Key Concept: A zoonotic disease is one that transmits from animals to humans.
Why it's correct: Brucellosis (caused by Brucella species) spreads to humans via infected milk or contact with aborted fetal material, causing undulant fever — a classic textbook zoonosis, controlled by vaccination (S19) and pasteurization.
Why others fail: Mastitis, foot rot, and bloat are production/health issues confined to the animal itself — none of them spread to or infect humans.