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Journal of Theoretical Biology ] (]]]]) ]]]]]] Within-host evolution and virulence in microparasites

Summary: Journal of Theoretical Biology ] (]]]]) ]]]­]]]
Within-host evolution and virulence in microparasites
Jean-Baptiste Andre´ a,b,Ã, Bernard Godellea
Laboratoire Ge´nome, Populations, Interactions, Adaptation, USTL--IFREMER--CNRS UMR 5171,
Universite´ des Sciences et Techniques du Languedoc, Montpellier, France
Instituto Gulbenkian de Cie^ncia, Rua da Quinta Grande, 6 P-2780-156 Oeiras, Portugal
Received 16 September 2005; received in revised form 28 November 2005; accepted 5 December 2005
An important aspect of microparasite biology is the fact that infections are populations of thousands of microbes. As any population,
infections are hence subject to two main types of changes: demographic and evolutionary. Here we analyse the consequences of within-
host evolutionary changes. We build an epidemiological model where infections are regularly invaded by locally favored mutations
affecting various infectious traits (virulence, transmissibility and clearance). Our results are the following. In durable infections, where
within-host evolution is an important matter, a drop of transmissibility is only slightly deleterious to the infection, while a reduction of
infection lifespan is very costly. In consequence, locally favored mutations reducing transmissibility reach a larger frequency, or even the
complete fixation, and the suboptimality accumulated in infections owing to within-host evolution affects more their transmission than
their duration. Conversely, taking an infection at random and observing the events of within-host evolution, one is more likely to observe
reductions of infection length than reductions of transmissibility, because the mutations affecting transmissibility are often already
present in infections. We then discuss the interpretation of these results in terms of deleterious mutations, and we also emphasize that the


Source: André, Jean-Baptiste - CNRS & Université Pierre-et-Marie-Curie, Paris 6


Collections: Biology and Medicine