Small parasitic worms are beginning to defeat humanity’s ability to control them.
To use your example, dogs and hookworms. https://todaysveterinarypractice.com/parasitology/drug-resis...
To use your example, dogs and hookworms. https://todaysveterinarypractice.com/parasitology/drug-resis...
(Because, releasing billions of cats and dogs would leave them starving to death)