Elsa Léger

Publications (8) View all

• Article: Changing distributions of ticks: causes and consequences.

  Elsa Léger, Gwenaël Vourc'h, Laurence Vial, Christine Chevillon, Karen D McCoy
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  ABSTRACT: Today, we are witnessing changes in the spatial distribution and abundance of many species, including ticks and their associated pathogens. Evidence that these changes are primarily due to climate change, habitat modifications, and the globalisation of human activities are accumulating. Changes in the distribution of ticks and their invasion into new regions can have numerous consequences including modifications in their ecological characteristics and those of endemic species, impacts on the dynamics of local host populations and the emergence of human and livestock disease. Here, we review the principal causes for distributional shifts in tick populations and their consequences in terms of the ecological attributes of the species in question (i.e. phenotypic and genetic responses), pathogen transmission and disease epidemiology. We also describe different methodological approaches currently used to assess and predict such changes and their consequences. We finish with a discussion of new research avenues to develop in order to improve our understanding of these host-vector-pathogen interactions in the context of a changing world.
  Experimental and Applied Acarology 01/2013; 59:219-244. · 1.39 Impact Factor
• Article: Population genetic structure and colonisation of the Western Antarctic Peninsula by seabird ticks Ixodes uriae

  McCOY, K.D, BEIS, BARBOSA, CUERVO, J.J, FRASER, W.R, GONZALEZ-SOLIS, JOURDAIN, POISBLEAU, QUILLFELDT, LEGER, DIETRIC
  Marine Ecology Progress Series 01/2012; · 2.71 Impact Factor
• Source

  Available from: Lucile Dianne

  Conference Proceeding: Poster : "An acanthocephalan parasite induces opposite host behavioural changes and predation probabilities according to its own developmental stage"

  Lucile Dianne, Marie-Jeanne Perrot-Minnot, Elsa Léger, Alexandre Bauer, Thierry Rigaud
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  ABSTRACT: Many trophically-transmitted parasites with complex life cycles manipulate their intermediate host behaviour in ways facilitating their transmission to final host by predation. This facilitation generally results from lowering host anti-predatory defences when the parasite is infective to the final host. Since non-infective parasite stages cannot successfully establish in the next host, a recent theoretical model showed that they should enhance their own survival (and thus increase their future transmission probabilities) by decreasing mortality risks of their host. Therefore, a parasite able to protect their host from predation when non-infective before switching to predation-increasing behavioural manipulation when infective should be selected. We tested this hypothesis in the acanthocephalan parasite Pomphorhynchus laevis in its intermediate host Gammarus pulex. Gammarids parasitized by non-infective stage of P. laevis (acanthella) hid significantly more under refuges than uninfected ones, before or after detecting predator cues. In addition, acanthella-infected gammarids were less predated upon by trout, a suitable final host, than uninfected gammarids. To our knowledge, this is the first study showing that such behavioural changes do indeed increase host survival, a necessary criterion to assign an adaptive value to this protective strategy. As predicted, a switch towards decreased anti-predatory behaviour of the host and enhanced vulnerability to predation was found when P. laevis reached the stage infective to its final host. The parasites appear to be able to exploit plasticity in host anti-predatory responses, and shift the host optimal response towards their own optimal balance. Consequences of such a protective strategy on host fitness are discussed.
  Jacques Monod Conference: "Coevolutionary arms race between parasite virulence and host immune defence: challenges from state of the art research", Roscoff, Brittany, France; 09/2011
• Source

  Available from: Lucile Dianne

  Article: Protection first then facilitation: a manipulative parasite modulates the vulnerability to predation of its intermediate host according to its own developmental stage.

  Lucile Dianne, Marie-Jeanne Perrot-Minnot, Alexandre Bauer, Mickaël Gaillard, Elsa Léger, Thierry Rigaud
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  ABSTRACT: Many trophically transmitted parasites with complex life cycles manipulate their intermediate host behavior in ways facilitating their transmission to final host by predation. This facilitation generally results from lowering host's antipredatory defenses when the parasite is infective to the final host. However, a recent theoretical model predicts that an optimal parasitic strategy would be to protect the intermediate host from predation when noninfective, before switching to facilitation when the infective stage is reached. We tested this hypothesis in the fish acanthocephalan parasite Pomphorhynchus laevis using the amphipod Gammarus pulex as intermediate host. Gammarids parasitized by noninfective stage of P. laevis (acanthella) hid significantly more under refuges than uninfected ones. In addition, acanthella-infected gammarids were less predated upon by trout than uninfected ones. As predicted, a switch toward decreased antipredatory behavior of G. pulex and enhanced vulnerability to predation was found when P. laevis reached the stage infective to its final host. The parasites appear to be able to exploit plasticity in host antipredatory responses, and shift the host optimal response toward their own optimal balance.
  Evolution 09/2011; 65(9):2692-8. · 5.15 Impact Factor
• Source

  Available from: Lucile Dianne

  Conference Proceeding: Poster: "Behavioural switch between host protection and host death during parasite ontogeny: challenging the parasitism-mutualism continuum"

  Lucile Dianne, Marie-Jeanne Perrot-Minnot, Elsa Léger, Alexandre Bauer, Thierry Rigaud
  [show abstract] [hide abstract]
  ABSTRACT: Many trophically-transmitted parasites with complex life cycle manipulate their intermediate host behaviour in ways facilitating their transmission to final host by predation, often by lowering host’s anti-predatory defences when infective to the final host. However, a recent theoretical model predicts that an optimal parasitic strategy would be to protect the intermediate host from predation when non infective, before switching to facilitation when the infective stage is reached. We tested this hypothesis in the fish acanthocephalan parasite Pomphorhynchus laevis using the amphipod Gammarus pulex as intermediate host. Gammarids parasitized by non-infective stage of P. laevis hid significantly more under refuges and were less preyed upon than uninfected ones. As predicted, a switch towards decreased anti-predatory behaviour of G. pulex and enhanced vulnerability to predation was found when P. laevis reached the stage infective to its final host. To our knowledge, this is the first study showing that such behavioural changes do indeed increase survival to predation risk, a necessary criterion to assign an adaptive value to this protective strategy. This study complements a previous one investigating intraspecific conflict between coinfecting infective and non-infective stages of P. laevis. We tested the hypothesis of a ‘sabotage’ of behavioural manipulation by the youngest non-infective parasite, and found that behavioural manipulation was slightly weakened but not cancelled in gammarids infected with mixed larval stages. Therefore, coinfecting infective and non-infective larvae both suffered competition, potentially resulting in delayed transmission and increased risk of mortality respectively. Both studies raised interesting questions about mechanisms underlying manipulation, and consequences of such strategies on host fitness.
  13th ESEB Congress (European Society for Evolutionary Biology), Tübingen, Germany; 08/2011