They don't.
If you're looking for vampires and werewolves, the closest you can get is Thuringwethil, some monstrous bat creature, and when Sauron took on the form of a werewolf to fight...whatsisface. Beren. And Finrod.
Here's a lovelier version, with pictures:
http://fan.theonering.net/middleearthtours/berenandluthien.html
Not exactly the droids you were looking for.
Now Orc on the other hand, are the spawn of Morgoth surprise-buttraping them when it was too dark in middle-earth for anyone to see him coming.