From the Independent in the UK:
Are the wolves of Yellowstone National Park the first line of defense against a terrible disease that preys on herds of wildlife?
That is the question for a research project underway in the park, and preliminary results suggest that the answer is yes. Researchers are studying what is known as the predator cleansing effect, which occurs when a predator sustains the health of a prey population by killing the sickest animals. If the idea holds, it could mean that wolves have a role to play in limiting the spread of chronic wasting disease, which is infecting deer and similar animals across the country and around the world. Experts fear that it could one day jump to humans.