Host-parasite relationship and competition among parasites: a model for gastrointestinal nematodes of chamois.

A deterministic model considering the population dynamic of chamois and three parasite species (gastrointestinal nematodes) is presented. The model considers the logistic growth of host population, exploitation and/or interference competition among different parasite populations and intraspecific competition between parasite individuals. In vertebrates-parasites systems, intraspecific competition is well known and is probably mediated by host immunity. The sensitivity of the parameter alpha (representing the parasite induced host mortality) and the comparison with field data suggest that intraspecific competition plays an important role in determining host and parasites abundances and in stabilizing chamois-parasites relationship.