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

BACKGROUND: The mosquito-borne zoonotic parasite Dirofilaria immitis continues to spread northwards in Europe. This parasite can cause potentially life-threatening heartworm disease in dogs and pulmonary dirofilariasis in humans and is, therefore, a major health concern in both the veterinary medicine and human medical fields. This is the first report of D. immitis infections and heartworm disease in the Baltic country Estonia. METHODS: Data on canine D. immitis infections and heartworm disease were collected from the electronic patient records database of the Small Animal Clinic of Estonian University of Life Sciences, the only university clinic in Estonia. The patient records of dogs with confirmed diagnosis of D. immitis infection or heartworm disease were reviewed and summarised. RESULTS: Six dogs had been diagnosed with confirmed D. immitis infection or heartworm disease at the university clinic in 2021-2022. The confirmed diagnoses had been reached following international guidelines, based on a combination of different tests. Molecular confirmation of the parasite species had not been performed. Two of the dogs had been imported while four had no travel history outside of the country. CONCLUSIONS: 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.

Dirofilaria repens Microfilaremia in Three Dogs in Estonia.

In Europe, the zoonotic parasite Dirofilaria repens continues to spread northward. We describe three likely autochthonous canine microfilaremic D. repens infections from Estonia, an European Union country located in the Baltic region of northern Europe. The parasite species was confirmed with sequencing. These are new northernmost D. repens findings in Europe and show that the zoonotic parasite has spread farther north. Infection with D. repens should be included in the list of differential diagnoses for human and animal hosts also in northern Europe.