School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, United Kingdom.
Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain.
PeerJ. 2022 Feb 7;10:e12889. doi: 10.7717/peerj.12889. eCollection 2022.
The intensity of a pathogen infection plays a key role in determining how the host responds to infection. Hosts with high infections are more likely to transmit infection to others, and are may be more likely to experience progression from infection to disease symptoms, to being physiologically compromised by disease. Understanding how and why hosts exhibit variation in infection intensity therefore plays a major part in developing and implementing measures aimed at controlling infection spread, its effects, and its chance of persisting and circulating within a population of hosts. To track the relative importance of a number of variables in determining the level of infection intensity, we ran field-surveys at two breeding sites over a 12 month period using marked larvae of the common midwife toad () and their levels of infection with the amphibian pathogen (Bd). At each sampling occasion we measured the density of larvae, the temperature of the water in the 48 h prior to sampling, the period of time the sampled individual had been in the water body, the developmental (Gosner) stage and the intensity of Bd infection of the individual. Overall our data suggest that the temperature and the duration of time spent in the water play a major role in determining the intensity of Bd infection within an individual host. However, although the duration of time spent in the water was clearly associated with infection intensity, the relationship was negative: larvae that had spent less than 3-6 months in the water had significantly higher infection intensities than those that had spent over 12 months, although this infection intensity peaked between 9 and 12 months. This could be due to animals with heavier infections developing more quickly, suffering increased mortality or, more likely, losing their mouthparts (the only part of anuran larvae that can be infected with Bd). Overall, our results identify drivers of infection intensity, and potentially transmissibility and spread, and we attribute these differences to both host and pathogen biology.
病原体感染的强度在决定宿主如何对感染做出反应方面起着关键作用。感染程度较高的宿主更有可能将感染传播给他人，并且更有可能从感染发展为疾病症状，从而因疾病而在生理上受到损害。因此，了解宿主在感染强度上表现出差异的方式和原因，在制定和实施旨在控制感染传播、其影响以及其在宿主种群中持续存在和传播的机会的措施方面起着重要作用。为了追踪确定感染强度水平的多个变量的相对重要性，我们在 12 个月的时间里，在两个繁殖地点使用标记的普通蟾蜍幼虫（）及其感染两栖动物病原体（Bd）的水平进行了实地调查。在每次采样时，我们测量了幼虫的密度、采样前 48 小时水的温度、被采样个体在水体中的时间、个体的发育（戈斯纳）阶段和 Bd 感染的强度。总体而言，我们的数据表明，温度和在水中停留的时间长短在决定宿主个体的 Bd 感染强度方面起着重要作用。然而，尽管在水中停留的时间与感染强度明显相关，但这种关系是负相关的：在水中停留不到 3-6 个月的幼虫的感染强度明显高于在水中停留超过 12 个月的幼虫，尽管感染强度在 9 到 12 个月之间达到峰值。这可能是由于感染较重的动物发育得更快，死亡率更高，或者更有可能失去口器（唯一可能感染 Bd 的蛙类幼虫部位）。总体而言，我们的研究结果确定了感染强度的驱动因素，以及潜在的传染性和传播性，我们将这些差异归因于宿主和病原体生物学。
