Helminthic therapy is a relatively new treatment which takes the form of deliberate infection with the larvae or eggs of specially domesticated, benign, mutualistic intestinal worms.
Viewed from a medical perspective, this therapy is an experimental form of immunotherapy used in the treatment of chronic inflammation, autoimmune disease, and other immunological disorders, including allergy. It can also be seen simply as a form of probiotic treatment, using tiny animals instead of bacteria to reconstitute and enrich a depleted intestinal biome.
The legal position concerning helminths is still uncertain and untested in many countries, but is clearer in the US, where hookworms, whipworms, and rat tapeworms are currently classified by the Food and Drug Administration (FDA) as biological agents (i.e. drugs), as defined in Section 351 of the Public Health Service Act, and subject to an Import Alert.
The gradual loss of intestinal worms in industrialised societies from the mid-19th century, leading to their virtual eradication during the 20th century, has undoubtedly relieved these populations of the health issues associated with pathogenic helminths, but it has also led to inflammation-associated deficiencies in immune function that have contributed to widespread epidemics of allergy and autoimmune disease, as well as metabolic and neuropsychiatric disorders. However, this wasn’t recognised as a potential problem until the mid-to-late 20th century.
The first evidence that re-worming might prove beneficial was reported in 1948 after 25 patients had been relieved of their polycythemia as a result of being experimentally colonised by hookworms, and a parasitologist writing to the Lancet in 1976 described how the hay-fever he had suffered from for 25 years was completely relieved after he infected himself with hookworms.
While editing journal articles on parasites of the liver and intestine, Prof Joel Weinstock from Iowa University began to consider the possibility that the reintroduction of helminths might help his IBD patients. This eventually led to Weinstock carrying out ground-breaking studies in which IBD patients were given TSO, the ova of the pig whipworm, Trichuris suis, which were revealed to be safe and shown to produce improvements in disease activity.
The product used in the Iowa trials, which had been granted regulatory approval by the Thai FDA, became the first "therapeutic" helminth to be made available to the public when it was introduced for sale in 2003. The human hookworm, Necator americanus, also became available for purchase in 2007, followed by the human whipworm, Trichuris trichiura, in 2009. The fourth helminth to be domesticated for use in helminthic therapy was the rat tapeworm, Hymenolepis diminuta, which was first offered to the public in 2013, in the larval (cysticerci) form that was referred to as HDC.
Research had suggested that the use of these helminth species to reconstitute the human biome may be the best solution to the biome depletion caused by industrialisation, but the majority of clinical trials conducted during the first two decades of the 21st century produced lackluster results. The reasons for this have been suggested to include a variety of economic, regulatory, and practical issues surrounding the conduct of clinical trials, along with a failure to accommodate the nuances of therapy using living worms. Particular issues that clinical trials failed to address included the effect on efficacy of the formulation of helminth products, and the fact that the range of helminth doses typically needed within any cohort of individuals can vary by a factor of 10.
The poor results from the clinical trials were at odds with other strands of evidence that include numerous positive results in animal models, the positive results reported for individuals self-treating with helminths and the positive reports from clinical examination following accidental exposure to helminths.
Perhaps due to the disappointing results from clinical trials, medical researchers had, by the start of the third decade of the 21st century, largely switched from using living worms to working towards "helminth-derived product therapy" (HDPT) by seeking to create helminth-inspired pharmaceuticals identified from helminth excretory/secretory products and synthesised.
Some researchers are investigating the use of living helminths that have been custom engineered to perform specific purposes, such as seeking out and destroying cancer cells, or protecting soldiers from chemical and biological weapons.
In the absence of the availability from mainstream medicine of helminthic therapy using living worms, a global, online community comprising thousands of helminth self-treaters has taken over the development of the therapeutic use of living helminths, to the extent that this community has, according to one group of scientists, become the primary "laboratory” for helminthic therapy. These scientists have further suggested that, with the impetus no longer being provided by medical researchers, the self-treatment community’s “biohacking” endeavours may yet prove to be critical for public health by addressing the helminth deficiency that is a fundamental cause of disease in Western society.
Numerous scientists have expressed support for therapy using living worms, with some of them arguing that biome reconstitution will always be preferable to the use of synthesised pharmaceutical products. Living helminths also offer patients a self-administered, "probiotic" treatment that is very safe, remarkably effective, and available for immediate use from a range of suppliers.
Helminth infestation is probably effective against asthma and other allergic reactions because, by necessity for their own survival, helminths induce immunosuppressive activity in their host.
Organisms unsuitable for therapeutic use
- The giant roundworm (Ascaris lumbricoides — see illustration) has been shown to sometimes help against asthma, atopic dermatitis, and similar allergic reactions, but this is not a suitable species for therapeutic use.
- The beef tapeworm (Taenia saginata) has been used for weight loss, which has been called the "tapeworm diet". The "logic" behind this was that the tapeworm would reach your intestine and absorb the contents of the food you eat. This would allow you to eat as much as you want, as most of the calories and fat from the food would be going to the tapeworm(s), not to you. The problems are many. The tapeworm wouldn't "claim" most of your calorie intake. If you have a limited diet, the tapeworm will probably result in malnutrition. The tapeworm will also hijack several micronutrients. Although most beef tapeworm infections have no symptoms, and, given its size, this organism will no doubt excrete/secrete a large quantity of beneficial immunomodulatory molecules, there are times when the tapeworm can do real damage to its host, who may also eventually pass on the infection to others.
Numerous phyla of worm exist. Taenia saginata, mentioned above, is of the phylum Platyhelminthes (flatworms), which has not been used to date in helminthic therapy. Ascaris lumbricoides mentioned above is of the phylum Nematoda (roundworms), some members of which have been used in the therapy and are the subject of some of the peer-reviewed research described herein, as is Trichuris suis, the pig whipworm, which has also been tested for medicinal value. Despite broad similarities in appearance, the worms vary widely in their own biology as well as in their interaction with the human body.
- Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders.
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- Yes, people really did that.