Three scientists were awarded the Nobel Prize in Physiology or Medicine for their pioneering work on parasitic diseases, the Nobel committee announced Monday. William C. Campbell and Satoshi Omura were recognized for their work against infections caused by the roundworm parasite and developing the drug Avermectin. The pair shared the prize with Youyou Tu for her discovery of Artemisinin, a therapy against malaria. The Nobel committee said the work of the three changed the lives of hundreds of millions of people affected by these diseases. Malaria kills more than 450,000 people worldwide each year while parasitic worms affect a third of the world’s population and cause a number of illnesses.