Well, I just got a vampire whilst playing the DF Masterwork mod. I see no reason to open another thread for this and since this does seem to concern first vampire encounters, I'll leave mine here.
The creature that went by the name of Kolad Thocituzol kept drawing pentagrams all over the place which showed in the combat logs so I knew something was off. Didn't intend to do anything about it, though.
Eventually, the vampire somehow got into a fight with one of the mastiffs, "Mafol Tomus" as its owner called it, the only explanation I accept is that the mastiff sniffed out the unholy beast and bravely engaged it in combat.
Though, as it is with vampires, the proper kind tends to have supernatural strength and thus, Mafol was torn to pieces, drained of blood and quickly killed.
The foul beast , however, had the misfortune of revealing its true nature during combat. In the middle of my farms. During harvest time. The dwarves present quickly banded together and restrained the foul beast by sheer force of numbers until the woodcutters, attracted by the sound of combat, rushed into the farms and dismantled the beast to an extent that rendered it incapable of inflicting further harm on the populace.
The beast was finally vanquished as the mastiff Udib Vidangstigil, another mastiff and also a sibling of the killed Mafol Tomus latched onto the foul creature's head and crushed its skull with one forceful bite.
Now, if I didn't detect vampires by waiting until my mastiffs tear them to pieces, I'd propably try to weaponize them, too. Alas, maybe I'm luckier in a few years down the fort.
Edit:
Screw a few years down the fort. Pyromancers rolled in and saw that my fortress was festering with post-vampire epidemics, so they decided to purge it with fire.