Leon A E, Fleming-Davies A, Adelman J S, Hawley D M
Department of Biological Sciences, Virginia Tech.
Department of Biology, University of San Diego.
bioRxiv. 2024 Oct 24:2024.10.21.619473. doi: 10.1101/2024.10.21.619473.
Pathogen reinfections occur widely, but the extent to which reinfected hosts contribute to ongoing transmission is often unknown despite its implications for host-pathogen dynamics. House finches () acquire partial protection from initial exposure to the bacterial pathogen (MG), with hosts readily reinfected with homologous or heterologous strains on short timescales. However, the extent to which reinfected hosts contribute to MG transmission has not been tested. We used three pathogen priming treatments- none, intermediate (repeated low-dose priming), or high (single high-dose priming)-to test how prior pathogen priming alters the likelihood of transmission to a cagemate during index bird reinfection with a homologous or heterologous MG strain. Relative to unprimed control hosts, the highest priming level strongly reduced maximum pathogen loads and transmission success of index birds during reinfections. Reinfections with the heterologous strain, previously shown to be more virulent and transmissible than the homologous strain used, resulted in higher pathogen loads within high-primed index birds, and showed higher overall transmission success regardless of host priming treatment. This suggests that inherent differences in strain transmissibility are maintained in primed hosts, leading to the potential for ongoing transmission during reinfections. Finally, among individuals, transmission was most likely from hosts harboring higher within-host pathogen loads, while associations between disease severity and transmission probability were dependent on a given bird's priming treatment. Overall, our results indicate that reinfections can result in ongoing transmission, particularly where reinfections result from heterologous and highly transmissible strains, with key implications for virulence evolution.
病原体再次感染广泛存在，但尽管再次感染的宿主对持续传播的影响关系到宿主-病原体动态变化，但其在持续传播中所起的作用程度往往未知。家朱雀（）初次接触细菌性病原体（MG）后会获得部分保护，宿主在短时间内很容易被同源或异源菌株再次感染。然而，再次感染的宿主对MG传播的作用程度尚未得到验证。我们采用了三种病原体预处理方式——无预处理、中等程度（重复低剂量预处理）或高强度（单次高剂量预处理）——来测试先前的病原体预处理如何改变在用同源或异源MG菌株对指示鸟进行再次感染期间将病原体传播给同笼伙伴的可能性。相对于未预处理的对照宿主，最高预处理水平在再次感染期间显著降低了指示鸟的最大病原体载量和传播成功率。用先前证明比所用同源菌株更具毒性和传播性的异源菌株进行再次感染，导致高预处理水平的指示鸟体内病原体载量更高，并且无论宿主预处理方式如何，总体传播成功率都更高。这表明在预处理宿主中菌株传播性的固有差异得以维持，导致在再次感染期间存在持续传播的可能性。最后，在个体中，传播最有可能发生在体内病原体载量较高的宿主身上，而疾病严重程度与传播概率之间的关联取决于特定鸟类的预处理方式。总体而言，我们的结果表明再次感染可导致持续传播，特别是在再次感染由异源且高传播性菌株引起的情况下，这对毒力进化具有关键意义。
