• Health

No evidence that hydroxychloroquine and ivermectin cure cancer; cancer and multiple sclerosis aren’t caused solely by parasites, contrary to claim by orthopedic surgeon

Posted on:  2023-05-12

Key takeaway

Various infectious agents, including certain viruses and parasites, can increase a person’s risk of developing specific cancers. Cells can become cancerous in various ways, such as when the infectious agent directly damages DNA, causing mutations, or indirectly by causing chronic inflammation. Multiple sclerosis (MS) is a neurological disorder thought to be autoimmune in nature. To date, established risk factors for MS include genes and infection. However, parasites aren’t among these risk factors.

Reviewed content


Cancer and multiple sclerosis are caused by parasites; hydroxychloroquine and ivermectin can cure cancer

Source: After House with Dr. Sigoloff, After Hours with Dr. Sigoloff, Lee Merritt, 2022-12-05

Verdict detail

Incorrect: Certain types of cancer are associated with chronic infection by specific parasites, but there are many different risk factors for cancer. Cancer isn’t solely caused by parasites. The exact cause of multiple sclerosis is unknown. Risk factors for it include a genetic predisposition and infection by the Epstein-Barr virus, but there’s no established causal link with parasites.
Unsupported: There are some preclinical studies in cell cultures and animals about the effect of hydroxychloroquine or ivermectin on cancer cells. However, neither of the two have been shown in clinical trials to effectively treat cancer in people.

Full Claim

“What if cancer is really parasites???”; “cancer is parasites”; “Dr. Macdonald did […] a series of autopsies on multiple sclerosis patients and a 100% of them had parasites in the brain and spinal cord”; Taking antiparasitic drugs will get rid of “the nano-synthetic parasite” in COVID-19 vaccines and prevent cancer and other ill effects from the COVID-19 vaccines


A Facebook video posted on 5 May 2023 claimed that parasites cause cancer and multiple sclerosis, receiving more than 130,000 views. The video is an excerpt from a 5 December 2022 episode of the podcast “After Hours with Dr. Sigoloff”, during which orthopedic surgeon Lee Merritt made the claim. The podcast is hosted by Samuel Sigoloff, a U.S. Army physician and one of a trio of doctors who incorrectly claimed the Defense Medical Epidemiology Database showed a massive spike in health problems among army personnel due to COVID-19 vaccination.

Merritt is a member of the fringe medical group America’s Frontline Doctors. She previously made false claims about COVID-19 and COVID-19 vaccines; Health Feedback explained why these claims were inaccurate in a previous review.

Merritt made the claim on Sigoloff’s podcast in the context of a broader discussion about the COVID-19 pandemic, and is simply one in a long list of false claims. Merritt alleged, among several things, that 5G was responsible for COVID-19 (it’s not); that graphene oxide is present in COVID-19 vaccines (it’s not); that COVID-19 vaccines dramatically increase the risk of negative pregnancy outcomes (they don’t).

This review will focus on Merritt’s claims that cancer and multiple sclerosis are caused by parasites, that the COVID-19 vaccines contain parasites, and that hydroxychloroquine and ivermectin can prevent cancer by removing the “nano-synthetic parasite” in the vaccines.

Cancer can be caused by many different factors, including infection; not all cancers are due to parasites

Cancer occurs due to mutations in cells that result in uncontrolled growth and proliferation. Infection with certain biological agents can increase one’s risk of cancer in various ways. One well-known example is the human papillomavirus (HPV), which can directly damage DNA, producing mutations. HPV can cause cervical, oropharyngeal, and anal cancer.

Others are the hepatitis B and C viruses. Chronic infection with these viruses greatly increases a person’s chances of developing liver cancer, as both viruses can directly or indirectly make cancerous transformation more likely, for example by making mutations more likely or by interfering with the cell cycle, which controls cell proliferation[1,2].

Some of these processes also occur during infection with a handful of parasites. The International Agency for Research on Cancer (IARC), part of the World Health Organization, recognizes chronic infection with any of these three worms, Schistosoma haematobium, Opistorchus viverrini, and Clonorchis sinensis as cancer-causing (Group 1 carcinogens). S. haematobium is associated with bladder cancer[3], while both O. viverrini and C. sinensis are associated with cholangiocarcinoma (a cancer of the bile duct).

According to an IARC monograph published in 2012, scientific evidence so far points to chronic inflammation as the driving force behind cancerous transformation in cells. This occurs in various ways, such as through the secretion of chemical signals that promote tumor growth and survival, as well as the production of free radicals that damage DNA.

Health Feedback also reached out to the U.S. National Cancer Institute (NCI) regarding this claim. In an email, the NCI stated that while certain parasites can cause cancer, “there are many other risk factors that have been identified, and that the presence of a risk factor is not a guarantee that cancer will develop”.

In summary, while chronic infection with certain parasites can lead to cancer, Merritt’s assertion that “cancer is parasites” falls wide of the mark. Many different risk factors increase one’s likelihood of developing cancer, such as smoking, obesity, as well as alcohol. Cancer isn’t caused solely by parasites, nor is it composed of parasites, as Merritt’s claim might lead one to believe.

COVID-19 vaccines don’t contain parasites; neither hydroxychloroquine nor ivermectin are proven cancer treatments

Merritt also claimed that antiparasitic drugs like hydroxychloroquine and ivermectin can be used to get rid of the “nano-synthetic parasite” in the COVID-19 vaccines and could treat cancer.

Misinformation about the contents of the COVID-19 vaccines has been rife throughout the pandemic, eliciting emotional responses of fear and disgust in people and playing on the desire of some to remain “pure”. The end result of this is to discourage people from vaccination.

The alleged contents of the vaccines have ranged from graphene oxide, microchips, and parasites, despite the absence of evidence for these claims. Images that allegedly show parasites in the COVID-19 vaccines have been of unknown provenance, are of poor quality and unidentifiable as a known parasite, or simply misrepresent old footage of completely different living things and even non-living things.

Jérôme Martin, the co-founder of the Drug Policy Transparency Observatory in France (l’Observatoire de la transparence dans les politiques du médicament), told France 24 Observers that it would be impossible for parasites, or any other living creature, to exist in the COVID-19 vaccine. “The water and other liquids within the vaccine are purified under strict conditions, which prevents any parasites or other living organism within the vaccine,” he said.

There’s insufficient evidence for the claim that antiparasitic drugs like hydroxychloroquine and ivermectin—also touted as COVID-19 cures although the evidence doesn’t support this—are effective at treating cancer in people.

While hydroxychloroquine and ivermectin have been tested in some preclinical studies to determine their effect on cancer cells, at the moment, these studies don’t provide the necessary evidence to conclude that either drug effectively treats cancer in people.

The results of these studies are also a mixed bag. Some reported that chloroquine, a drug that is highly similar to hydroxychloroquine, could slow down tumor growth in mice[4,5], but others observed accelerated tumor growth instead[6,7].

Similarly, studies about the effect of ivermectin on cancer so far are limited to preclinical studies in cell cultures (cells growing in dishes in the laboratory). Susanne Arnold, an associate director for clinical translation at the Markey Cancer Center in Kentucky, told The Associated Press that such studies aren’t enough to prove the drug works on cancer in people, adding “I know of no reports of clinical trials that yielded successful results in humans with cancer”.

Peter Lee, the chair of the department of immunooncology at City of Hope, who conducts research into ivermectin’s effect on breast cancer in combination with other drugs, told AFP that “There’s certainly truth to ivermectin being able to kill cancer cells,” but that this needs to be combined with “immune activation”, and “we’re really in the process of figuring that out now”.

He also highlighted that the drug combinations only work with certain doses taken at specific times: “Simply saying somebody’s going to take some ivermectin that they got from a veterinarian office—that’s not gonna fly whatsoever.”

The NCI stated that ivermectin is approved by the U.S. Food and Drug Administration for treating certain parasitic infections, based on findings in clinical trials. In contrast, it was “not aware of any similar clinical trials” that proved ivermectin is effective against any cancer. Specifically:

ClinicalTrials.gov, a website of the U.S. National Library of Medicine (NLM), lists 214 trials—ongoing, not yet enrolling, completed, and terminated—for ivermectin.  Of these, only four are studying the drug’s effects against cancer, in combination with other drugs.  There is one new trial, not yet recruiting, studying ivermectin and pembrolizumab for the treatment of metastatic triple-negative breast cancer.

No reliable evidence that multiple sclerosis is caused by parasites

To support her claim that multiple sclerosis (MS) is caused by parasites, Merritt cited the work of Alan Macdonald, a pathologist in Florida who claimed that “multiple sclerosis is a parasitosis”, purportedly based on his examination of tissue from MS patients.

However, there’s no indication that this work was peer-reviewed or published in scientific journals, nor is there reliable evidence elsewhere showing that multiple sclerosis is due to parasitic infection. Macdonald also promotes the concept of chronic Lyme disease, which asserts that persistent infection with the causative agent of Lyme disease, typically the bacterium Borrelia burgdorferi, is the cause for a wide variety of medically unexplained symptoms.

But there’s a lack of evidence for this. The Infectious Diseases Society of America stated that the term chronic Lyme “has been applied to a highly heterogeneous patient population, including patients with prolonged and unexplained symptoms who lack objective features of Lyme disease, many of whom prove to have alternative medical diagnoses”.

Multiple sclerosis is a chronic neurological disorder that is thought to be due to the body’s immune system mistakenly attacking myelin. Myelin is a fatty substance that coats and insulates neurons (nerve cells), permitting electrical signals to travel to and from the brain. In MS, myelin is destroyed by the immune system, which interferes with the transmission of electrical signals.

Exactly what causes MS is still not known, but there are several factors associated with a higher MS risk, including a genetic predisposition as well as infection. One of the infectious agents most strongly linked to MS is the Epstein-Barr virus, which also causes infectious mononucleosis (also called “mono”).

Interestingly, some research suggests that infection by certain parasites reduces the likelihood of developing MS or reduces relapses, contrary to Merritt and Macdonald’s claim. The Multiple Sclerosis Association of America (MSAA) stated that “Parasites are a possible risk-reduction factor in the development of MS”:

The parasites in this instance are ‘helminths,’ which refer to a wide variety of worms. Some are thought to be harmless, and many people had pinworms as children. Research has found that parasites can modulate the immune system and dampen its responses. People who have parasites are less likely to be diagnosed with MS.

However, the MSAA also cautioned that certain parasites could make MS worse. According to the U.K. non-profit Multiple Sclerosis Trust, studies about the effects of parasites on MS are small and have produced mixed results. Therefore, more research still needs to be done in this area to better understand the relationship between MS risk and parasitic infection.

UPDATE (15 May 2023):

We added statements from the U.S. National Cancer Institute in the ninth and twentieth paragraph.


Science Feedback is a non-partisan, non-profit organization dedicated to science education. Our reviews are crowdsourced directly from a community of scientists with relevant expertise. We strive to explain whether and why information is or is not consistent with the science and to help readers know which news to trust.
Please get in touch if you have any comment or think there is an important claim or article that would need to be reviewed.

Published on:


Related Articles