therianthropy n. Greek (therion, beast; anthropos, human or man): the metamorphosis of humans into animals, of which lycanthropy (werewolf-ism, if you will) is a subset.
Also, therianthrope n., one who has the ability to metamorphose into an animal.
Or, therianthropic adj., being partially bestial and partially human in form, especially used in discussion of deities such as those in the Egyptian pantheon.
The word can also be used in literature to describe figurative language describing humans in animal terms in almost the exact opposite way that 'personification' is used to describe figurative language attributing human qualities to non-human things.
Example of therianthropy as a literary device: "Come closer, darling," she purred.
(As opposed to personification: With its glaring, red 3:00AM, the clock mocked my inability to sleep.)
I am certain that Professor McGonagall was not born being able to turn into a cat, so I am sure that therianthropy can be learned.
I fail to see why a story about blood-suckers and therianthropes is so compelling for so many teenage girls.