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Density-dependent effects on parasite growth and parasite-induced host immunodepression in the larval helminth Pomphorhynchus laevis

Published online by Cambridge University Press:  10 August 2010

STEPHANE CORNET*
Affiliation:
Université de Bourgogne, UMR CNRS 5561 Biogéosciences, Dijon, France Génétique et Evolution des Maladies Infectieuses, UMR CNRS-IRD 2724, Montpellier, France Centre d'Ecologie Fonctionnelle et Evolutive, UMR CNRS 5175, Montpellier, France
*
*Corresponding author: Génétique et Evolution des Maladies Infectieuses, UMR CNRS-IRD 2724, Centre de Recherche IRD, 911 av. Agropolis, BP 64501, 34394 Montpellier cedex 5, France. Tel: +33 4 67 41 63 73. Fax: +33 4 67 41 62 99. E-mail: Stephane.Cornet@ird.fr

Summary

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.

Information

Type
Research Article
Copyright
Copyright © Cambridge University Press 2010

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