On Our Way to Eradicating Parasitic Diseases
by Maggie Brown
The Nobel Prize – the most prestigious recognition for academic achievement. This year, we delve into the world of microbes and parasites that still plague many societies today – malaria, river blindness, filariasis and various other diseases.
The winners of the 2015 Nobel Prize in Physiology or Medicine was awarded to scientists responsible for developing a new class of anti-parasitic drugs. Half of the $960,000 award went to Dr. Youyou Tu of China for her discovery of Artemisinin, a drug that has become a crucial part of standard anti-malarial treatments. The other half of the award was shared by Dr. William Campbell of New Jersey and Dr. Satoshi Omura of Japan for their collaboration in developing Ivermectin, a drug used to cure diseases caused by parasitic roundworms.
Tu began her work in 1967 when Mao Tse-tung initiated a secret research project, whose code name was “523,” during the height of the Vietnam War. The project was launched across 50 laboratories and 500 scientists in response to malaria claiming the lives of more North Vietnamese soldiers than US soldiers. Tu and her team believed they could potentially design a drug by analyzing numerous ancient Chinese medicinal texts, looking for remedies that have not been used before. After testing many of the recipes in these manuscripts, Tu and colleagues eventually found a promising manuscript dating back to 340 A.D., called “Emergency Prescriptions Kept Up One’s Sleeve.”
The manuscript contained a recipe for the preparation of the herb Artemisia annua - commonly known as sweet wormwood. In the initial tests on 21 human subjects, the active ingredient Artemisinin was observed to wipe out the deadliest form of malaria caused by the parasite Plasmodium falciparum. In addition, the Artemisinin ingredient was also found to eradicate the most common form of malaria caused by the parasite, Plasmodium vivax.
Tu’s discovery of a new treatment for malaria occurred at a critical time in 1967, when the P. falciparum and P. vivax parasites were becoming resistant to chloroquine and quinine –drugs that were the only treatments available for malaria at the time. With the introduction of Artemisinin into local hospitals, the mortality rate of those suffering from malaria has been reduced by over 20 percent in adults and over 30 percent in children.
Beyond the contributions of Tu, two other scientists were able to successfully harness the medicinal capabilities of natural substances.
Microbiologist Satoshi Omura, a professor at Kitasato University in Tokyo, is known around his lab for carrying a plastic bag with him at all times to collect soil samples. He uses the soil to grow bacteria that produce their own anti-microbial compounds. One sample in particular, taken from a local golf course, contained the bacterium Streptomyces avermitilis. Omura was able to isolate this bacterium and collaborated with his colleague, Dr. William Campbell, who found that purifying the Streptomyces avermitilis cultures resulted in Avermectin, a substance that proved extremely effective against parasites in farm and domestic animals.
Further chemical modification of Avermectin produced Ivermectin, which kills parasitic roundworms in infected humans. When tested in human studies, Ivermectin was observed to nearly eradicate a disease commonly known as river blindness, caused by chronic inflammation of the cornea. In addition, this drug has profoundly decreased the number of cases of filariasis, a disease that can cause swelling of the lymph system in the legs and lower body, better known as elephantiasis. Ivermectin has shown promise for being effective against many other parasitic diseases as well, but as of now, it is effectively preventing severe swelling and disability that often leads to people being shunned by their communities.
Instead of patenting Ivermectin and making a hefty profit, the scientists have chosen to give the drug to those who need it free of charge. Deputy director of the Liverpool School of Tropical Medicine Steve Ward commented on Campbell and Omura’s discovery, stating that “Elephantiasis and river blindness blight the lives of millions of the poorest people on the planet, and Ivermectin is having a genuine effect on reducing the burden of disease to the point that we can think about getting rid of them for good.” With the cost of Ivermectin not being a limiting factor, the possibility of eradicating parasitic diseases “for good’ is now within reach.
The vast majority of those who suffer from parasitic diseases live in some of the poorest regions of the world and cannot afford simple medical treatments. While 100 million people in these regions currently suffer from filariasis, over 3.4 billion people are at risk of contracting malaria and an overwhelming 450,000 people—mostly children—die from it each year.
Making these drugs widely accessible and therefore relatively inexpensive or even free of charge is crucial to the future of millions who are at risk. This new class of anti-parasitic drugs has fundamentally changed the treatment of diseases caused by parasites, saving and improving countless lives. All in all, the Nobel Prize was one truly deserved by the three phenomenal scientists.