You can never know for sure, I don't think, if you killed every last worm or not. I have not seen any for months & months & months though, & I do know really well how to check!
Initially for about 3 months I was expelling tons of them, at least 5 different kinds. I keep up ongoing maintainence to kill any that might be lurking or picked up anyway, thru daily use of diatomaceous earth & cayenne & Colloidal Silver , occasional use of Black-Walnut & Wormwood - I bought some quassia which I will use some time just to be on the safe side.
Also each day I wear a zapper at the ankle for about 70 min., & for 70 min. at the inside elbow - near all those veins - while at the computer.
They may not be all dead, but all the ones I killed will never reproduce again.