Piggies - Nick Gifford

A freak storm transports Ben to a parallel world inhabited by vampires. He manages to escape to the woods where others like him (called ferals by the vampires) hide. As he begins to give up hope of ever getting home, Ben makes friends with Rachel, avampire more human than some of the ferals who treat him with suspicion. Rachel takes Ben to her farm in an attempt to prove that she's not like the other vampires, but that's when he discovers a terrible secret. And why is the book called PIGGIES? That's the worst horror of all.