Heterogeneous hosts: how variation in host size, behaviour and immunity affects parasite aggregation
Heterogeneous hosts: how variation in host size, behaviour and immunity affects parasite aggregation
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DOI：
10.1111/1365-2656.12215
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发表时间：
2014-09-01
影响因子：
4.8
通讯作者：
Hoverman, Jason T.
中科院分区：
文献类型：
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作者：
Johnson, Pieter T. J.;Hoverman, Jason T.
1. 感染异质性是疾病生态学中最基本的模式之一，但令人惊讶的是，很少有研究通过实验探索其潜在的驱动因素。在这里，我们使用大规模的实地评估来评估寄生虫在两栖动物宿主种群中的聚集程度，然后采用一种新的实验方法来评估宿主大小、行为和免疫对繁殖这种异质性的潜在影响。在227个湿地、2468个宿主和7种寄生虫中，太平洋合唱蛙（Pseudacris regilla）种群内的宿主个体之间的感染持续聚集。各寄生虫感染负荷的对数均值和对数方差呈强线性关系（R-2: 0.91-0.98），斜率在1.37 ~ 1.67之间，相对于预期的统一泊松斜率，显示出聚集性。在对雷氏弓形虫和最毒吸虫（ondatraribeiroia）进行的实验室试验中，宿主免疫力（通过皮质酮暴露）或抗寄生虫行为（通过麻醉暴露）的实验性降低，使分离宿主的寄生虫感染负荷相对于未处理的个体增加了62-102%。在第二个旨在测试宿主免疫、行为和体型变化如何影响小群体（二组）内感染负荷变化的实验中，一个宿主免疫功能或行为的降低显著放大了群体内感染异质性，有效地使方差与平均比增加了一倍。然而，免疫仅在没有行为操纵的情况下影响聚集，而改变宿主的大小分布对聚集没有明显影响。使用泰勒幂律来整合现场和实验室数据，我们发现只有涉及行为减少的处理才能达到与自然宿主种群相当的聚集水平。因此，尽管持续时间短，但我们的治疗方法在感染负荷方面产生了与自然观察相似的异质性。这些结果强调，除了寄生虫暴露风险的外在变化外，个体宿主的一般属性，特别是行为，如何有可能影响感染成功和寄生虫聚集。持续整合跨空间、跨宿主物种和跨时间的感染异质性研究对理解和管理人类和野生动物疾病具有重要意义。
1. Infection heterogeneity is one of the most fundamental patterns in disease ecology, yet surprisingly few studies have experimentally explored its underlying drivers. Here, we used largescale field assessments to evaluate the degree of parasite aggregation within amphibian host populations followed by a novel experimental approach to assess the potential influence of host size, behaviour and immunity in reproducing such heterogeneity.2. Among 227 wetlands, 2468 hosts and seven parasite species, infections were consistently aggregated among host individuals within populations of the Pacific chorus frog (Pseudacris regilla). For each parasite species, the relationship between the log-mean and log-variance of infection load was strongly linear (R-2 : 0.91-0.98) with a slope between 1.37 and 1.67, indicative of aggregation relative to the expected Poisson slope of unity.3. In laboratory trials with P. regilla and the most virulent trematode (Ribeiroia ondatrae), experimental reductions in either host immunity (through corticosterone exposure) or antiparasite behaviours (through anaesthesia exposure) increased parasite infection loads in isolated hosts by 62-102% relative to unmanipulated individuals. In a second experiment designed to test how variation in host immunity, behaviour and body size affected variation in infection load within small groups (dyads), a reduction in immune function or behaviour of one host significantly amplified infection heterogeneity within the group, effectively doubling the variance-to-mean ratio. However, immunity affected aggregation only in the absence of behavioural manipulation, and changing the size distribution of hosts did not appreciably affect aggregation.4. Using Taylor's Power Law to integrate field and laboratory data, we found that only treatments involving behavioural reductions achieved aggregation levels comparable to natural host populations. Thus, despite their short duration, our treatments generated heterogeneity in infection loads similar to natural observations.5. These results emphasize how, alongside extrinsic variation in parasite exposure risk, individual host attributes generally and behaviour in particular have the potential to influence infection success and parasite aggregation. Continued integration of infection heterogeneity research across space, among host species, and over time has important implications for understanding and managing human and wildlife diseases.