Dirofilaria repens transmission in southeastern Finland

Background: The spread of vector-borne diseases to new regions has become a global threat due to climate change, increasing traffic, and movement of people and animals. Dirofilaria repens, the canine subcutaneous filarioid nematode, has expanded its distribution range northward during the last decades. The northernmost European locations, where the parasite life-cycle has been confirmed, are Estonia and the Novgorod Region in Russia. Results: Herein, we describe an autochthonous D. repens infection in a Finnish woman. We also present two cases of D. repens infection in imported dogs indicating the life-cycle in the Russian Vyborg and St Petersburg areas, close to the Finnish border. Conclusions: The most obvious limiting factor of the northern distribution of D. repens is the summer temperature, due to the temperature-dependent development of larvae in vectors. With continuing climate change, further spread of D. repens in Fennoscandia can be expected.