Evolutionary Ecology Group, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium.
Parasitology. 2011 Jul;138(8):1011-21. doi: 10.1017/S0031182011000618.
Virulence is part of the proximate base to the understanding of host-parasite interactions, and therefore it is crucial to interpret parasite-induced damage as an outcome of co-evolution between parasite and host. We experimentally investigated the impact of 2 congeneric ticks with contrasting transmission modes and host specificity, on the health of songbird nestlings (Parus major). The nidicolous Ixodes arboricola lives in tree holes where it obtains blood from adult birds and their nestlings, hence is prone to vertical transmission. All developmental stages of the field-dwelling Ixodes ricinus feed on different host taxa, hence are prone to horizontal transmission. Within each nest we infested 3 nestlings with varying loads of I. ricinus and 3 with Ixodes arboricola. Ixodes arboricola had no negative effects on nestling health (haematocrit, inflammation, body size, body condition). Body size was positively associated with the number of feeding I. arboricola adults. In contrast, I. ricinus infestations by nymphs and adult ticks led to haematocrit reductions. Furthermore, I. arboricola was a more prudent feeder, with longer feeding durations for smaller bloodmeals. Although the negative effects on nestling health were limited, our results are in line with current theories, stating that virulence increases with horizontal transmission, reduced dependence on individual hosts and reduced relatedness among co-exploiting ticks.
毒力是理解宿主-寄生虫相互作用的近因基础的一部分，因此，将寄生虫引起的损伤解释为寄生虫和宿主之间共同进化的结果至关重要。我们通过实验研究了两种具有不同传播模式和宿主特异性的同源蜱对鸣禽雏鸟（Parus major）健康的影响。树栖的 Ixodes arboricola 生活在树洞，从成年鸟类及其雏鸟身上吸血，因此容易垂直传播。田野居住的 Ixodes ricinus 的所有发育阶段都以不同的宿主类群为食，因此容易水平传播。在每个巢中，我们用不同数量的 I. ricinus 和 3 只 Ixodes arboricola 感染 3 只雏鸟。Ixodes arboricola 对雏鸟健康（红细胞压积、炎症、体型、身体状况）没有负面影响。体型与喂食的 I. arboricola 成虫数量呈正相关。相比之下，若幼虫和成年蜱虫寄生 I. ricinus 会导致红细胞压积降低。此外，Ixodes arboricola 是一种更谨慎的取食者，较小的血餐会延长取食时间。尽管对雏鸟健康的负面影响有限，但我们的结果与目前的理论一致，即毒力随着水平传播的增加、对个体宿主的依赖减少以及共同利用的蜱虫之间的亲缘关系降低而增加。
