It is known that lycanthropy (the werewolves' disease) is not only limited to all playable races, but also occurs among animals (werebeasts). You can't actually encounter werebeasts iirc, but they exist according to lore. However, I want to talk about vampirism. Like lycanthropy all playable races can contract vampirism, but can animals turn into vampires as well? I've seen multiple animals in-game being attacked with Vampiric Drain, the attack that causes vampirism, would that mean they can also become vampires?
I ran into something interesting a while back: a falmer I killed carried vampire dust on him, an ingredient usually only carried around by vampires. Now falmer may be considered humanoids (though I think the game treats them as animals), but I still thought it was quite interesting. There are multiple occassions in which falmer live in ruins that are also visited by mages and bandits (so possibly vampires too). Would it be possible for animals to become vampires too? Not necessarilly in the main game, but in the lore (like in some books, for example).

Falmer are still elves and could be infected I think as on vampires. Vampires in Skyrim are the boring main one there a lot of types that border on creatures or spirits themselves. Not sure if that answers anything but yeah you do seem to have animal vampires