Three scientists who developed treatments against parasites have won the 2015 Nobel Prize in Physiology or Medicine.

Their discoveries "have provided humankind with powerful new means to combat these debilitating diseases that affect hundreds of millions of people annually. The consequences in terms of improved human health and reduced suffering are immeasurable," said the Swedish committee on Monday when announcing the award, which is worth about 8 million Swedish kronor (about $1 million) and will be split among the three recipients.

Half will go to William C. Campbell of Drew University in New Jersey and Satoshi Ōmura of Kitasato University in Japan, for the development of the drug avermectin, which treats river blindness, lymphatic filariasis, and other roundworm parasite infections.

The other half goes to Youyou Tu of the China Academy of Traditional Chinese Medicine, who discovered artemisinin, a drug against the malaria parasite that has saved many lives over the last decade.

About one-third of the world's population, particularly in sub-Saharan Africa and South Asia, are affected by parasitic worms. River blindness causes inflammation of the cornea, leading to blindness, and lymphatic filariasis, also known as elephantiasis, makes limbs swell and often leads to permanent disability. Avermectin treatment "is so successful that these diseases are on the verge of eradication, which would be a major feat in the medical history of humankind," the committee said.

Every year, more than 450,000 people, mostly children, die of malaria. The disease is caused by single-cell parasites and spread by mosquitos. Although parasites have developed resistance to artemisinin in many countries, when used in combination with other drugs it reduces malaria deaths by about 20%, the committee said. "For Africa alone, this means that more than 100,000 lives are saved each year."