MOE Key Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Zhejiang, China.
Molecular Ecology and Evolution Lab, Department of Biology, Lund University, Lund, Sweden.
Parasit Vectors. 2023 Jul 4;16(1):218. doi: 10.1186/s13071-023-05848-4.
Migratory birds play an important part in the spread of parasites, with more or less impact on resident birds. Previous studies focus on the prevalence of parasites, but changes in infection intensity over time have rarely been studied. As infection intensity can be quantified by qPCR, we measured infection intensity during different seasons, which is important for our understanding of parasite transmission mechanisms.
Wild birds were captured at the Thousand Island Lake with mist nets and tested for avian hemosporidiosis infections using nested PCR. Parasites were identified using the MalAvi database. Then, we used qPCR to quantify the infection intensity. We analyzed the monthly trends of intensity for all species and for different migratory status, parasite genera and sexes.
Of 1101 individuals, 407 were infected (37.0%) of which 95 were newly identified and mainly from the genus Leucocytozoon. The total intensity trend shows peaks at the start of summer, during the breeding season of hosts and during the over-winter season. Different parasite genera show different monthly trends. Plasmodium causes high prevalence and infection intensity of winter visitors. Female hosts show significant seasonal trends of infection intensity.
The seasonal changes of infection intensity is consistent with the prevalence. Peaks occur early and during the breeding season and then there is a downward trend. Spring relapses and avian immunity are possible reasons that could explain this phenomenon. In our study, winter visitors have a higher prevalence and infection intensity, but they rarely share parasites with resident birds. This shows that they were infected with Plasmodium during their departure or migration and rarely transmit the disease to resident birds. The different infection patterns of different parasite species may be due to vectors or other ecological properties.
候鸟在寄生虫的传播中起着重要作用，对当地鸟类或多或少有影响。以前的研究主要集中在寄生虫的流行率上，但寄生虫感染强度随时间的变化却很少被研究。由于感染强度可以通过 qPCR 来定量，我们在不同季节测量感染强度，这对于我们理解寄生虫传播机制很重要。
我们在千岛湖用网捕野生鸟类，并用巢式 PCR 检测禽血孢子虫感染。寄生虫使用 MalAvi 数据库进行鉴定。然后，我们使用 qPCR 来定量感染强度。我们分析了所有物种以及不同迁徙状态、寄生虫属和性别感染强度的逐月趋势。
在 1101 只个体中，有 407 只（37.0%）感染，其中 95 只为新鉴定种，主要来自 Leucocytozoon 属。总感染强度趋势在夏季开始时、宿主繁殖季节和越冬季节出现高峰。不同寄生虫属有不同的逐月趋势。疟原虫在冬季候鸟中引起高的流行率和感染强度。雌性宿主的感染强度有显著的季节性趋势。
感染强度的季节性变化与流行率一致。高峰期出现在早期和繁殖季节，然后呈下降趋势。春季复发和鸟类免疫力可能是解释这种现象的原因。在我们的研究中，冬季候鸟的流行率和感染强度较高，但它们很少与当地鸟类共享寄生虫。这表明它们在离开或迁徙时感染了疟原虫，很少将疾病传播给当地鸟类。不同寄生虫种的不同感染模式可能是由于媒介或其他生态特性造成的。
