Laboratorio de Ecología de Enfermedades, Instituto de Ciencias Veterinarias del Litoral, Universidad Nacional del Litoral - Consejo de Investigaciones Científicas y Técnicas (UNL - CONICET). Esperanza, Santa Fe, Argentina.
PLoS One. 2013 Jul 24;8(7):e70382. doi: 10.1371/journal.pone.0070382. Print 2013.
Parasites play a key role in regulating wildlife population dynamics, but their impact on the host appears to be context-dependent. Evidence indicates that a synergistic interaction between stress, host condition and parasites is implicated in this phenomenon, but more studies are needed to better understand this context-dependency. With the goal to assess the net effect of two types of chronic stress on various host-parasite interactions, we conducted an experiment in capybaras to evaluate the impact of food restriction and physical restraint on the infection intensity of specific gastrointestinal nematodes and coccidia, and how these stressors affected the growth, body condition, and some immuno-physiological parameters. Our hypothesis was that both forms of stress would result in an alteration in the host-parasite interactions, with deteriorated condition and reduced immunological investment leading to high parasite burdens and vice versa. Stressed capybaras had significantly higher coccidia infection intensities; but among individuals that were smaller, those stressed consistently showed lower helminth burdens than controls. Both stress treatments had a marked negative impact on growth and body condition, but concomitantly they had a significant positive effect on some components of the immune system. Our results suggest, on the one hand, that during prolonged periods of stress capybaras preventatively invest in some components of their immunity, such as innate humoural defenses and cells that combat helminths, which could be considered a stress-dependent prophylaxis. On the other hand, stress was found to cause greater infection intensities of protozoans but lower burdens of nematodes, indicating that the relationship between stress, physiological trade-offs and infection depends on the type of parasite in question. Moreover, both findings might be related in a causal way, as one of the immunological parameters enhanced in stressed capybaras is associated with the immune response to control helminths.
寄生虫在调节野生动物种群动态方面发挥着关键作用，但它们对宿主的影响似乎取决于具体情况。有证据表明，压力、宿主状况和寄生虫之间的协同相互作用与此现象有关，但需要更多的研究来更好地理解这种具体情况的依赖性。为了评估两种慢性压力对各种宿主-寄生虫相互作用的净效应，我们在水豚中进行了一项实验，以评估食物限制和身体束缚对特定胃肠道线虫和球虫感染强度的影响，以及这些应激源如何影响生长、身体状况和一些免疫生理参数。我们的假设是，这两种形式的压力都会导致宿主-寄生虫相互作用的改变，恶化的状况和减少的免疫投资会导致寄生虫负荷增加，反之亦然。应激水豚的球虫感染强度显著增加；但在体型较小的个体中，那些持续受到应激的个体的寄生虫负荷始终低于对照组。两种压力处理都对生长和身体状况产生了显著的负面影响，但同时它们对免疫系统的某些成分产生了显著的积极影响。我们的研究结果表明，一方面，在长时间的压力下，水豚会预防性地投资于其免疫系统的某些成分，如先天的体液防御和抵抗寄生虫的细胞，这可以被视为一种依赖于压力的预防措施。另一方面，压力被发现会导致原生动物的感染强度增加，但线虫的负荷降低，这表明压力、生理权衡和感染之间的关系取决于所涉及的寄生虫类型。此外，这两种发现可能以因果关系的方式相关，因为在应激水豚中增强的一个免疫参数与控制寄生虫的免疫反应有关。
