Helminthic therapy safety
Considering benefits and risks
Every practice - even the healthiest - has risks. For example, eating healthy food carries the risk of choking, and exercise may result in injury. But the risks of eating a healthy diet and exercising are clearly more than offset by the reduction in the risk of heart disease, cancers, and a very wide range of inflammatory diseases that are associated with these practices. Modern medicine also considers the risks of any drug alongside the risks of not taking the drug. By the same token, when considering the risks of helminthic therapy, it is important to weigh those against the risks of not engaging in this practice.
Current scientific understanding of the immune system’s development and function indicates that routine exposure to helminths is probably necessary for proper immune function. In this view, the loss of helminths in Western society (known as loss of “old friends”, biome depletion, or biota alteration) as a result of necessary sanitation practices has left the ecosystems of our bodies highly susceptible to inflammatory disease. Consistent with this view, socio-medical studies indicate that self-treatment with helminths is effective for many people, probably even most people, in terms of alleviating inflammatory-related diseases. These findings are supported by a few clinical trials and numerous studies in animal models.
Many of the risks to human health from biota alteration are readily apparent, with a wide range of allergic and autoimmune conditions attributed to biota alteration. Further, diseases not currently confirmed to be associated with biota alteration, including Parkinson’s disease and a variety of other cognitive problems, may be associated with biota alteration. As described by Parker, “it seems highly likely that self-treatment with helminths, despite its unknown risks, varied and changing practices, and poorly defined outcomes, is more beneficial than harmful to the average practitioner.” Parker further argues that physicians violate the principle of primum non nocere (first, do no harm) when they arbitrarily discourage self-treatment with helminths.
In weighing the risks and benefits of helminthic therapy, each individual must keep in mind that to remain helminth-free is a choice to maintain the body in a state of biota alteration which, based on the modern science described above, is pro-inflammatory and thus at risk.
Known and possible contraindications for the use of helminthic therapy
- Patients with a serious, life-threatening infection such as HIV/AIDS, or who are severely immunosuppressed. However, this does not include those who are taking immunosuppressive medications to treat autoimmune, inflammatory or allergic diseases. For more on this see Combining helminthic therapy with drug treatments.
- Patients with severe intestinal strictures. Hookworm larvae can temporarily increase inflammation in the small intestine in the initial stages of colonisation and this might close a very narrow stricture, especially if the guidance on the Hookworm dosing and response page is not followed carefully.
- Patients whose cardiac arteries are severely narrowed due to atherosclerosis. The temporary increase in inflammation following the initial introduction of helminths, especially hookworms, may exacerbate this condition, possibly occluding an artery and triggering a heart attack.
- Patients with bleeding or blood clotting disorders are advised to monitor their clotting times when hosting hookworms. For more details see Can hookworms make their hosts' blood too thin?, below.
- Patients with acute anaemia/anemia. Hookworms have a potential to slightly lower hemoglobin levels, so it may be advisable to correct any existing anaemia before proceeding with the use of this species. For more details, see the Helminthic therapy and nutritional deficiencies page.
- Patients with a latent viral infection such as herpes or tuberculosis may experience a temporary exacerbation of their condition following inoculation. For more details, see Helminthic therapy and viral infections.
- Patients who have had a diagnosis of cancer. Helminth providers may be reluctant to supply anyone in this situation, even if the cancer is in remission, although they may be willing to supply someone with a relatively benign cancer or one that is very easy to treat. See: Helminthic therapy and cancer.
- Patients who are pregnant. See the Helminthic therapy and pregnancy page for a detailed discussion on this.
Conditions that require a modified approach to helminth dosing
Helminths can produce much more severe side effects in people with certain conditions, including the following.
- fibromyalgia (see Helminthic therapy and fibromyalgia)
- chronic fatigue syndrome (CFS)
- myalgic encephalomyelitis (ME)
- multiple chemical sensitivity (MCS)
- multiple food intolerance
- narcolepsy (see Helminthic therapy and narcolepsy)
- eosinophilic esophagitis / eosinophilic oesophagitis (EoE)
- eosinophilic gastroenteritis (EG)
- mast cell disorders (see Helminthic therapy and mast cell disorders)
- mitochondrial dysfunction
- some lung diseases, especially those associated with scleroderma (see Helminthic therapy and scleroderma)
While people with any of these conditions can still self-treat with helminths, they need to:
- start with very small doses. For example, no more than 3 larvae if using NA. In the case of TSO, see, TSO dosing for hypersensitive individuals.
- only add further doses after all side effects from the previous dose have subsided.
- increase the size of subsequent doses very gradually.
These recommendations are even more important for females with any of the above conditions, since they appear to experience a somewhat increased severity of side effects in comparison with males.
The safety of TSO
The approval certificate for TSO, issued by the Thai FDA, translates into English as follows.
TSO has been used experimentally in humans since scientists at Iowa University began to study it in 1995. Since then, it has passed all the evaluations required by the US Food and Drug Administration (FDA), the German Federal Institute for Drugs and Medical Devices (BfArm) and the appropriate medical agencies of Denmark, Switzerland, Austria and the Czech Republic. Gaining these safety approvals was a precondition for securing permission from these agencies to carry out phase 2 trials, which added further confirmation of TSO's safety.
- 2015 Nov Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect
- (Although the authors of this paper have made comment on a lack of benefit to subjects, the trial was only designed to assess the safety of TSO and not its efficacy. It would not have been capable of demonstrating any significant benefit because it used a treatment period of only 12 weeks, which is inadequate when assessing the efficacy of a helminth. It also used a novel TSO formulation with a pH of 5, when it is known that storage of TSO at a pH above 4 may impede its therapeutic effect in humans. )
- 2013 Aug Randomised clinical trial: the safety and tolerability of Trichuris suis ova in patients with Crohn's disease -- Full text | PDF
- 2003 Sept Trichuris suis seems to be safe and possibly effective in the treatment of inflammatory bowel disease
Also see: The question of possible TS persistence.
The safety of HDC
Helminths such as the human hookworm (NA) and the porcine whipworm (TSO) have been tested for adverse side effects in published, controlled clinical trials. Although several animal studies have shown efficacy of HDC in protecting against chemically-induced colitis,  the therapeutic effect of HDC has not yet been tested in a human trial. However, William Parker and colleagues at Duke University have systematically compiled records of individuals self-treating with helminths. Although these sociomedical studies are generally not designed to quantitatively assess the risk of adverse side effects, the Duke team has been able to obtain some semi-quantitative information from physicians who supervise patients self-treating with certain helminths, TSO and HDC in particular. When considering adult self-treaters, the Duke team has noted that adverse side effects from use of HDC are dose dependent and generally mild, involving temporary diarrhea following administration of a dose that is relatively high for a given individual. (Most individuals use therapeutic doses that are below their personal threshold for induction of diarrhea.)
A considerable number of cases of paediatric use of HDC were reported to the Duke team, and the quality and quantity of adverse side effects was different in this population than in the adult population. Most paediatric individuals using helminths in the Duke sociomedical studies were attempting to treat neuropsychiatric disorders (for example, ADHD associated with autism), which heavily biases the available information. Based on physicians’ reports to the Duke team, most individuals with autism experienced a slight but transient increase in hyperactivity following self-treatment. This was not considered a reason to discontinue therapy by most individuals, but rather was considered an early indicator that the HDC were having a beneficial effect. (Similar observations were made with TSO use in the paediatric population.)
More troublesome adverse reactions were noted in about 1% of the paediatric population taking HDC and were considered cause for cessation of therapy. Adverse reactions were of two types: firstly, severe gastric pain associated with documented colonisation (adult helminths growing in the gut - see Risk of HD maturation and persistence) and, secondly, worsening of behavioral symptoms. These more troublesome effects were relieved by treatment with anthelmintic drugs. Behaviour usually returned to baseline in these cases within one to three weeks of treatment, based on physician’s reports to the Duke team. Based on available data, Parker estimates that the chance of having a very favourable reaction to HDC compared to a very negative reaction is about 25 to 1 (favouring a very positive reaction) in the paediatric population. However, again, this number is based on experiences of self-treaters with neuropsychiatric disorders and was obtained using a sociomedical study design that is semi-quantitative in nature. In the adult population, the Duke study suggests that the chances of a very negative reaction may be much less than in the paediatric population, but insufficient numbers have been obtained to reach any conclusions. (William Parker, personal communication February 2017 commenting on over 700 cases of self-treatment with HDC.)
Can H. diminuta mis-migrate to organs outside the digestive tract?
There are no reports in the scientific literature describing mis-migration in humans by H. diminuta. There are numerous articles describing the colonisation of humans by HDC (see Risk of HD maturation and persistence), but none of these mentions mis-migration.
The safety of NA
The safety of controlled infection with NA has been confirmed in studies at universities in the UK and Australia.
- 2011 Mar Effect of hookworm infection on wheat challenge in celiac disease - a randomised double-blinded placebo controlled trial -- Full text | PDF
- 2009 Jul Safety of hookworm infection in individuals with measurable airway responsiveness: a randomized placebo-controlled feasibility study -- Full text | PDF
The Centers for Disease Control and Prevention of the United States Government Department of Health and Human Services have determined that "light" hookworm infections require no treatment, and the infection levels used in helminthic therapy are all considered to be "light". (In 1991, the World Health Organisation defined a light hookworm infection as one producing fewer than 1,000 eggs per gram of faeces, and, in 2002, as one producing less than 2,000 epg of faeces.)
Therapeutic dosing with NA should follow the guidelines established by the helminthic therapy community and set out on the following page.
The use of larger doses than those recommended can result in side effects, which can be severe and, in one case, caused eosinophilic pneumonia.
In another reported case, excessive dosing with hookworms appears to have caused organ damage, which fortunately proved to be reversible with anthelmintic treatment.
In spite of the safety of "light" doses of NA having been established, there are four questions that occasionally concern those considering self-treatment with this species.
Can hookworms act as a vector for pathogens?
The commercial providers of NA use an antimicrobial wash to clean their larvae, and ship them in a weak antibiotic solution. Since helminths are living organisms, it is impossible to sterilise them completely without killing them, but a review of the literature found no reports of NA transmitting a secondary infection.
The providers also periodically test their reservoir donors for a range of communicable diseases such as HIV and hepatitis.
Interestingly, once hookworms have entered their host, they appear to engender a milieu that is generally less permissive of pathogenic bacteria. This became evident when blood from individuals hosting hookworms was shown to have a significantly greater ability to control virulent mycobacterial growth (including that of Mycobacterium tuberculosis) in vitro than blood from subjects without hookworms. This benefit, which is possibly mediated by helminth-induced eosinophils, was lost following treatment with an anthelmintic drug.
Can hookworms mis-migrate to organs outside the digestive tract?
There are no reports in the scientific literature describing mis-migration in humans by NA and several authorities have made it clear that NA does not mis-migrate in our species.
Mis-migration can occur with some species of helminth that are not adapted to living in humans, such as the roundworm species of dogs and raccoons, which are well known for migrating to the brain and eyes after entering a species to which they are not adapted. And there may be an increased risk of mis-migration by these and other species in people who are severely immunocompromised, for example someone with HIV/AIDs. However, inoculation with NA has been reported to be safe, even in patients who are immune-suppressed.
Do hookworms cause tissue damage?
When they feed, mature Necator americanus hookworms create a microscopic break in the surface of the mucous membrane lining the intestine which biologists refer to as 'ulcers', and a number of these sites will be produced by each worm as it moves to a new location every few hours. However, it is important to remember that an adult hookworm’s mouth is a little narrower than its body and that its body is only as thick as a few human hairs, so these 'ulcers' really are tiny and they heal quickly, in part due to the localised first aid administered at their feeding sites by the worms themselves in the form of healing secretions.
These 'injuries' caused by hookworms are insignificant when compared with the massive operation of planned demolition and reconstruction that is going on throughout the bodies of humans at all times and which, for example, 'destroys' more than 50 billion cells every day and replaces them with new ones. This natural process of tissue breakdown and repair is what keeps humans alive for several decades, but the words that biologists use to describe these processes can cause concern to non-biologists whose viewpoint is inevitably much more subjective.
Hookworm larvae also cause what biologists refer to as tissue 'damage' when they break through the blood capillary walls to enter the alveoli of the lung during their migration from the skin to the intestine, but the resulting holes are microscopic and heal very quickly thanks to repair mechanisms that deal automatically with such events.
For more details about this healing process, see the papers from which the following quotes are taken.
There is evidence that the migration of hookworms through the lungs may have direct beneficial effects for the host, for example by reducing their susceptibility to tuberculosis.
Do hookworms cause excessive blood loss and anaemia/anemia?
The fact that hookworms create tiny wounds when they feed, and that these continue to bleed briefly after the worms have moved to new feeding sites, has led to concern that NA might cause excessive blood loss and consequent anaemia. This notion has arisen partly because NA is often confused with the other prevalent human hookworm, Ancylostoma duodenale (AD), the 'Old World' hookworm, which causes nine times more blood loss than NA. In the case of NA, there is arguably a greater risk of anaemia attached to diagnostic blood testing and blood donation than there is from hosting this species of helminth. The 1.09 liters of blood that is estimated to be drawn each year by a colony of 100 NA (a single NA can take 30 microliters of blood per day) is significantly less than the 2.88 liters of blood that an adult weighing 100 lbs or more is permitted to donate annually. For more detail, see Helminthic therapy and nutritional deficiencies.
Even the additional bleeding from hookworm feeding sites that is caused by a host taking a drug or supplement with a blood thinning effect - such as the antimalarial drug, hydroxychloroquine (Plaquenil, etc.) or the herb, ginko biloba - is unlikely to present a problem unless the patient’s clotting time, or INR (International Normalized Ratio) is already significantly raised, or they have a very large worm colony, or an existing predisposition to iron deficiency anaemia. There is therefore no need to avoid products that have a blood thinning effect while hosting hookworms, unless there is a preexisting issue with clotting, and, even in this case, it is unlikely there would be a problem. Several people who are hosting a therapeutic number of hookworms have even been able to maintain INR at a level of 2-3 while also taking potent anticoagulant drugs such as heparin. And hydroxychloroquine (Plaquenil, etc.) does not significantly increase clotting time so should not be a problem if taken while using hookworms.
Can hookworms make their hosts' blood too thin?
The fact that hookworms secrete anticoagulants to assist their digestive process can raise concern in the minds of patients with coagulopathy - a condition in which the blood’s ability to form a clot is impaired. However, the amount of anticoagulant produced by NA is minute, and its effect is mostly localised to the worms' feeding sites, so it is unlikely to pose any risk to self-treaters who are only hosting a therapeutic number of hookworms. Even most of those individuals for whom clotting was a pre-existing issue do not experience any significant change in their clotting time after inoculation with NA. Nevertheless, patients with coagulopathy should monitor their clotting time after inoculating with hookworms as a precaution to ensure that this remains optimal. Clotting time should also be checked by anyone who experiences any unexplained, spontaneous bruising.
There has only been one report by a hookworm self-treater that indicated a decrease in coagulation following inoculation with NA.
Can hookworms multiply within a host?
It is not possible for NA to multiply within a host because its eggs need to go through a period in soil in order to commence their development into worms. Once they have been deposited into the soil, the eggs will access nutrients from the faeces in which they were passed. Given adequate warmth, shade and moisture, they will then embryonate and, within a couple of days, hatch into larvae. While remaining in the soil, the larvae will go through two moults over the course of a week before becoming infective. Once these microscopic L3 larvae find a host, they will begin their migration from the host's skin to their small intestine, where the larvae will become adult hookworms and reliably remain for the rest of their lives. The progeny of these worms will follow the same very predictable lifecycle as their parents after passing out of their host in faeces. For more detail, see The developmental stages, migration and diet of Necator americanus.
Can hookworm hosts infect other people?
The washing of hands, along with the use of a flush toilet, or one connected to a septic tank that is always emptied before becoming full, will remove any risk of a hookworm host infecting others.
Composting toilets have a generally low pathogen destruction rate and are unlikely to kill hookworm eggs, which would require high temperatures or long composting times. Therefore the material obtained from a composting toilet that has been used by a hookworm host needs to be handled, and disposed of, in a way that prevents human exposure, either directly via skin contact, or indirectly as a result of handling or consuming raw food products grown in ground to which the material has been added as fertiliser.
In order for a hookworm infection to be passed to another person in the wild, a hookworm host would need to defecate in sandy, loamy soil in a warm, humid climate and for another individual to then expose their bare skin to the ground or low vegetation at the defecation site at any time from a few days up to 5 months later.
Hookworms do not thrive in clay soils, where the ground temperature gets very cold, or when the faeces are deposited six feet or more below the ground surface. Hookworms were effectively wiped out in the southern US by pit privies (PDF) and septic tanks.
Campers should note that, since hookworm larvae can climb six feet through sandy, loamy soil, defecating into a shallow hole in the ground in this type of soil will not provide protection against infection transmission. So, in order to protect other people and animals, any hookworm host needing to defecate in the wild should dispose of their waste safely by using one of the following methods.
- Bagging. Mountaineers carry plastic bags with them to avoid fouling the environment.
- Boiling. Any hookworm eggs or larvae contained in faeces that are heated in water should be dead before it reaches boiling point, but faeces should be boiled for at least 5 minutes to make certain.
- Burning. Cowboys in the American old West are reputed to have burned sun-dried cow pats on their camp fires, so perhaps the same method could be used for the disposal of human waste.
For more detailed information, see the Integrated Guide to Sanitary Parasitology.
Could there be dog hookworm larvae in NA doses from providers?
All the hookworms in captivity today, both those in the laboratories of research establishments and those maintained by the helminth providers, are likely to have originated from one of two sources. Firstly, the specimens collected from Papua, New Guinea, by Prof David Pritchard and his colleagues at Nottingham University, and, secondly, those jointly collected from the wild by the first two commercial suppliers of hookworms, Garin Aglietti and Jasper Lawrence, who were cooperating at that time under the banner of Autoimmune Therapies (AIT).
All the hookworms in use in research laboratories around the world were sourced from Pritchard, and all the hookworms available today from helminth providers are the descendants of those originally captured by Aglietti and Lawrence. Pritchard himself identified his hookworms as Necator americanus (NA), and AIT’s stock were also identified, by means of PCR testing, as being NA.
The notion that there might be dog hookworm larvae amongst doses of NA has only ever been suggested by researchers at the Malaghan Institute in New Zealand. They have claimed repeatedly, in interviews given to the press, that individuals who are self-treating with hookworms purchased online might be infecting themselves with dog hookworms. However, these claims, which were all made in interviews intended to promote the Malaghan Institute’s own hookworm research programme, are without foundation. And they are just one of a number of misrepresentations by Malaghan staff about the activities of the self-treatment community, of which they clearly disapprove.
The Malaghan Institute’s Research Director, who has spent many years trying to develop a vaccine to eradicate hookworms - but still without success in 2021 - has a particularly jaundiced view of helminthic therapy self-treatment, and takes every opportunity to make disparaging comments about the community of self-treaters. For details, see Graham Le Gros and helminthic therapy.
If a human becomes infected by a dog hookworm, this is very obvious, because dog hookworms - whether Ancylostoma braziliense, Ancylostoma caninum or Uncinaria stenocephala - are unable to penetrate the basal membrane in human skin, so remain confined to the upper dermis, causing a very distinctive surface manifestation known as cutaneous larva migrans This phenomenon has never been reported by anyone who has purchased hookworms from the helminth providers listed in this wiki.
Even when humans do become infected by dog hookworms, the infection is self-limiting and causes no long-term pathology. If not treated with either oral or topical anthelmintics, the larvae of canine-adapted hookworms usually die in humans within weeks, and, while individual dog hookworm larvae have been reported, in a few rare cases, to have reached the lungs in humans, they never mature, progress to the intestines, or reproduce.
- A prescription for clinical immunology: the pills are available and ready for testing.
- Parasitic worms and inflammatory diseases.
- Review series on helminths, immune modulation and the hygiene hypothesis: the broader implications of the hygiene hypothesis.
- Overcoming evolutionary mismatch by self-treatment with helminths: current practices and experience.
- Practices and outcomes of self-treatment with helminths based on physicians' observations.
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- Parasite role reversal: worms on trial.
- Human helminth therapy to treat inflammatory disorders - where do we stand?
- Helminthic therapy: improving mucosal barrier function.
- Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders.
- Reconstitution of the human biome as the most reasonable solution for epidemics of allergic and autoimmune diseases.
- Got worms? Perinatal exposure to helminths prevents persistent immune sensitization and cognitive dysfunction induced by early-life infection.
- A case report of a Hymenolepis diminuta infection in a child in St James Parish, Jamaica
- Neutralizing anti-IL-10 antibody blocks the protective effect of tapeworm infection in a murine model of chemically induced colitis
- Extracts of the rat tapeworm, Hymenolepis diminuta, suppress macrophage activation in vitro and alleviate chemically induced colitis in mice
- Infection with Hymenolepis diminuta is more effective than daily corticosteroids in blocking chemically induced colitis in mice
- IL-22 Restrains Tapeworm-Mediated Protection against Experimental Colitis via Regulation of IL-25 Expression
- Hookworm, Ascaris lumbricoides infection and polyparasitism associated with poor cognitive performance in Brazilian schoolchildren
- Hookworm: "the great infection of mankind”
- Facebook Helminthic Therapy Support group post.
- Symptomatic hypereosinophilia associated with Necator americanus self-inoculation
- Yahoo Helminthic Therapy forum post 4330
- A proof of concept study establishing Necator americanus in Crohn's patients and reservoir donors
- The hookworm pharmacopoeia for inflammatory diseases
- Yahoo Helminthic Therapy forum post 7254
- Blood and guts: The intestinal vasculature during health and helminth infection
- Programmed Cell Death and Inflammation: Winter Is Coming
- Helminth Modulation of Lung Inflammation
- How the parasitic worm has turned
- Myeloid-Restricted AMPKα1 Promotes Host Immunity and Protects against IL-12/23p40-Dependent Lung Injury during Hookworm Infection
- Role of Macrophages in the Repair Process during the Tissue Migrating and Resident Helminth Infections
- Frequency of blood tests in heart surgery patients may lead to anemia, transfusions
- Parasitic infections. Treatment and developmental therapeutics. 1. Necatoriasis
- Yahoo Helminthic Therapy forum post 5275
- Yahoo Helminthic Therapy forum post 5233