If you're "currently" feeding pre-killed, that means he's had worms for a long time...he had to get them from LIVE food. Poor snake! Worms rob the snake's body
of much-needed nutrients.
I have treated wild-caught snakes for worms before...not that hard, meds are pretty safe AND effective. Your vet can dose or show you how it's done- I've used
oral meds for this- not sure if there's any sort of injectable treatment now or not for snakes- as long as your vet has experience with snakes? -I hope!