Density-dependent effects on parasite growth and parasite-induced host immunodepression in the larval helminth Pomphorhynchus laevis.
نویسنده
چکیده
Larval helminths exploit the physiology of their intermediate hosts: first, as a resource for energy and space and second by altering the immune system activity to ensure their survival. Whereas the growth pattern under parasite competition has been investigated, the effect of multiple infections on the level of parasite-induced immunodepression in a trophically transmitted helminth has been neglected. In this study, amphipods Gammarus pulex were infected in the laboratory by the acanthocephalan Pomphorhynchus laevis to investigate how parasite density in the intermediate host affected (i) cystacanth growth and (ii) the level of parasite-induced alterations of the host immune defences, two traits strongly linked to host exploitation. The study highlights that sharing a host is costly. As parasite intensity increases, competition for resources translates into a reduction in cystacanth volume. Immune manipulation is also modulated by density. Interestingly, immunodepression is higher in double-infected hosts compared to hosts with a single infection, suggesting an opportunity for cooperative immune manipulation. However, in higher multiple infections, parasites do not further down-regulate the host immune response, possibly to avoid additional costs that may outweigh the benefits of immunodepression.
منابع مشابه
Variation and covariation in infectivity, virulence and immunodepression in the host-parasite association Gammarus pulex-Pomphorhynchus laevis.
Parasites often manipulate host immunity for their own benefit, either by exacerbating or suppressing the immune response and this may directly affect the expression of parasite virulence. However, genetic variation in immunodepression, which is a prerequisite to its evolution, and the relationship between immunodepression and virulence, have rarely been studied. Here, we investigated the varia...
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Many trophically-transmitted parasite larvae actively manipulate their intermediate host behaviour in ways increasing its transmission probabilities to the next host in their life cycle. Only stages infective for the next host alter host behaviour in such a way. Before reaching infectivity, parasite larvae grow into several larval stages in the intermediate host, all being non-infective for the...
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Besides conspicuous changes in behaviour, manipulative parasites may also induce subtle physiological effects in the host that may also be favourable to the parasite. In particular, parasites may be able to influence the re-allocation of resources in their own favour. We studied the association between the presence of the acanthocephalan parasite, Pomphorhynchus laevis, and inter-individual var...
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عنوان ژورنال:
- Parasitology
دوره 138 2 شماره
صفحات -
تاریخ انتشار 2011