The claim: Ivermectin won Nobel Prize for its role in treating human disease  

Debate over potential COVID-19 treatments has been a constantly evolving saga over the last year, with drugs like hydroxychloroquine and recently ivermectin touted by many despite a lack of convincing scientific evidence.  

Demand for ivermectin reached a fever pitch as prescriptions for the anti-parasitic agent shot up by 2,400% by the middle of August compared to the weekly average prior to the pandemic, according to the Centers for the Disease Control and Prevention. Ivermectin poisoning calls have also increased by 163%, according to data collected by the American Association of Poison Control Centers. 

Despite this, some social media users continue to support the drug, citing a high-profile award in an attempt to legitimize its controversial use against the virus.

"If you just got finessed into calling the medicine that won the 2015 Nobel Prize for its role in treating human disease 'horse de-wormer', then you need to sit the next couple of plays out," reads a graphic shared in a Sept. 6 Facebook post. 

The graphic has been shared widely on the social media platform, and it was recently echoed by popular podcaster and UFC commentator Joe Rogan – who reportedly used ivermectin when being treated for COVID-19. He raised the issue during an episode of the "Joe Rogan Experience," a clip of which was shared in a Sept. 8 Instagram post.  

The posts have collected thousands of interactions across Facebook and Instagram within the last few weeks, according to CrowdTangle, a social media insights tool.

Fact check: Pfizer, Moderna and Johnson & Johnson COVID-19 vaccines all passed animal testing

While a precursor of ivermectin, known as avermectin, did win its two discoverers the 2015 Nobel Prize in Physiology and Medicine, it was related to treatment of parasites. It wasn't related to anything like a coronavirus.

USA TODAY has reached out to the Facebook and Instagram users, and Joe Rogan, for comment. 

From golf course to veterinary drug

Avermectin's origin story calls to mind the famous case of penicillin's discovery, when it was fortuitously extracted from a mold left growing in a lab. Avermectin was extracted from a soil-dwelling bacteria growing outside a Japanese golf course southwest of Tokyo. 

The bacteria, later christened Streptomyces avermectinius, was cultured in the 1970s by biochemist Satoshi Omura, who had been collecting soil samples all over Japan while hunting for new medicinal compounds.

The sample would later be sent to Merck Research Laboratories, which struck a royalties agreement with Omura's Kitasato Institute. The pharmaceutical giant, at the time, was particularly interested in creating therapeutics for veterinary use. 

Fact check: There is no evidence 45,000 people died from vaccine-related complications

In the late 1970s, a Merck researcher, parasitologist William Campbell, found that when mice infected with intestinal roundworms were given the bacteria from Omura's soil sample, the parasites were effectively wiped out. 

The key ingredient stifling the parasites, Campbell's team discovered, was a chemical they named avermectin, which turned out to be a mixture of eight closely related compounds. The most effective of these compounds, Avermectin B1 (made of a pair of molecules), was further tweaked and modified to overpower its parasitic targets yet be safe enough for the animals treated. In 1981, after clinical trials in animals, Merck commercialized the Avermectin B1 derivative, ivermectin, for veterinary use. 

Potential for human use 

By the 1980s, ivermectin was the top-selling veterinary drug in the world. This is also when potential human applications emerged. 

Onchocerciasis is a parasitic disease transmitted to humans through the bites of infected blackflies. The parasite, commonly found in tropical climates of Africa and South America, infests by migrating into its host's eye, causing inflammation, bleeding and other symptoms resulting in blindness.

Campbell's team at Merck had discovered ivermectin was effective against a close relative of that parasite in horses but doesn't cause disease. This discovery encouraged Merck to test ivermectin in treating river blindness, which, in 1981, led to the first clinical trial of human volunteers in Senegal.

The success of these, and many other, human trials over the next several years, led to ivermectin being distributed in 1988 to countries affected by river blindness and another parasitic disease called lymphatic filariasis, which is caused by microscopic worms that invade the human lymph system.

The FDA approved ivermectin for human use as an antiparasitic drug in 1996 for treatment of river blindness and strongyloidiasis, another parasitic infection that mostly infects animals but humans as well.

In 2015, Campbell and Omura were awarded the Nobel Prize in Physiology or Medicine for the drug's application in roundworms. The Nobel announcement praised the duo – and another recipient awarded for a malaria treatment – for developing "therapies that have revolutionized the treatment of some of the most devastating parasitic diseases."

But ivermectin is not recommended for any other disease

Winning a Nobel Prize does not legitimize ivermectin's use for anything but parasitic infections, however. Despite the demand for ivermectin during the pandemic, there is no significant evidence pointing to its effectiveness against viruses like COVID-19.

"The reason for the interest in ivermectin is that studies in the lab have shown it can block viruses from multiplying in experimental settings – i.e. in a petri dish – and so people hoped this would mean it could help treat COVID-19 in people too," Dr. Denise McCulloch, an infectious disease specialist with the University of Washington's School of Medicine, said in an email to USA TODAY. "Unfortunately, the few high-quality studies that have been done to date do not demonstrate a beneficial effect of ivermectin when it is used in people with COVID-19."

The FDA has also cautioned against the use of the antiparasitic drug, stating the agency "has not authorized or approved ivermectin for use in preventing or treating COVID-19 in humans or animals."

The CDC warns its use is particularly dangerous since some people are purchasing it without a prescription and ingesting large quantities of the more concentrated dosages intended for horses and other large animals.

Our rating: Missing context

Based on our research, we rate the claim ivermectin won a Nobel Prize for its role in treating human disease MISSING CONTEXT, because without additional information it could be misleading. The discovery of ivermectin's precursor, called avermectin, helped its co-discoverers win the 2015 Nobel Prize in Physiology or Medicine for its use in treating parasites. This does not mean ivermectin works against viruses like COVID-19, as there are no significant studies to date pointing to its effectiveness. 

Our fact-check sources:

Contributing: Daniel Funke, Ella Lee

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This article originally appeared on USA TODAY: Fact check: Precursor to ivermectin did win Nobel Prize, but it's not a proven COVID-19 treatment