Source : Webster's Revised Unabridged Dictionary (1913)

Zoanthropy \Zo*an"thro*py\, n. [Gr. ? animal + ? man.] (Med.)
   A kind of monomania in which the patient believes himself
   transformed into one of the lower animals.

Source : WordNet®

zoanthropy
     n : the delusion that you have assumed the form of an animal