Although the determinants of parasite diversity have been greatly investigated in the last decade thanks to the development of comparative methods,parasite diversity has only recently been viewed as ecological and evolutionary forces on their hosts.Recent investigations have explored new determinants of parasite diversity with special attention to the scale of observation (local,regional) and the metric used.If parasite diversity is unevenly distributed among host species,including rodents,the causes and consequences of this observation are not fully understood.Parasites are by definition strongly dependent on their hosts,and empirical and theoretical studies have emphasized the adaptation of parasites through maximization of their transmission success,but mostly in single host-single parasite systems.As hosts face multi-parasitism,this implies that hosts should respond and adapt to the whole parasite diversity.The first aim of this presentation is to summarize the determinants of parasite (both macro-and micro-) species richness and to identify the gaps in our knowledge,according to epidemiological processes,host ecology and host biogeography taking into account phylogenetic influences.The second aim is to give an overview of this asymmetry in host-parasite interactions and how parasite diversity affects the evolution of host life-traits and defense mechanisms.Finally,we will discuss how taking into account the evolutionary ecology of host-parasite interactions may contribute to disease ecology with an emphasis on rodent-borne diseases.