Heartworm disease in domestic dogs in Estonia: indication of local circulation of the zoonotic parasite Dirofilaria immitis farther north than previously reported.

Four of the dogs with a confirmed D. immitis infection or heartworm disease had no history of being imported or travelling outside of the country, indicating autochthonous infections and, consequently, local circulation of the parasite in Estonia. These findings represent the new northernmost autochthonous cases of D. immitis infection and canine heartworm disease reported in the European Union.