Patterns of host specificity in parasites exploiting small mammals

Abstract

Host specificity is arguably one of the most important properties of a parasite, because it can determine, among other things, whether a parasite can survive the extinction of a host species, whether a parasite has the potential to invade new habitats such as islands, or whether a parasite can become established and spread following its introduction to a new geographical area. Macroparasites of micromammals have received relatively little attention in this regard. The available evidence suggests that some ecological features of small mammals may interact with parasite transmission mode to determine what levels of host specificity are observed. Still, large-scale patterns of host specificity have only been investigated in fleas, and studies on other parasite taxa are definitely needed. In addition, since many rodent species are now universal laboratory models in many branches of biology, it should prove possible to investigate host specificity in an experimental context. For instance, the mechanisms responsible for the failure or success of a particular parasite species in different host species could be examined using controlled laboratory infections. In addition, selection experiments like that of Gemmill et al. (2000) can be envisaged with host species like mice with short generation times, to track the evolution of host specificity under different selection regimes. The evolution and ecology of host specificity will remain an important research area for years to come. This is particularly true in the light of the global environmental changes occurring at present, and the possibility that, by altering transmission conditions, they will lead to the expansion of the host range of many parasite species.