Hasik Adam Z, Butt Shane, Maris Katie, Morris Sean, Morris Alison, Turner Richard S, Pemberton Josephine M, Albery Gregory F
Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
Department of Zoology, Trinity College Dublin, Dublin, Ireland.
Parasitology. 2025 Jun;152(7):724-734. doi: 10.1017/S0031182025100516.
Exposure to environmentally transmitted parasites should increase with population density due to accumulation of infective parasites in space. However, resource competition also increases with density, lowering immunity and increasing susceptibility, offering an alternative pathway for density-dependent infection. To test the relationships between these two processes and parasitism, we examined associations between host density, resource availability, immunity, and counts of 3 common helminth parasites using a long-term study of red deer. We found evidence that immunity increased with resource availability while parasite counts declined with immunity. We also found that greater density correlated with reduced resource availability, and while density was positively associated with both strongyle and tissue worm burdens, resource availability was independently and negatively associated with the same burdens. Our results support separate roles of density-dependent exposure and susceptibility in driving infection, providing evidence that resource competition is an important driver of infection, exacerbating effects of density-dependent increases in exposure.
由于感染性寄生虫在空间中的积累，接触环境传播寄生虫的几率应随种群密度增加而上升。然而，资源竞争也会随密度增加，降低免疫力并增加易感性，这为密度依赖性感染提供了另一条途径。为了测试这两个过程与寄生虫感染之间的关系，我们通过对马鹿的长期研究，检验了宿主密度、资源可用性、免疫力以及3种常见蠕虫寄生虫数量之间的关联。我们发现，免疫力随资源可用性增加而增强，而寄生虫数量随免疫力下降。我们还发现，更高的密度与资源可用性降低相关，虽然密度与圆线虫和组织内寄生虫负荷均呈正相关，但资源可用性与相同的负荷呈独立负相关。我们的结果支持了密度依赖性暴露和易感性在驱动感染方面的不同作用，证明资源竞争是感染的一个重要驱动因素，加剧了密度依赖性暴露增加的影响。
