No. Rakghouls come from sentient humanoids, not humans. In fact the Rakghoul plague can even infect non-sentient species like Reeks, Tarisian devourers and Mantellian Savrips. It's not endemic to humans.
Hmm... if memory serves me right, then the original plague, transmitted trough the Force by the Muur Talisman, only affected humans and a select few other species. That's why Zane's sidekick Gryph didn't turn, despite not being force sensitive.
But, if he would have been bitten, he would have turned, right?
Ok, looking at it from the other end:
If we permit other c-canon sources, then Taris eventualy got resettled at some point during the next 4 millenia. So either the republic got on top of the Rakghouls eventualy, or the problem somehow went away by itself.
Since you are so adamant to rule out conventional methods
, what unconventional
methods come to mind?