First report of a naturally patent infection with Dirofilaria immitis in an otter (Lutra lutra).

Dirofilaria immitis causes a severe and life-threatening cardio-pulmonary disease in Europe, Asia, Africa, and the Americas; also, zoonotic infections have been reported. This parasitic vector-borne disease is mostly common in domestic and wild canids and felids. Here, we present a rare finding of this roundworm in the heart of a Eurasian otter (Lutra lutra). Four mature specimens of D. immitis were found in the right ventricle of the heart. Necropsy was performed after the animal was found road-killed in Eastern Serbia, close to the Danube River. Two heartworms were females, one was male and sex for one remained unidentified. Microfilariae were present in the uterus of one of the female heartworms, indicating that otters can act as reservoirs of dirofilariasis in the wild. This is the first report of a patent infection in a free-ranging otter.