Department of Biology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK.
Hakai Institute, End of Kwakshua Channel, Calvert Island, BC Canada, V0N 1M0.
Philos Trans R Soc Lond B Biol Sci. 2023 Mar 27;378(1873):20220018. doi: 10.1098/rstb.2022.0018. Epub 2023 Feb 6.
As a result of global change, hosts and parasites (including pathogens) are experiencing shifts in their thermal environment. Despite the importance of heat stress tolerance for host population persistence, infection by parasites can impair a host's ability to cope with heat. Host-parasite eco-evolutionary dynamics will be affected if infection reduces host performance during heating. Theory predicts that within-host parasite burden (replication rate or number of infecting parasites per host), a key component of parasite fitness, should correlate positively with virulence-the harm caused to hosts during infection. Surprisingly, however, the relationship between within-host parasite burden and virulence during heating is often weak. Here, we describe the current evidence for the link between within-host parasite burden and host heat stress tolerance. We consider the biology of host-parasite systems that may explain the weak or absent link between these two important host and parasite traits during hot conditions. The processes that mediate the relationship between parasite burden and host fitness will be fundamental in ecological and evolutionary responses of host and parasites in a warming world. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.
由于全球变化，宿主和寄生虫（包括病原体）正在经历其热环境的转变。尽管热应激耐受对宿主种群生存至关重要，但寄生虫感染会削弱宿主应对热的能力。如果感染降低了宿主在加热过程中的性能，宿主-寄生虫生态进化动态将受到影响。理论预测，寄生虫在体内的负担（复制率或每个宿主感染的寄生虫数量），是寄生虫适应度的一个关键组成部分，应该与毒力呈正相关-即在感染过程中对宿主造成的伤害。然而，令人惊讶的是，在加热过程中，寄生虫在体内的负担与毒力之间的关系往往很弱。在这里，我们描述了目前关于寄生虫在体内的负担与宿主热应激耐受之间联系的证据。我们考虑了宿主-寄生虫系统的生物学，这些生物学可能解释了在热条件下这两个重要的宿主和寄生虫特征之间的弱或不存在的联系。在一个变暖的世界中，调节寄生虫负担与宿主适应性之间关系的过程将是宿主和寄生虫生态和进化反应的基础。本文是主题为“变化世界中的传染病生态学和进化”的一部分。
