A nematode species from the Protostrongylidae family, unknown in the parasite fauna of Bulgaria until now, was found in the bronchi of a European brown hare (Lepus europaeus Pallas, 1778 L.) from a southwestern region of the country. At first the systematic identification of the found specimens was attributed to two possibilities-Protostrongylus terminalis Passerini (1884) Schulz, Orlow & Kutass, 1933 and Protostrongylus cuniculorum (Joyeux & Gaud, 1946) Schulz & Kadenazii, 1949. The autonomy of these two species was discussed based on data available in the literature. Morphological and morphometric data about the male and female specimens are provided in the present materials. After comparing these data with the ones available in the literature, the helminths were related to the species P. cuniculorum. P. cuniculorum is reported for the first time as part of the helminth fauna of the European brown hare from Southeastern Europe and Bulgaria in particular.
Keywords: European brown hare; Lepus europaeus L.; Morphometric features; Protostrongylus cuniculorum; Protostrongylus terminalis.