Three scientists have been awarded the Nobel Prize in Physiology or Medicine for the discovery of treatments for diseases caused by parasites. William C. Campbell and Satoshi Omura won for developing the drug avermectin, which is used to treat the parasitic worms that cause river blindness and filariasis. Youyou Tu received the award for the discovery of artemisinin, a drug that has significantly reduced the death rate from malaria. The three share the $900,000 prize.
River blindness, also called onchocerciasis, is caused by a tiny worm that is spread by the bite of black flies. The worms cause skin infections in addition to blindness. Filariasis, which is sometimes called elephantiasis, is caused when microscopic worms block the lymphatic system and cause massive swelling to the legs or other parts of the body. Malaria, a mosquito-borne disease caused by single-cell parasites. It kills more than 450,000 people a year, most of them children.
Omura, a microbiologist, isolated avermectin from Streptomyces, bacteria that live in the soil. He isolated new strains of Streptomyces from soil samples and cultured them in the laboratory. One strain he isolated was Streptomyces avermitilis. Campbell, an expert in parasite biology, obtained the bacteria from Omura and found that it produced a substance that was very effective against parasites in animals. He purified it and named it avermectin, which was then modified to an even more effective compound called ivermectin.
Tu started looking for a better treatment for malaria in the1960s. She and her colleagues collected 380 extracts from 200 herbs used in traditional Chinese medicines. One of the plants they studied was sweet wormwood (Artemisia annua) which was used by Chinese herbalists centuries ago to treat fever. She found that artemisinin, a component of the artemesia herb, was effective against the parasites that cause malaria. The drug is now widely used in combination with other drugs and has reduced the mortality from malaria by more than 20% over all, and by more than 30% in children. Artemesinin saves more than 100,000 lives each year in Africa.