Oronasal fistula in a 53-year-old hippopotamus (Hippopotamus amphibius).

An oronasal fistula is described in a 53-year-old captive hippopotamus, the animal having shown a nasal discharge, consisting mainly of food particles, during and after feeding for at least 15 years. Necropsy of the emaciated animal revealed an oronasal fistula, measuring 4.5 x 3.5 cm, adjacent to the third left molar tooth, the first and second molars being missing. The fistula was thought to have been caused by an earlier necrotizing alveolitis and osteitis. There was no evidence of rhinitis or aspiration pneumonia. Unrelated findings consisted of a follicular thyroid adenoma and generalized muscle atrophy.