Shoot an infected deer in the head or have it otherwise die violently on the ground. Prions can last in the soil for years and years. Misfolded proteins are basically invulnerable, even in shit like autoclaves. If cows eat grass that has prions on them, that shit could potentially jump. And a lot of people ranch their cattle on public lands where infected deer are, and where wolves are unavailable due to politicians, who would otherwise prevent infected deer from spreading.

The best thing that we can do is have wolves clamp down on the few infected deer immediately rather than generate large pools of infection that then start cross-contaminating domestic livestock. Prions and ebola are the two things that really keep me up at night.