Résumé
A deterministic model was constructed to study the infestation of the snail Helix aspersa by a sexually transmitted nematode. The model was tuned to match experimental results and data gathered in the natural environment. An empirical relationship is thus observed between prevalence and abundance in a natural environment, and the intrinsic growth level of the parasite was estimated. The parasite is shown to be unable to regulate the host population in the absence of any biotic capacity. The estimated value of the basic transmission level shows that an infestation is easily maintained in a host population. Finally, the host-parasite system is globally stable with the measured parameters.