They are not returning they were just hiding real well from all the meds, herbs and ememas. They are on the run looking for a new hiding place like the lungs etc. a worm that size may have been hiding out in your liver or other organs. Little minute ones are return or new hatch. large one like that how long do you think it took to grow that size. keep working on building on immune system an making your blood and body not a nice place for them to hang out and reproduce.