Abstract：
Pathogens have traditionally been studied in isolation within host systems; yet in natural settings they frequently coexist. This raises questions about the dynamics of co-infections and how host life-history traits might predict co-infection versus single infection. To address these questions, we investigated the presence of two parasites, a gut parasite (Isospora coccidians) and a blood parasite (Plasmodium spp.), in House Finches (Haemorhous mexicanus), a common passerine bird in North America. We then correlated these parasitic infections with various health and condition metrics, including hematological parameters, plasma carotenoids, lipid-soluble vitamins, blood glucose concentration, body condition, and prior disease history. Our study, based on 48 birds captured in Tempe, Arizona, US, in October 2021, revealed that co-infected birds exhibited elevated circulating lutein levels and a higher heterophil:lymphocyte ratio (H/L ratio) compared to those solely infected with coccidia Isospora spp. This suggests that co-infected birds experience heightened stress and may use lutein to bolster immunity against both pathogens, and that there are potentially toxic effects of lutein in co-infected birds compared to those infected solely with coccidia Isospora sp. Our findings underscore the synergistic impact of coparasitism, emphasizing the need for more co-infection studies to enhance our understanding of disease dynamics in nature, as well as its implications for wildlife health and conservation efforts.
摘要：
传统上，病原体是在宿主系统中单独研究的；但是在自然环境中，它们经常共存。这引发了关于共感染的动态以及宿主生活史特征如何预测共感染与单一感染的问题。为了解决这些问题,我们调查了两种寄生虫的存在，肠道寄生虫（Isosporacocidians）和血液寄生虫（疟原虫属。),在豪斯·芬奇(墨西哥血液)，北美常见的雀形目鸟。然后，我们将这些寄生虫感染与各种健康和状况指标相关联，包括血液学参数，血浆类胡萝卜素，脂溶性维生素，血糖浓度,身体状况,和既往疾病史。我们的研究,根据在坦佩捕获的48只鸟,亚利桑那,US,2021年10月，发现与仅感染球虫的禽类相比，共感染的禽类表现出循环叶黄素水平升高和嗜异粒细胞：淋巴细胞比率（H/L比率）较高。这表明共感染的鸟类会承受更高的压力，并可能使用叶黄素来增强对两种病原体的免疫力，与仅感染球虫的鸟类相比，叶黄素在共感染的鸟类中存在潜在的毒性作用。我们的研究结果强调了共同寄生的协同影响，强调需要进行更多的共感染研究，以增强我们对自然界疾病动力学的理解，以及它对野生动物健康和保护工作的影响。
