Rabies in northeastern Europe--the threat from invasive raccoon dogs.

The red fox (Vulpes vulpes) is the main terrestrial wildlife rabies vector in Europe. However, recently the raccoon dog (Nyctereutes procyonoides)--an invasive species originating from East Asia--has become increasingly important as secondary host, especially in the Baltic States. This imposes problems on neighboring rabies-free countries (such as Finland), where the density of each of the two vector species on its own might be too low to sustain a long-term rabies epizootic, but the community of vectors could be large enough to support a rabies epizootic. In this modeling study, we analyzed rabies epizootics in a community of foxes and raccoon dogs. We focused on the impact of density and behavioral differences (hibernation) between the two vector species. We found that rabies could persist in the community, even if the disease would not spread in the single vector species because its density was too low. Epizootics in the community were stronger than expected for single species, and raccoon dogs were usually the major rabies host. If raccoon dog territory density was high, invasive raccoon dogs could even outcompete native foxes because of apparent competition via the rabies virus. The enhancement in disease risk and disease intensity caused by raccoon dogs suggests that current strategies to control wildlife rabies in Europe should be reviewed, and that oral rabies vaccination also should target raccoon dogs after they emerge from hibernation.