In dwarf fortress, how can I use reactions or dfhack to make my adventurer a vampire?

I'm not sure what the command is in dfhack, but according to the wiki as of v42, you can become either a vampire or werewolf by toppling statues:

Becoming a vampire by toppling statues

As of v42 it is now additionally possible to become a vampire by toppling statues in a temple or sanctuary.

Walk up to the statue and topple it with u then a. Toppling a statue in this way will lead you to being cursed: the curse will be either Vampirism or Werebeast. Which curse you get appears to be randomly decided at the time you topple the statue (reloading the game and toppling it again has been confirmed to give the alternate curse.)