Three scientists who developed anti-parasitic drugs that have been used to successfully treat malaria, elephantiasis, and river blindness have won the 2015 Nobel Prize in Physiology or Medicine.

The discoveries, the Nobel Prize committee said in a press statement [PDF], "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."

Pharmaceutical chemist Youyou Tu, from the China Academy of Traditional Chinese Medicine, Beijing, was awarded half the prize for discovering a novel therapy for malaria based on the plant Artemisia annua, which she found after conducting a large-scale screening of herbal remedies used to treat malaria-infected animals—and then revisiting the ancient literature on herbal medicine for further clues about Artemisia annua's potential. Tu developed a purification procedure to render the active agent Artemisinin from the plant. Artemisinin is the key ingredient in a new class of antimalarial agents that rapidly kill the malaria parasites at an early stage of their development.

Now used worldwide to combat a disease infecting nearly 200 million people a year, Artemisinin is estimated to reduce mortality from malaria by more than 20 percent overall and by more than 30 percent in children. In Africa alone, Tu's medicine saves more than 100,000 lives every year.

The other half of the prize was awarded to two researchers whose development of a drug to treat infections caused by roundworm parasites has nearly eradicated two illnesses. Microbiologist Satoshi Ōmura, of Kitasato University, Tokyo, and William C. Campbell, of New Jersey's Drew University, developed the drug Avermectin from the soil-dwelling bacteria genus Streptomyces. Ōmura isolated 50 new strains of Streptomyces for further analysis, and Campbell, an expert in parasite biology, showed that a bioactive agent from one Streptomyces culture was "remarkably efficient" against parasites in domestic and farm animals. Purified and named Avermectin—also known by Ivermectin, its chemically modified, more potent form—this agent is the key component in a class of drugs that kill parasite larvae.

Today Ivermectin is used globally to fight parasitic diseases, especially to treat the one-third of the world's population affected by parasitic worms in sub-Saharan Africa, South Asia, and Central and South America. It's been so effective against river blindness (onchocerciasis) and lymphatic filariasis (elephantiasis) that "these diseases are on the verge of eradication, which would be a major feat in the medical history of humankind," as the committee noted.