Terror Tuesday: Cross-Species Contamination

So badly wounded he could barely stand
Came Fenrir. The apothecary groaned
To see him. Werewolves, he'd said, should be banned.
Now here one was. "Please help me, Fenrir moaned
And held up one bright token that could not
E'er be rejected. He was hemorrhaging.
"Oh no! 'Tis a disaster! I have got
So little blood in stock!" "Doc, this thing --"
"Yes, yes, shut up. But all I have is Vlad.
I need more donors!" "Doc, you must obey --"
"I know. But this will be so very bad..."
But this transfusion did indeed take place,
And now a werewolf-vampire's ours to face.