Ivermectin can help patients with covid-19 – but only those with worms

“THIS COME, ” cried Andrew Hill, the lead author of an unreviewed meta-analysis looking at whether ivermectin, an antiparasitic drug, was helpful in treating covid-19. “Get ready, get supplies, get ready to approve it,” advised Dr Hill, a visiting fellow at the University of Liverpool.

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Such lobbying proved far too optimistic. One of the articles cited in the report was withdrawn because its data was fraudulent; the report itself was withdrawn as well. Two of the largest and most rigorous randomized controlled trials also found no evidence that the drug was helpful. As a result, ivermectin has never become part of the standard of care for covid-19.

However, activists of ivermectin insist that there is solid science proving the effectiveness of the drug. One well-documented website lists and links to 65 different articles on the subject, many of which, on the surface, seem to support this claim. Could these many studies all be wrong? Recent analysis of Avi Bitterman, a dermatologist in New York City, and Scott Alexander, a prominent blogger, suggest the answer is nuanced. Ivermectin is likely to help one subset of patients with covid-19: those who are also infected by the worms it was destined to fight.

Wading through the articles, whose methodologies seemed solid, Dr. Bitterman noted that the studies that looked best for ivermectin tended to accumulate in regions with high rates of strongyloid, parasitic worm infections. Common in much of Africa, Asia, and Latin America, strongyloides can cause, among other things, diarrhea, fatigue, and weight loss. However, they pose a more serious threat only if their numbers grow out of control. Such a “hyper-infection,” which is often fatal, becomes much more likely if a patient receives corticosteroids, both of which suppress the immune system and appear to make female worms more fertile. And dexamethasone, a corticosteroid, is now a standard treatment for severe covid-19, as it prevents the immune system from speeding up and attacking the body’s own cells.

Building on observations by David Boulware, a professor of medicine at the University of Minnesota, Dr. Bitterman concluded that strongyloides may be responsible for the conflicting results of studies on the effectiveness of ivermectin as a treatment for covid-19. In tests done in countries where parasites are common, many people could have both covid-19 and strongyloid infections. Covid-19 may have already weakened their bodies ’defenses against the worms; treating the coronavirus with corticosteroids would let the parasites go wild.

In the groups that received ivermectin during testing, the drug would keep strongyloids under control. But patients in control groups would be left to the mercy of the worms. This would seem as if ivermectin would prevent deaths caused only by covid-19, when in fact it prevented those caused by the parasites or by a combination of the two infections. This mechanism would explain why most studies done in places where strongyloides are rare have shown no benefit from taking ivermectin. “Ivermectin does not treat covid,” Dr. Bitterman wrote. “It treats parasites (shocks) that kill people when they get steroids that treat covid.” He concluded that “taking strongyloides endemic populations, putting them in a control group with corticosteroids is a death sentence”.

In July 2020 a group of doctors quarreled in the Journal of the American Medical Association that it was “reasonable to consider possible treatment with ivermectin for moderate to high-risk patients not previously tested or treated for strongyloids,” and said the risk of worm infection in patients with covid-19 should be based on factors such as country of origin. The World Health Organization also recommends ivermectin in this context.However, most people in rich western countries like America – where demand for ivermectin, driven by social media advocates, is so high that some people have used the horse version of the drug – does not match this description.At least when treating patients who have never been in countries with widespread strongyloides, the evidence suggests that leading physicians in such places are right to avoid prescribing ivermectin.

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