Are Americans really riddled with parasites? No.
Parasite infections are uncommon in developed nations. But the wellness industry wants to profit by making you believe otherwise.
Please, do not use the ParaGuard “cleanse” or any other supplements claiming to rid you of GI parasites.
As is always the case with wellness pseudoscience, they premise claims on nuggets of truth. The truth here? Parasitic infections are a real thing.
The rest? Not supported by any factual information.
Are there places in the world that have serious public health concerns related to parasitic infections? Absolutely. But these aren’t the ones who are claiming they have parasites and need to cleanse themselves. In fact, these places are underserved when it comes to parasitic infections. I was reminded of this fact during my quarterly-ish catch-up with Dr. Peter Hotez.
If you don’t know, he has been focused on tropical and neglected infectious diseases for his entire career.
He was in Geneva at the World Health Organization (WHO) back in June to discuss his team’s recently developed Hookworm vaccine. Hookworms are parasites that can cause severe anemia, particularly in young children.
Their vaccine showed substantial efficacy in reducing morbidity and mortality, but the problem? Hookworm isn’t a concern for affluent and developed nations, so he’s struggling to figure out who will take up the mantle to manufacture and deploy this.
Anyway, I digress, but I wanted to use this to illustrate the fact that:
Developed nations do not have to contend with substantial cases of parasitic infections.
So why do so many relatively affluent people in the US believe they are riddled with parasites and need to take matters into their own hands with supplement-based “cleanses’?
Yep, you got it. The wellness industry is, once again, exploiting people’s health anxiety and low science literacy.
Parasites are a large category of different pathogenic organisms.
In the context of biomedical research, parasites are organisms that live on or inside a host organism and benefit at the host's expense. Technically, ALL pathogens are parasites, for the sake of this discussion we include:
endoparasites (those which live inside a host’s body): from single celled microscopic protozoans to large helminth worms
ectoparasites (those which live outside a host’s body): ticks, mites, fleas, lice, etc
Endoparasites can be further broken into single-celled protozoans and multicellular helminths:
Protozoans: single celled, eukaryotic organisms that use humans as reproduction vehicles.
Unlike viruses and bacteria, these organisms have a nucleus and are more structurally similar to animal cells (including humans). There are 4 major classes:
Sarcodina have pseudopods (fake feet) that they extend to “crawl” around. These are the amoebas.
Entamoeba histolytica causes amoebiasis (amoebic dysentery)
Naegleria fowleri causes primary amebic encephalitis (this is the one colloquially referred to as “brain-eating amoeba”
Acanthamoeba species cause acanthamoeba keratitis (an infection of the eye), Granulomatous Amebic Encephalitis (GAE), most often through contaminated contact lens use.
Mastigophora (flagellates) move using flagella: long whip-like appendages.
Giardia lamblia (also known as Giardia intestinalis or Giardia duodenalis) causes giardiasis.
Leishmania species cause Leishmaniasis
Trypanosoma brucei causes African trypanosomiasis/sleeping sickness.
Trypanosoma cruzi causes American trypanosomiasis, or Chagas disease.
Trichomonas vaginalis causes trichomoniasis which can cause vaginitis.
Ciliophora (ciliates) move using cilia: shorter hair-like appendages that allow them to “crawl”.
Balantidium coli causes balantidiasis, a type of dysentery.
Sporozoa (Apicomplexa) are non-motile in adult stages.
Plasmodium species cause malaria and are transmitted by Anopheles mosquitoes. These include P. falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi.
Toxoplasma gondii causes toxoplasmosis. This can be of concern to those who are immunocompromised, and can be spread by infected cat feces, which is why pregnant people should refrain from cleaning litter boxes.
Cryptosporidium species cause cryptosporidiosis.
Babesia species cause babesiosis. These are transmitted through the bite of infected Black-legged ticks, through blood transfusion, or vertically (mother to fetus during childbirth)
Helminths encompass a large group of parasitic worms that infect many different organisms.
There are (3) broad categories: nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes).
Nematodes are elongated, cylindrical worms with a smooth, unsegmented body that reproduce sexually and have distinct male and female forms. They have a full digestive system with separate mouth and anus.
Ascaris lumbricoides causes Ascariasis.
Trichuris trichiura causes whipworm (Trichuriasis).
Strongyloides stercoralis causes Strongyloidiasis
Ancylostoma duodenale and Necator americanus are your hookworms.
Onchocerca volvulus causes Onchocerciasis (River blindness)
Enterobius vermicularis causes Enterobiasis (Pinworm)
Cestodes (Tapeworms) have a long, flat, ribbon-like body composed of segments called proglottids. Each proglottid segment is hermaphroditic and contains male and female organs. These break off into individual segments and serve as a reproductive vessel, releasing eggs into the environment. Tapeworms absorb nutrients directly through the skin, and utilize their head (scolex) to attach to the intestinal wall of their host.
Taenia solium, the pork tapeworm, causes taeniasis and cysticercosis. Note: this is the worm that RFK Jr. reported he had, which I wrote about in more detail here.
Taenia saginata, the beef tapeworm, also causes taeniasis.
Diphyllobothrium latum, the fish tapeworm, causes Diphyllobothriasis.
Echinococcus granulosus, the dog tapeworm, causes cystic Echinococcosis.
Trematodes (flukes) have a flat, leaf-shaped body with a simple, unsegmented structure and have suckers on both ends (oral and ventral) they use to attach to tissues they have invaded. Flukes are hermaphroditic and often have multiple life stages.
Schistosoma species causes Schistosomiasis (Bilharzia)
Clonorchis sinensis cause Clonorchiasis (Chinese liver fluke infection)
Ectoparasites live outside your body and feed on blood and tissue fluids:
Lice including head lice, pubic lice (aka “crabs”), and body lice. These feed on blood of the host and can be potential vectors of certain diseases.
Ticks are arachnids that feed on blood. There are nearly 900 species globally: some of which can transmit disease to humans. Diseases of concern include Lyme disease, Rocky Mountain Spotted Fever, Babesiosis, Anaplasmosis, Tick-borne Relapsing Fever, and more.
Mites include scabies (Sarcoptes scabiei) and chiggers (larval Trombiculidae). These burrow into the skin or attach to the skin and feed on tissue fluids.
Flea species of concern are cat fleas and rat fleas. They feed on blood through biting and can be potential vectors of diseases like Bartonella henselae (cat scratch disease) and plague (Yersinia pestis)
Bed bugs feed on blood, but are not known to transmit additional pathogens.
Mosquitoes are biting blood-feeding flying insects which include many different species. Just like other ectoparasites, different species have the potential to carry and transmit pathogens to humans. Mosquitoes are the most prevalent disease-causing vectors, and depending on the species, are responsible for transmitting diseases such as: Zika virus, Dengue Fever, Chikungunya, Yellow Fever, West Nile virus, Malaria, Filariasis, Japanese Encephalitis, and Eastern Equine Encephalitis.
If it wasn’t clear, parasites are incredibly broad and diverse, and those that are of public health concern cause distinct potential illnesses.
Endoparasitic illnesses are relatively uncommon in developed nations.
We are going to focus on the endoparasites, because that is what these wellness products claim to treat.
If you look at the risk factors for protozoan and helminth parasites, there are common trends: lack of clean water, contaminated food and water sources, close proximity to animals that may be infected, poor food hygiene, etc. Many of these parasites are endemic to tropical and sub-tropical nations as well, partly because of the ecological factors that facilitate survival of them, but partly because those regions also tend to be the lower income developing nations.
The prevalence of parasitic infections in the United States is relatively low compared to other parts of the world.
Ones that we might encounter more frequently in the US?
Giardia (Giardiasis) is one of the most common parasites in the US, mostly from drinking untreated water. Even still, the prevalence is quite low: about 1.2 million cases per year, of a population roughly 333 million. That’s 0.36% of the population.
Fun fact: I had Giardia infections SEVERAL times as a child, because my childhood home abutted an expansive forest and I had a tendency to drink puddle and stream water if I was playing in the woods with my late brother and got thirsty. Silly kids.
But if you aren’t drinking puddle water or other untreated water sources, your risk is pretty low.
Toxoplasma is estimated to affect about 11% of the US population, but if you are not immunocompromised, you likely would never know. Toxoplasma parasites cause a mild or asymptomatic initial infection which presents as cold-like symptoms, but then parasites take up residence in your body in a dormant cyst form, where they pretty much exist for the rest of your life. Toxoplasma reactivation into the actively replicating form can be a concern for individuals with HIV/AIDS or other immunodeficiencies, but this is uncommon.
Another fun fact: I worked in a Toxoplasma gondii lab for a stint about 15 years ago. They are somewhat closely related to malaria parasites and are a useful model for studying disease pathologies in both illnesses.
Pinworm infections can be somewhat common among young children as they are transmitted through fecal-oral route and contaminated surfaces. Females migrate out of the anus to lay eggs on the skin in the perianal region which can spread very easily among clothing and bedding. Pinworms affect about 12% of the US population, with higher rates in shelters and communal living spaces with poor hygiene practices.
Tapeworm cases are quite rate in the US with less than 1,000 cases reported per year, mostly among people who consume contaminated and undercooked meat and fish. Typically, someone would consume the larvae in undercooked meat and the larvae mature into the adult form after ingestion. If you are privileged to have access to food supplies that are regulated for safety, tapeworm infections would be extremely uncommon.
Cryptosporidiosis infections lead to about 750,000 cases in the US every year (0.23% of the US population) with most infections occurring from contaminated recreation water (think community swimming pools).
The TL;DR?
Legitimate parasitic infections in the US are uncommon, particularly for those that would cause more serious illness. Groups at highest risk are recent immigrants, those who have traveled to tropical and sub-tropical areas, and those with insecure housing or living in underdeveloped areas in the US.
So why do so many relatively affluent Americans think they are filled with parasites?
Thank: the wellness industry! The GOOP gals are back at it, causing health anxiety and fear. This is a common trend in the unregulated wellness space: fabricate a medical condition and then claim to have the solution to cure it.
If you’ve been on social media at all, you’ve likely encountered videos or posts claiming that “over 80% of Americans are filled with secret parasites” right? Just to be clear: this is not supported by ANY credible evidence. But, it allows these influencers to sell unregulated dietary supplements and “cleanses” that are advertised to eliminate parasites and their associated toxins. (I explain WHY supplements are no longer regulated here, and it is entirely because of politicians).
One of the most common “parasite cleanses” is ParaGuard, an herbal supplement widely marketed that contains ingredients such as: wormwood, clove bud, pumpkin seed, garlic, oregano leaf, thyme, black walnut, peppermint leaf, gentian root, fennel seed.
Parasitic infections are treated with anti-parasitics, not unregulated herbal supplements.
There is no evidence that herbal dietary supplements like ParaGuard are doing anything to “treat” parasites. In fact, many have potential harms.
Parasite is a catch-all for many species of organisms, with different pathologies, different host:pathogen interactions, and diverse types of disease. As such, proper treatment requires an accurate diagnosis.
To treat parasitic infections, we use anti-parasitics: medications that target and interfere with transmission, replication, and survival of parasites. There are different anti-parasitics depending on which parasite pathogens you’re referring to. There is no “universal” parasite treatment. Beyond that, these “cleanses” claim to treat parasites of the GI tract, and wouldn’t even be relevant to a myriad of parasites, including Toxoplasma, Plasmodium, etc.
Malaria infection is treated with artemisinin-based combination therapy (ACT). Other medications like hydroxychloroquine, chloroquine, and quinine also exist, but in countries where malaria is endemic, certain Plasmodium species have evolved resistance to these older generation treatments.
Giardiasis is treated with an entirely different anti-parasitic, usually metronidazole. This medication has a different mechanism of action than anti-malarials, underscoring that even single-celled parasites differ from each other.
If you’re talking multi-cellular helminths like pinworms, those are treated with different anti-parasitics, most often mebendazole or albendazole. Mebendazole interferes with the formation of proteins required for digestive tract function.
Tapeworms are ALSO be treated differently. First line treatment for Taenia species is prazinquantel, a medication which interferes with muscle contraction of parasitic worms, causing paralysis and death.
So why did these herbal “parasite cleanses” gain traction?
Well, like usual, supplement manufacturers exaggerate the implications of the ingredients. For example, limited in vitro and animal data exist that suggest some of the ingredients in ParaGuard have “anti parasitic” effects, but these studies routinely utilize excessively high dosages, dosage which would cause harm in people. Unfortunately, there is no clinical evidence they offer a benefit in humans.
You can do anything to cells growing on a piece of plastic. That doesn’t mean that’s what happens in a human.
There are serious risks associated with ParaGuard and other “parasite cleanses”
Herbal supplements are common causes of medical emergencies due to liver and kidney toxicity. Just because something is natural does not mean it is benign: that is the the appeal to nature fallacy (I wrote about here).
Wormwood can cause serious neurological issues including seizures as well as as liver and kidney toxicity. Adverse effects are a result of many chemicals found in the plant, including thujone (also found in absinthe), a compound with a 50% lethal dose estimated at 45 mg/kg body weight.
Wormwood is a particularly useful example, because a substance used for legitimate parasitic infections, artemisinin, can be isolated from wormwood. However, in contrast to wormwood supplements, artemisinin has clinical evidence, and is regulated for purity, safety, and efficacy. And because of that regulation, it has a well-documented safety profile, plus artemisinin has much lower toxicity (4,000 mg/kg body weight) and is dispensed and prescribed by trained medical professionals.
Other ingredients found in these products have similar themes. Remember, toxicity depends on the dosage, even for “natural substances” and many of these ingredients can be toxic at relatively low dosages. In addition to not having demonstrated efficacy for parasite infections, clove oil can pose a risk for liver damage, respiratory issues, and allergic reactions.
The main ingredient in clove oil, eugenol, can have dangerous drug interactions:
Blood thinners such as warfarin (Coumadin), aspirin, clopidogrel (Plavix)
NSAIDS such as ibpuprofen (Advil), naproxen (Aleve)
Medications that are metabolized through liver enzymes CYP2E1, CYP2D6, and CYP3A4, including certain antidepressants, antipsychotics, and statins
Blood glucose medications such as insulin, metformin, and other oral hypoglycemics.
Other medications metabolized by the liver including acetaminophen (Tylenol), antiepileptics, and other antidepressants.
Sedatives such as benzodiazepines, barbiturates, and alcohol.
I could continue, but I think you get the idea. Other ingredients like pumpkin seed, thyme, black walnut hull, gentian root can cause gastrointestinal upset and issues and aggravate medical conditions such as stomach ulcers, heartburn, and GERD. Others like oregano can also interact with some of the same medications listed above for clove oil. Several of these common ingredients do not have safety data.
But I’ve seen the videos: people are pooping out things they say are parasites!
Unfortunately, that’s not true either. In addition to these supplements not having evidence to support their use and the fact that parasitic infections, particularly worms, are uncommon in the US, these substances can be severely irritating to the mucosal lining of your intestinal tract.
Frequently, these videos contain “stringy material” that people claim are killed parasites. But in reality, they are a combination of mucus, undigested food, ingredients from the supplement itself (which can change in texture in your GI tract), and, most horrifyingly, sloughed off cells from your intestines.
These objects people notice in their stool are not parasites and should be a warning sign of harm to their GI system. While mucus and sloughed intestinal cells are always found in stool, increased production of mucus is a sign of irritation and tissue damage. Other ingredients can have laxative properties, which means you’re artificially increasing the rate of food traversing your GI tract, leading to potential malnutrition and dehydration issues as well.
Please: do not fall prey to these dangerous wellness trends and products. There is not evidence to support these types of herbal supplements and they are not benign: they can cause serious harm to your health. If you encounter someone recommending them, or worse, selling them, that should be a red flag that the person does not understand science and they are trying to exploit people for profit. You should ALWAYS seek credible medical care if you have legitimate reason to believe you may have a parasitic infection.
Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, propagation of pseudoscience by prominent public “personalities”, it’s needed now more than ever.
Stay skeptical,
Andrea
“ImmunoLogic” is written by Dr. Andrea Love, PhD - immunologist and microbiologist. She works full-time in life sciences biotech and has had a lifelong passion for closing the science literacy gap and combating pseudoscience and health misinformation as far back as her childhood. This newsletter and her science communication on her social media pages are born from that passion. Follow on Instagram, Threads, Twitter, and Facebook, or support the newsletter by subscribing below: