Beef, sheep and meat goat farmers know all about those. dewormer resistant worms aka parasites. Have to do integrated parasite control and treat only the animals needed to help prevent resistant parasites by overuse of dewormers.
The same has happened with antibiotics from over-prescribing them for every little cold or runny nose. I wonder if that is still the procedure with so many doctors and ER's, or have they wised up since?