(CNN) The Nobel Prize for medicine has been jointly awarded this year to three scientists for their work on parasitic diseases.

Half of the award goes to Ireland’s William Campbell and Japan’s Satoshi Omura, who discovered a new drug to treat infections caused by roundworm parasites.

The other half goes to China’s Youyou Tu, who used traditional herbal medicine to find a new kind of antimalarial agent.

“Parasitic diseases affect the world’s poorest populations and represent a huge barrier to improving human health and well being,” the Nobel Assembly at Karolinska Institutet, which awards the Nobel Prize in physiology or medicine, said Monday.

“These two 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.”
Hindering the effects of roundworms

Campbell and Omura discovered a new drug, Avermectin, the derivatives of which “have radically lowered the incidence of River Blindness and Lymphatic Filariasis,” the Nobel Assembly said.

River blindness, or onchocerciasis, can cause vision impairment or blindness, nodules under the skin or debilitating itching, according to the Centers for Disease Control and Prevention.

Lymphatic filariasis, commonly known as elephantiasis, is a painful and extremely disfiguring disease, the World Health Organization said.

Thanks to Campbell and Omura, “Today the Avermectin-derivative Ivermectin is used in all parts of the world that are plagued by parasitic diseases,” the Nobel Assembly said.

“The importance of Ivermectin for improving the health and wellbeing of millions of individuals with River Blindness and Lymphatic Filariasis, primarily in the poorest regions of the world, is immeasurable. Treatment is so successful that these diseases are on the verge of eradication.”

The fight against malaria
Malaria is a mosquito-borne disease caused by parasites that invade red blood cells. It can cause fever and, in some cases, brain damage and death.

More than 450,000 people die every year from malaria, the Nobel Assembly said. Many of them are children.

And roughly half of the world’s population — 3.4 billion people — are at risk of contracting malaria.

The disease was traditionally treated by chloroquine or quinine, but by the late 1960s, efforts to eradicate malaria had failed and the disease was on the rise, the assembly said.

So Tu turned to traditional herbal medicine to try to tackle the disease. Using the plant Artemisia annua, she discovered a purification procedure that rendered an active agent called Artemisinin, the Nobel Assembly said.

“Artemisinin represents a new class of antimalarial agents that rapidly kill the Malaria parasites at an early stage of their development, which explains its unprecedented potency in the treatment of severe Malaria,” the assembly said.

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