Hoopers

From Earth Central

Hoopers are humans that live on Spatterjay and have been infected by the local leeches, and are as such almost immortal.

This is not be confused with "going native". Humans need to eat a certain amount of dome-grown foods instead of local wildlife (rhinoworms, boxies, etc), or they will at some point stop being human, like Spatterjay Hoop himself.