Utilisation of rodent species by larvae and nymphs of hard ticks (Ixodidae) in two habitats in NE Poland.

The impact of host identity and habitat type on the density of hard ticks (Ixodes ricinus and Dermacentor reticulatus) infections on rodents in forest and abandoned field habitats in NE Poland was investigated. Ixodes ricinus was most abundant in the forest system, but D. reticulatus, although rarer, was most abundant in the field system. Environmental humidity and the much lower density of rodents probably limited the abundance of I. ricinus larvae in the field system, although this tick was still common on Microtus oeconomus from around small ponds. Nymphs of I. ricinus were comparatively rare in the forest, probably because of infection of non-rodent hosts. Dermacentor reticulatus nymphs on the other hand were very much more common in the ears of Microtus species than would have been predicted based on larval densities. The impact of habitat change (in this case successional change following field abandonment) on tick densities is emphasised, and the role of Apodemus as an epidemiological bridge, linking woodland and field habitats, is highlighted.