Susi Hanna, Vale Pedro F, Laine Anna-Liisa
Metapopulation Research Group, Department of Biosciences, University of Helsinki, P.O. Box 65 (Viikinkaari 1), FI-00014 Helsinki, Finland.
Am Nat. 2015 Aug;186(2):252-63. doi: 10.1086/682069. Epub 2015 Jun 4.
Variation in individual-level disease transmission is well documented, but the underlying causes of this variation are challenging to disentangle in natural epidemics. In general, within-host replication is critical in determining the extent to which infected hosts shed transmission propagules, but which factors cause variation in this relationship are poorly understood. Here, using a plant host, Plantago lanceolata, and the powdery mildew fungus Podosphaera plantaginis, we quantify how the distinct stages of within-host spread (autoinfection), spore release, and successful transmission to new hosts (alloinfection) are influenced by host genotype, pathogen genotype, and the coinfection status of the host. We find that within-host spread alone fails to predict transmission rates, as this relationship is modified by genetic variation in hosts and pathogens. Their contributions change throughout the course of the epidemic. Host genotype and coinfection had particularly pronounced effects on the dynamics of spore release from infected hosts. Confidently predicting disease spread from local levels of individual transmission, therefore, requires a more nuanced understanding of genotype-specific infection outcomes. This knowledge is key to better understanding the drivers of epidemiological dynamics and the resulting evolutionary trajectories of infectious disease.
个体层面疾病传播的变异已有充分记录，但在自然疫情中，这种变异的根本原因难以厘清。一般来说，宿主体内的复制对于确定受感染宿主释放传播繁殖体的程度至关重要，但导致这种关系变异的因素却鲜为人知。在此，我们以植物宿主窄叶车前（Plantago lanceolata）和白粉病菌（Podosphaera plantaginis）为研究对象，量化宿主基因型、病原体基因型以及宿主的共感染状态如何影响宿主体内传播（自感染）、孢子释放以及成功传播到新宿主（异感染）的不同阶段。我们发现，仅宿主体内传播无法预测传播率，因为宿主和病原体的基因变异会改变这种关系。它们的作用在疫情过程中会发生变化。宿主基因型和共感染对受感染宿主孢子释放的动态过程有特别显著的影响。因此，要从个体传播的局部水平可靠地预测疾病传播，需要对基因型特异性感染结果有更细致入微的理解。这一知识对于更好地理解流行病学动态的驱动因素以及传染病由此产生的进化轨迹至关重要。
