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.

• chronic fatigue syndrome (CFS). See Helminthic therapy and ME/CFS
• depression, especially if severe. See Temporarily increased depression
• eosinophilic esophagitis / eosinophilic oesophagitis (EoE)
• eosinophilic gastroenteritis (EG)
• fibromyalgia. See Helminthic therapy and fibromyalgia
• helminth permissive immunity, as a result of genetic factors enabling prolonged persistence of helminths
• lung disease, especially if associated with scleroderma. See Helminthic therapy and scleroderma
• mast cell disorders (MCAD, MCAS). See Helminthic therapy and mast cell disorders
• mitochondrial dysfunction
• multiple chemical sensitivity (MCS). See Helminthic therapy and multiple chemical sensitivity (MCS)
• multiple food intolerance
• myalgic encephalomyelitis (ME). See Helminthic therapy and ME/CFS
• narcolepsy. See Helminthic therapy and narcolepsy

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 and, in the case of TSO, see TSO dosing for hypersensitive individuals,
• only add a further dose after all side effects from the previous dose have subsided,
• only increase the size of subsequent doses very gradually,
• be aware of the possibility that the size of doses may need to be limited indefinitely.

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.

According to the request for classification and export permission of TSO as a medicine for the therapeutic treatment of inflammatory bowel diseases (Crohn`s disease and ulcerative colitis), the food and drug administration committé has discussed the therapy and all manufacturing details. The committé recognized the intended use for the curative treatment of humans and decided TSO to be a drug according to paragraph 4 of the drug law from 1967. The production method shows that TSO is derived from animals as a complete biological organism, remains unchanged and is not mixed with another drug or synthetic solution. Therefore we decided that TSO is classified under the category of natural medicines like herbals, which are exempted from the drug registration requirements according to paragraph 79 of the drug law from 1967. (Director Drug Control, Deputy Director of the FDA Committé) [1]

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. [2])

• 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 mismigrate to organs outside the digestive tract?

There are no reports in the scientific literature describing mismigration 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 mismigration.

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.)

• CDC Hookworm Diagnostic Algorithm

Therapeutic dosing with NA should follow the guidelines established by the helminthic therapy community and set out on the following page.

• Hookworm dosing and response

The use of larger doses than those recommended can result in side effects, which can be severe and, in one case, caused eosinophilic pneumonia.

When I started, I took waaay too many hw, and too fast. My third dose exceeded my body's tolerance for hw and I developed eosinophilic pneumonia which showed no signs of abating after 5 months. My eos got up to 22%. I took albendazole to (mostly) terminate my colony. 6 weeks later, my pneumonia hadn't improved significantly. My symptoms only improved after reinoculating with a small dose of 6 hw. After healing from the pneumonia, I had no adverse symptoms.

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 several 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.

• Potential Transmission of Pathogens Between Human Hosts by the Hookworm, Necator Americanus (PDF).

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 mismigrate to organs outside the digestive tract?

There are no reports in the scientific literature describing mismigration in humans by NA and several authorities have made it clear that NA does not mismigrate in our species.

Over 700 million people remain infected with hookworms... Auto-reinfection, direct person to person infection, aberrant migration, and hypobiosis do not occur.

Necator americanus migration in humans is predictable, via the lungs (larvae) to the gastrointestinal tract (adults worms).

The "Old World Hookworm", Ancylostoma duodenale (which is not generally used in helminthic therapy), can mismigrate and may, in very rare cases, cause pancreatitis by entering the hepatopancreatic duct, where it can cause inflammation and, potentially, blockage of the duct.

Mismigration can also occur with some other 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 mismigration 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.

… both helminth- and host-derived factors contribute to establishing a state of vascular tolerance to limit tissue damage and promote repair.

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.

While the migrating larvae of hookworms cause mechanical and enzymatic damage to the lung parenchyma and epithelium... there is remarkable repair of pulmonary pathology postmigration.

The host uses its immune system to regulate the damage caused by the bacteria and the worms.

For more details about this healing process, see the papers from which the following quotes are taken.

… AMP-activated protein kinase (AMPK), a key driver of cellular energy, regulates type 2 immunity and restricts lung injury following hookworm infection.

Here, we analyze some of the studies regarding the role of AAMs in tissue repair during the tissue migration of helminths.

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.

Studies show that even a transient exposure to hookworm not only recruits innate cells to the lungs (both eosinophils and alternatively activated macrophages), and induces changes in T and B cells, but can also produce long-lived alterations in the pulmonary immune environment that may have a role in enhancing subsequent responses to respiratory pathogens, including M.tb

Can hookworms cause granulomas?

Some helminths can cause the formation of granulomas following mismigration, especially in unfamiliar hosts. For example, Toxocara canis, which normally only infects dogs, but can occasionally occur in humans, where granulomas caused by mismigrated larvae have been observed. [3]

Necator americanus (NA) has only been associated with granuloma formation in experimentally infected golden hamsters, which are not the definitive host of this species.

Histological examination showed that challenging L3 were trapped in the skin of primarily infected hamsters and surrounded or infiltrated by different inflammatory cells. The trapped L3 were damaged and dead followed by the formation of granulomas encasing dead worms. [4]

In humans, which are the definitive host of NA, this species does not mismigrate (see Can hookworms mismigrate to organs outside the digestive tract?) so granuloma formation is extremely unlikely and has not been reported in the scientific literature.

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 an estimated 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.

I take a drug that has a blood-thinning side effect (flurbiprofen, a cousin of ibuprofen), so I clot slower than most people, and can't take any other medicine with a blood-thinning effect (e.g., ginko biloba) without getting clotting problems. A few weeks ago (about 4 months after first inoculating with NA) I started getting spontaneous bruises that looked just like the ones my mom gets when her coumadin (blood thinner) dose is too high. I immediately started taking a vitamin K2 supplement (which helps clotting among other effects) and that seems to have solved the problem. My belief is that the tiny, local anti-coagulant that all blood feeders secrete (to keep their dinner flowing) was just enough to kick my blood from too thin to way too thin, causing the bruising. (Links expired)

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.

Do hookworms pose a threat to patients with respiratory disease?

People with common respiratory conditions such as asthma are able to safely self-treat with hookworms as long as they follow established dosing guidelines. However, in cases of advanced lung disease, there is a risk of exacerbation, and the following report details an example of how self-treatment with hookworms exacerbated advanced respiratory disease in one patient, with fatal consequences. But there is more to this particular story than is revealed in the report published in BioMed Central Pulmonary Medicine.

• 2021 Dec 20 Rapidly progressive respiratory failure after helminth larvae ingestion -- Full text | PDF

The patient, whose case is described, was a Functional Medicine advocate and a prominent networker for scleroderma - a condition she had had for many years. She became interested in helminthic therapy in early 2017, and joined the Helminthic Therapy Support group on Facebook in April of that year. Having discovered that researchers had suggested that scleroderma may be due to an absence of helminths, [5] she began a conversation about the therapy with this wiki’s founder in June 2017. But she wanted to read all the material on this site herself and have a microbiome test carried out before commencing the therapy.

She was finally ready to start helminthic therapy in September 2019, and obtained her first dose of 5 Necator americanus (NA) hookworm larvae. She followed this with a dose of 15 larvae three months later, and was reporting encouraging results by the time she got her third dose, also of 15 NA. Unfortunately, this last dose proved to be too much for her and she developed Loffler’s syndrome, a type of eosinophilic lung inflammation that usually only develops following inoculation with much larger doses of NA than those she had used, and which, in healthy individuals, will typically resolve over a few weeks and require no treatment. However, in this case, the patient did not enjoy normal health.

She had been diagnosed with Lyme disease in 2009, when she was 35, before being given further diagnoses of Raynaud's phenomenon and Lupus the following year. Limited systemic sclerosis (scleroderma) was added three years later, and, in 2015, pulmonary arterial hypertension (PAH), interstitial lung disease (ILD) and pulmonary fibrosis, plus calcinosis in 2016, all associated with the scleroderma. In 2013, she was told by three different physicians to get her affairs in order because she would most likely die within 5-10 years, i.e., between 2018 and 2023. [6]

As a CRNA (nurse anesthesiologist), the patient was well aware that her lung conditions would have predisposed her to developing Loffler’s syndrome, and that this syndrome was, in turn, likely to exacerbate the lung diseases she had. However, in view of the benefits she had already experienced from hosting hookworms, she decided against termination of her NA colony, and, not wanting to go to hospital because of the prevailing COVID-19 pandemic, decided to self-treat at home with prednisone, the medication recommended for Loffler’s syndrome.

Unfortunately, unbeknown to her, she was also hosting a pathogenic helminth, Strongyloides stercoralis, which she suggested may have been acquired during her travels in Peru, Brazil, Guatemala and Ethiopia in 2012. This helminth would likely have increased her predisposition to Loffler’s syndrome due to its unique life cycle with an ability to cause continuous autoinfection in humans, resulting in chronic lung inflammation. And, to make matters worse, when a patient with S. stercoralis takes a corticosteroid medication such as prednisone, the resulting immune suppression can lead to Strongyloides hyperinfection syndrome, [7] with an estimated mortality rate of between 60–85%, [8] [9] and potentially leading to Acute Respiratory Distress Syndrome (ARDS). [10]

Eventually, there was no alternative other than admission to hospital, where the S. stercoralis infection was discovered, anthelmintics administered to terminate this - and inevitably also her NA colony - and high flow oxygen added to the treatment with prednisone.

Tests carried out at this point revealed that the pre-existing lung disease had advanced to the point where the patient’s lungs were, in her own words, “beyond repair,” and her doctors advised a double lung transplant. When all the transplant centres rejected her because of a paralysed oesophagus - which would have presented too high a risk for aspiration post transplantation - hospice care became the only remaining option.

Also see

• Helminthic therapy and scleroderma

Can hookworm hosts infect other people?

Hookworms cannot be transmitted by direct contact between someone hosting them and another human. The feces of hookworm hosts do contain hookworm eggs, but these eggs need to incubate for at least 4 or 5 days in specific conditions before they become infectious larvae capable of infesting another person.

The use of a flush toilet, or one connected to a septic tank that is always emptied before becoming full, along with normal, routine hygiene practices, will remove any risk of infectious hookworm larvae being passed between individuals in a domestic environment.

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 raw food products grown in ground to which the material has been added as fertiliser.

In a domestic situation without access to a sewer network, human waste can be collected in a suitable waterproof container and either frozen, or sterilised with boiling water. If using a larger container such as a bucket, sterilisation with boiling water would need to be carried out while the level of material in the bucket is still low. The sterilised material could then be composted.

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 humid, warm and shaded environment, i.e., in the tropical or sub-tropical zones extending roughly between parallel 36 degrees north and parallel 30 degrees south. Another individual would then need to 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 the use of 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 examples of the human hookworm, Necator americanus (NA), 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 Kar Kar Island, Papua New Guinea, by Prof David Pritchard and his colleagues at Nottingham University, [11] and, secondly, those collected from the wild by the first two commercial suppliers of NA, Garin Aglietti and Jasper Lawrence, who were cooperating at that time under the banner of Autoimmune Therapies (AIT).

All the NA in use in research laboratories around the world were sourced from Pritchard, and all the hookworms available from the helminth providers are the descendants of those originally captured by Aglietti and Lawrence. Pritchard himself identified his hookworms as 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 claimed repeatedly, in interviews given to the press prior to 2022, 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 disapproved at the time. For more 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.

See also

• Helminthic therapy and cancer