充分说明此前针对猛禽血孢子虫多样性的了解和认识还远远不够。北京地区猛禽血孢子虫的感染率为28.78%，其中疟原虫属血孢子虫的感染率最低，为5.72%，其次为住白细胞原虫属（10.27%），而血液变形虫属感染率最高（15.92%）。北京地区猛禽血孢子虫的感染率在不同季节之间存在显著差异，并随季节呈双峰型波动，主要由住白细胞原虫属血孢子虫主导（χ² = 109.28，df = 3，p < 0.01），疟原虫属血孢子虫和血液变形虫属血孢子虫季节波动呈相反趋势。血孢子虫感染率在不同的猛禽物种之间存在显著的差异（Fisher’ exact test，p < 0.01），同时，这种物种间的感染率差异与采样物种的样本量无关（Z = 1.26，p = 0.21）。

2. 在本研究测试的所有猛禽血孢子虫感染风险预测因子中，我们发现与宿主免疫相关的生物特征（体重、性别和猛禽物种间的系统发育关系）并不能很好的解释北京地区猛禽物种之间的血孢子虫感染率差异。相反，一些决定宿主与媒介接触频率的相关生物特征（年龄和昼夜活动模式）以及生态和生活史特征（巢型、地理分布范围以及迁徙距离）被证实是影响猛禽血孢子虫感染率的重要因素。我们进一步讨论了这些预测变量对于不同属血孢子虫感染率的决定作用。

3. 猛禽宿主昼夜行为节律的差异首先导致了不同的血孢子虫感染模式，夜行性猛禽的血孢子虫感染风险明显高于昼行性猛禽，同时，感染夜行性猛禽的血孢子虫以住白细胞原虫为主。然而，我们进一步的研究发现相比于夜行性猛禽，住白细胞原虫属血孢子虫在昼行性猛禽中的感染强度更高。这可能是由于在长期的相互作用过程中，夜行性猛禽对频繁感染它们的住白细胞原虫属血孢子虫已经产生了一定的适应和抵抗能力，因此对于住白细胞原虫属血孢子虫感染的抵抗能力也比昼行性猛禽更强。此外，感染昼行性猛禽和夜行性猛禽的血孢子虫谱系支在系统发育关系上并没有明显的分开。然而，相比于昼行性猛禽，夜行性猛禽与其感染的血孢子虫谱系支之间的宿主-寄生虫网络结构更加具有特异性，即存在更多一一对应的宿主-寄生虫联系，表明夜行性猛禽和感染它们的血孢子虫之间的相互作用更加具有特异性。

综上所述，本研究系统的研究了北京地区猛禽血孢子虫的感染模式，分析了猛禽血孢子虫感染风险的影响因素，并进一步探讨了昼夜活动节律的变化如何影响猛禽宿主及其所感染的血孢子虫之间的相互作用关系。

Haemosporidian is one of the most common parasites in bird species, parasitic diseases caused by haemosporidians usually lead to fitness loss, even a rapid decline of the host population. Avian haemosporidians are grouped taxonomically into three main genera: Plasmodium, Haemoproteus, and Leucocytozoon. Due to their high diversity, worldwide distribution and ability to infect most avian hosts, these haemosporidians have been used as an ideal research model in studies of animal ecology and disease evolution. As predators at the top of the food chain, raptors are important indicators of ecological change and play an irreplaceable role in maintaining the balance of the ecosystem, however, due to their low population density and high trophic level, raptors are also more sensitive to human disturbance and pathogenic infections. Therefore, understanding the infection patterns of haemosporidians in raptors and the factors affecting them will not only help us to understand the coevolution processes between avian hosts and haemosporidians, but also provide a relevant scientific support for the conservation of these species. In this study, we used 1539 wild raptors of 35 species admitted to the Beijing Raptor Rescue Centre between 2007 and 2021 to systematically investigate the infection pattern of raptor haemosporidians in Beijing by blood smear microscopy, nested PCR and Real-time quantitative PCR, and to investigate the factors affecting the risk of haemosporidians infection in these raptor species in relation to their life history characteristics. In addition, we further explored how circadian rhythm affect host-parasite associations. The main results are as follows:

1. A total of 91 haemosporidian lineages were identified in raptors distributed in Beijing based on mitochondrial barcode genetic testing, consisting of 20 Plasmodium, 39 Haemoproteus and 32 Leucocytozoon lineages. Over 60% of these lineages (n = 56) were reported for the first time, demonstrating that previous knowledge and understanding of the diversity of raptor haemosporidians is far from adequate. The total prevalence of haemosporidians in raptors in Beijing was 28.78%, with Plasmodium having the lowest prevalence of 5.72%, followed by Leucocytozoon (10.27%), and Haemoproteus having the highest prevalence (15.92%). The prevalence of haemosporidians in raptors in Beijing varied significantly between seasons, with a bimodal fluctuation with the season, dominated by Leucocytozoon (χ² = 109.28, df = 3, p < 0.01), there is an opposite trend in the seasonal fluctuations of Plasmodium and Haemoproteus. The prevalence of haemosporidians varied significantly between raptor species (Fisher’ exact test, p < 0.01), and this difference was independent of the sample size of the species sampled (Z = 1.26, p = 0.21).

2. Among all of the predictors for risk of haemosporidian infection in raptors tested in this study, we found that raptor species’ biological traits (Body mass, sex and phylogenetic relationships between raptor species) could not explain the differences of the risk of the total haemosporidian infection well. Instead, host traits related to the frequency of host-vector contact (Activity pattern, age, geographic range, migration distance and nest type) are proved to be the most robust predictors of the total haemosporidian infection rates within raptor hosts. We further discuss the role of these predictor variables in determining the risk of haemosporidian infection in different genera.

3. Differences in the circadian rhythm of raptor hosts firstly lead to different infection patterns of haemosporidians, nocturnal raptors have significantly higher risk of haemosporidian infection than diurnal raptors, while haemosporidians infecting nocturnal raptors are predominantly of the Leucocytozoon. However, our further study found that the infection intensity of Leucocytozoon was higher in diurnal raptors than in nocturnal raptors. This may be due to the fact that nocturnal raptors have developed some adaptation and resistance to frequent infections with Leucocytozoon over time, and therefore also more resistant to infection with Leucocytozoon than diurnal raptors. Furthermore, the lineages infecting the diurnal and nocturnal raptors were not clearly separated. However, the host-parasite network structure between nocturnal raptors and their haemosporidian lineages is more specific than that of diurnal raptors, i.e. there are more one-to-one host-parasite associations. This suggests that, as the only bird with nocturnal behaviour, the interactions between nocturnal raptors and the haemosporidians that infect them are more specific.

In conclusion, this study investigated the infection patterns of raptor haemosporidians in Beijing systematically, analysed the factors influencing the risk of raptor haemosporidians infection, and explored how changes in circadian activity rhythms affect the interaction between raptor hosts and the haemosporidians. The results of this study contribute to our understanding of the adaptive strategies of avian haemosporidians to different hosts and different environmental conditions and their co-evolutionary relationships with their avian hosts, as well as to our ability to predict and prevent the emerging infectious diseases.