How did we get to the point where people want to treat Covid by squeezing a fat tube of horse wormer into their mouths? Mirjam Guesgen explains.

“You are not a horse. You are not a cow. Seriously, y’all. Stop it.” That’s a real tweet from the US Food and Drug Administration (FDA). They’ve seen the need to remind people what species they are after hordes of North Americans turned to a horse worming drug in an attempt to treat Covid-19.

There are signs that the latest Covid-19 “wonder drug” has been pushed by some fringe groups in New Zealand too. That’s led to warnings from the Ministry of Health and prominent veterinarians. The drug in question is ivermectin. It’s a parasite-killing drug found in cow and horse worming pastes. Similar drugs make up sheep drenches. Think of it as the hydroxychloroquine of 2021. 

It has been touted as a cure by the likes of Joe Rogan and others sceptical of vaccination. A new YouGov poll for the Economist reveals that a third of American conservatives believe it is either “possibly” or “very” effective as a Covid-19 treatment. Its popularity has led to farm supply stores across the States running short or asking people to show a picture of their horse – to prove it’s for the animal, not them – before purchasing. Its popularity has led to a stable full of memes.

It should go without saying, but taking medication designed for livestock is dangerous. The FDA has received multiple reports of people needing to be hospitalised after ingesting the horse paste. Taking the wrong dose can lead to vomiting, low blood pressure, allergic reactions, seizures, coma and even death, the agency warns. In recent days a Sydney woman was hospitalised after self-medicating with ivermectin.

How did we get to the point where people want to squeeze a fat tube of horse wormer into their mouths? 

Ivermectin is used in human medicine to treat things like an intestinal infection with roundworm or scabies. At a time when researchers were looking at whether existing drugs could be used to treat Covid-19, it popped up as a potential solution. Then a scientific study from 2020 showed that ivermectin could curb the SARS-CoV-2 virus’s ability to replicate in cells in a petri dish. In fact, it seemed to work against a whole host of viruses in the lab.

This isn’t groundbreaking or convincing, says Kurt Krause, an infectious diseases physician and professor of biochemistry at the University of Otago. “There’s no shortage of things that kill things in cell culture,” he told The Spinoff. 

Other studies emerged, outlining the potential way the drug prevented the viruses from replicating and a “very crude” study (according to Krause) that showed ivermectin could bind to the receptors on the coronavirus. “Honestly it was just an exercise you could set up over dinner and run it. It has no connection to reality whatsoever. I was completely amazed that it ended up being discussed,” he says.

Then a few observational studies with small sample sizes sprung up demonstrating ivermectin’s potential. “Because you got better after taking a drug you assume you got better because you took the drug. The problem is this is a post hoc ergo propter [after this, therefore because of this] argument.” 

Essentially, just because something happens after something else, doesn’t mean the first thing caused the second.

There have been several, mostly small clinical trials done on the human version of ivermectin. However the consensus, according to WHO, the NIH and independent healthcare review journal the Cochrane Library, is that evidence for using ivermectin to treat Covid-19 is weak and poor quality. That means it’s not currently possible to say whether Ivermectin is or isn’t beneficial against Covid-19 in people. WHO recommends that the drug only be used in clinical trials for now.

But after a few rowdy speeches in front of congress, the drug caught on like wildfire, says Krause.

It’s still a mystery though, how scant evidence from human trials led to people taking a paste intended for animals. Now, with poison control centres in the US ringing off the hook, agencies such as the Centers for Disease Control and Prevention, FDA, the UK’s National Institutes of Health and New Zealand’s own Ministry of Health are urging people not to take the drug – neither the human nor the animal version. 

The FDA especially warns against people taking drugs intended for animal use because they haven’t been tested for their safety and efficacy in people and because the animal versions could make the illness worse and lead to life-threatening health complications. Plus it means the drugs aren’t available for the animals who need them. It’s meant for livestock.

The FDA especially warns against people taking drugs intended for animal use because they haven’t been tested for their safety and efficacy in people and because the animal versions could make the illness worse and lead to life-threatening health complications. On top of that it means the drugs aren’t available for the animals who need them.

Virbac, the veterinary pharmaceutical company that makes ivermectin-based horse wormers in New Zealand, says it “has not experienced any unusual or unforeseen increase in demand for products containing ivermectin”. However, some online pharmacies are out of stock of the human version of the drug due to “nationwide shortages”. 

Says Krause: “The same people who won’t take a vaccine that has been given to billions to people around the world – an extraordinarily safe vaccine – are willing to take a cow medicine and a cow dose, but their argument against the vaccine is that it’s not safe?”

This post was updated to include clinical trial information.