The Prime Directive is
...a guiding principle of the United Federation of Planets prohibiting the protagonists from interfering with the internal development of alien civilizations.
This is more about communicating with pre-warp societies.
In Star Trek: Discovery S1:E5 "Choose Your Pain", we hear:
Saru: I have much to attend to, and I could use your help with one thing.
Burnham: Of course.
Saru: Dr. Culber believes the Tardigrade is sentient. It remains in a state of cryptobiosis. We have no claim on its soul. Go save its life, Burnham. That's an order.
I'm trying to understand the ethical reasoning from a Star Trek perspective. Perhaps another directive applies.
My question is:
Does using Ripper in Star Trek: Discovery violate the prime directive?