On arrival at an accident and emergency ward, the woman had expressed her conviction and had spoken of feeling new sensations in her limbs.
Following a seizure, the thoughts no longer plagued the woman and she was said to be embarrassed by the episode, of which her memory was impaired.
Researchers from KU Leuven, a university in the Flemish city, writing in the Tijdschrift voor Psychiatrie medical journal suggest that such cases of zoanthropy, where a person believes they are an animal, have gone under-reported due to the difficulties patients face in explaining their thoughts.
There have been only 56 case descriptions in medical and historical literature in the period between 1850 to 2012.
Patients have reported believing they are a dog, lion, tiger, hyena, shark, crocodile, frog, bovine, cat, goose, rhinoceros, rabbit, horse, snake, bird, wild boar, gerbil and a bee.
She had suffered from depression since the death of a family member and that condition was prevalent among her relatives.
The research paper links the condition generally to underlying psychiatric disorders such as schizophrenia, psychotic depression and bipolar mood disorder. Symptoms of zoanthropy typically range from one hour to several decades.