Heartworm Disease in Jackals: Unusual Location of Dirofilaria immitis

Purpose The knowledge of heartworm disease in free ranging wild canid populations is limited. As it is very difficult to monitor this disease in live animals, sporadic findings are mostly obtained by examining culled individuals of game species. Methods As a part of a broader study on jackal (Canis aureus) ecology in Serbia, the necropsy of legally hunted animals was performed in 2020. Results Two cases of heartworm infection with unusually located adult heartworms were diagnosed. The first case is an adult female jackal harvested in the vicinity of the capital city of Belgrade. Three adult specimens of Dirofilaria immitis were found in the right atrium of the heart, and nine adult specimens were located at an atypical site, in the vena cava caudalis. Very similar, the second case was in an adult female jackal harvested in the vicinity of Backi Monostor. In this case, six adult specimens of D. immitis were found in the right atrium of the heart and six more adult specimens in the vena cava caudalis. Conclusion Although this nematode generally resides in the pulmonary arteries and the right ventricle of the heart, rare findings in other large blood vessels can occur. To the best of our knowledge, these are the first and only two confirmed cases of adult D. immitis found in vena cava caudalis in jackals in Europe.