Gulls are ubiquitous in urban areas due to a growing reliance on anthropogenic feeding sites, which has led to changes in their abundance, distribution, and migration ecology, with implications for disease transmission. Gulls offer a valuable model for testing hypotheses regarding the dynamics of influenza A virus (IAV) – for which gulls are a natural reservoir in urban areas. We sampled sympatric populations of Ring-billed (Larus delawarensis), Herring (L. argentatus), and Great Black-backed Gulls (L. marinus) along the densely populated Atlantic rim of North America to understand how IAV transmission is influenced by drivers such as annual cycle, host species, age, habitat type, and their interplay. We found that horizontal transmission, rather than vertical transmission, played an outsized role in the amplification of IAV due to the convergence of gulls from different breeding grounds and age classes. We detected overlapping effects of age and season in our prevalence model, identifying juveniles during autumn as the primary drivers of the seasonal epidemic in gulls. Gulls accumulated immunity over their lifespan, however short-term fluctuations in seroprevalence were observed, suggesting that migration may impose limits on the immune system to maintain circulating antibodies. We found that gulls in coastal urban habitats had higher viral prevalence than gulls captured inland, correlating with higher richness of waterbird species along the coast, a mechanism supported by our movement data. The peak in viral prevalence in newly fledged gulls that are capable of long-distance movement has important implications for the spread of pathogens to novel hosts during the migratory season as well as for human health as gulls increasingly utilize urban habitats.

中文翻译：

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年龄和季节预测城市海鸥的甲型流感病毒动态：非自然景观中自然宿主的后果

由于越来越依赖人为觅食地点，海鸥在城市地区无处不在，这导致它们的数量、分布和迁徙生态发生变化，对疾病传播产生影响。海鸥为检验有关甲型流感病毒 (IAV) 动态的假设提供了一个有价值的模型——海鸥是城市地区的天然宿主。我们对环嘴 ( Larus delawarensis )、鲱鱼 ( L. argentatus ) 和大黑背鸥 ( L. marinus ) 的同域种群进行了采样) 沿北美人口稠密的大西洋边缘了解 IAV 传播如何受到驱动因素的影响，例如年周期、宿主物种、年龄、栖息地类型及其相互作用。我们发现，由于来自不同繁殖地和年龄级别的海鸥会聚，水平传播而不是垂直传播在 IAV 的放大中发挥了巨大的作用。我们在患病率模型中检测到年龄和季节的重叠影响，确定秋季幼鸟是海鸥季节性流行的主要驱动因素。海鸥在其一生中积累了免疫力，但观察到血清阳性率的短期波动，这表明迁移可能会对免疫系统施加限制以维持循环抗体。我们发现沿海城市栖息地的海鸥比内陆捕获的海鸥具有更高的病毒流行率，这与沿海水鸟物种的丰富度相关，这是我们的运动数据支持的机制。由于海鸥越来越多地利用城市栖息地，新羽化海鸥的病毒流行高峰对迁徙季节病原体向新宿主的传播以及人类健康具有重要意义。