Models of parasite biocoenosis dynamic: host density and gastrointestinal parasites in alpine chamois

Host density is an important and widely accepted factor influencing microparasites epidemiology. In theory, host density would influence also macroparasite dynamic, although it would be achieved indirectly due to the presence of free-living infective stages of parasites. On this basis, it is expected that macroparasite abundance and prevalence would increase as host density increases, due to the higher probability for a new host to acquire infections from the environment. Nevertheless, some surveys indicate a negative relationship between host density and gastrointestinal helminth abundance in alpine chamois. On the basis of data collected from three different chamois populations, the Authors discuss the possibility that ecological factors different from host density should influence parasite biocoenosis dynamic, leading to the pattern observed in natural chamois-parasite systems.