at what temperature does syphilis die at?

I've been researching STD/Is lately and came across the work of Julius Wagner-Jauregg, where he used malaria fever to kill syphilis causing bacteria, my question is, at what temperature did the bacteria die at? since they should have been able to replicate such a fever without infecting someone with malaria. I can't seem to find at what temperature the bacteria would die at. just to be clear, I'm not looking for how high malaria fever can go, I mean the specific temperature the syphilis bacteria died at.

thank you in advance for your informative answers.