Parasitic diseases affect billions of people worldwide, mostly in the world’s poorest countries.
The Nobel Prize in Physiology or Medicine was awarded on Monday to three scientists who discovered treatments for two of the most devastating of such diseases.
Irish-born scientist William C. Campbell and Japanese scientist Satoshi Omura were jointly awarded half the prize for their discovery of a therapy to treat infections caused by roundworm parasites. Chinese scientist Youyou Tu received the other half for her discovery of a new therapy for Malaria.
Digging up a cure
Campbell and Omura discovered the drug Avermectin, a modified form of which has dramatically reduced cases of river blindness and lymphatic filariasis/elephantiasis (pictured above). It has also been effective against a growing number of other parasitic diseases.
Both are caused by parasitic worms, which afflict an estimated third of the world’s population and are most prevalent in sub-Saharan Africa, South Asia, and Central and South America.
River blindness (onchocerciasis), which afflicts at least 25 million people worldwide, causes chronic inflammation in the cornea that ultimately causes blindness. Lymphatic filariasis, which affects more than 120 million people, causes chronic swelling. It results in life-long stigmatizing and disabling symptoms such as elephantiasis (lymphedema), extreme enlargement of a part of the body caused by blockage of the lymphatic system, and scrotal hydrocele, or swelling of the scrotum caused by a fluid-filled sac around the testicle.
Ōmura, an expert in isolating natural products, isolated new strains of the soil bacteria Streptomyces, which are known to produce a wide array of antibacterial compounds (including Streptomycin, the first antibiotic treatment for tuberculosis). He grew thsounds of these strains in the lab, and selected 50 of the most promising to test further.
Campbell studied Omura’s strains and found that a component in one of them effectively killed parasites in household and farm animals. The compound, which was purified and named Avermectin, was later chemically modified to a more effective form called Ivermectin. Campbell and Omura’s work led to a new class of drugs that are extremely effective against the parasitic diseases above and others.
Today, Ivermectin is freely available and used in all places where parasitic diseases are found. It is so effective that these diseases are on the verge of being eradicated.
An old remedy, a new drug
Malaria — a disease that is caused by the Plasmodium parasite that infects red blood cells — causes fever, and in severe cases, brain damage and death.
It kills more than 450,000 people every year, mostly children. Worldwide, more than 3.4 billion people are at risk of contracting the disease.
Malaria was traditionally treated with the drug chloroquine, or quinine, but the parasite started becoming resistant to it and eradication efforts failed.
To develop a new drug in the 1960s, Chinese medical scientist Youyou Tu turned to old knowledge: traditional Chinese medicine. She screened many herbal remedies for malaria in animals, and found one, a compound found in the sweet wormwood plant (Artemisia annua), that seemed promising.
To help her find a way to extract the compound, she consulted the ancient Chinese medical literature. Now known as Artemisinin, this compound is highly effective at treating malaria (though some strains in Asia are resistant).
A 2010 study found that Artemisinin is estimated to reduce childhood deaths from Malaria by 30% more than quinine.
In a statement, the Nobel Assembly said, “Campbell, Ōmura and Tu have transformed the treatment of parasitic diseases. The global impact of their discoveries and the resulting benefit to mankind are immeasurable.”
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