Leon Ariel E, Hawley Dana M
Department of Biological Sciences, Virginia Tech, 2119 Derring Hall (0406), Blacksburg, VA, 24061, USA.
Ecohealth. 2017 Dec;14(4):793-804. doi: 10.1007/s10393-017-1261-x. Epub 2017 Aug 1.
Hosts in free-living populations can experience substantial variation in the frequency and dose of pathogen exposure, which can alter disease progression and protection from future exposures. In the house finch-Mycoplasma gallisepticum (MG) system, the pathogen is primarily transmitted via bird feeders, and some birds may be exposed to frequent low doses of MG while foraging. Here we experimentally determined how low dose, repeated exposures of house finches to MG influence host responses and protection from secondary high-dose challenge. MG-naive house finches were given priming exposures that varied in dose and total number. After quantifying host responses to priming exposures, all birds were given a secondary high-dose challenge to assess immunological protection. Dose, but not the number of exposures, significantly predicted both infection and disease severity following priming exposure. Furthermore, individuals given higher priming doses showed stronger protection upon secondary, high-dose challenge. However, even single low-dose exposures to MG, a proxy for what some birds likely experience in the wild while feeding, provided significant protection against a high-dose challenge. Our results suggest that bird feeders, which serve as sources of infection in the wild, may in some cases act as "immunizers," with important consequences for disease dynamics.
自由生活种群中的宿主在病原体暴露的频率和剂量方面可能会经历显著变化，这可能会改变疾病的进展以及对未来暴露的抵抗力。在家朱雀-鸡败血支原体（MG）系统中，病原体主要通过鸟类喂食器传播，一些鸟类在觅食时可能会频繁接触低剂量的MG。在这里，我们通过实验确定了家朱雀低剂量、重复接触MG如何影响宿主反应以及对二次高剂量攻击的抵抗力。未接触过MG的家朱雀接受了剂量和总数不同的初次暴露。在量化宿主对初次暴露的反应后，所有鸟类都接受了二次高剂量攻击以评估免疫保护。初次暴露后的感染和疾病严重程度主要由剂量而非暴露次数显著预测。此外，接受较高初次剂量的个体在二次高剂量攻击时表现出更强的保护作用。然而，即使是单次低剂量接触MG（这是一些鸟类在野外觅食时可能经历的情况），也能提供对高剂量攻击的显著保护。我们的结果表明，在野外作为感染源的鸟类喂食器，在某些情况下可能起到“免疫剂”的作用，对疾病动态产生重要影响。
