health & science

What gut worms could do for cancer

A medical trial looking at how hookworms affect healthy people could pave the way for hookworm prescriptions to help or prevent conditions from Crohn’s disease to cancer. It could also spell the end to a bitcoin black market of self-treatment with parasites.

Hookworms have been humans’ quiet but needy friends forever, secretly squatting in, and grazing on our small intestine.

Their camouflage mechanism developed to trick the human body into not noticing they’re having us for dinner could be the clue to protection from a range of inflammatory diseases.

Malaghan Institute of Medical Research director Professor Graham Le Gros has had a hookworm fascination for some time. Hookworms live for around 10 years inside the body and take an interest in keeping a healthy home.

“They graze over a little area of the small intestine, a circular patch. In your mind, imagine all the lovely little villi [grass like projections of the small intestine which transport nutrients to blood].

“You can imagine it [the hookworm], it just sort of crops there like little sheep, not too bad. Now and then it will take a good chunk and bleed you a bit. It has to secrete molecules all the time to keep the immune system from firing up and getting rid of it.”

A  simplified diagram of what hookworms graze on, a single villus from a human intestine.
Image: Snow93 Public domain

Hookworms’ ability to suppress the immune system just enough to ensure the body doesn’t evict them, but not so much their human banquet dies of another disease, could be a key to managing inflammatory diseases caused by overactive immune systems.

Their presence has been considered a possible reason there’s a lower incidence of inflammatory disease in some third world countries. 

But there's a catch. When it comes to hosting a dinner party in your intestines, it's best to limit the guest list. Too many grazing hookworms and the human host suffers. This can be seen in hot countries, where sanitation is poor and hookworm infections common.

“They can bleed you dry. They can stunt human’s health; they stunt a child’s development.”

In past times Le Gros said coal miners weren’t necessarily pale from lack of sun.

With toilet trips to the surface time-consuming, toileting often took place in quiet corners of the warm underground mines. Faeces with hookworm eggs were squelched throughout the mine, and onto ladder rungs, spreading hookworm eggs widely.

Leaky shoes provided a pathway to skin for hookworm larvae which then burrow to the lungs, and get coughed into the mouth. From there it’s an easy trip from the digestive system to their eventual squat in the small intestine where they graze.

The pale skin and ill health once referred to as “miners’ anaemia” was actually the effect of hookworm infestations, sometimes affecting 80 to 90 percent of workers in a mine.

How hookworms really could be your friend

Le Gros calls hookworm our “cornerstone parasite” and when there’s a “Goldilocks” number, not too many and not too few, their effect is worth investigating.

While he’s neutral on the topic until there’s scientific evidence in humans, he said there is strong evidence in model systems that hookworms are potent suppressors of inflammatory disease.

He worries about what he calls an epidemic of young people with Crohn’s disease, where the intestine and bowel is inflamed. The end result is usually the need for a colostomy bag.

One possible cause is the immune system in developed countries isn’t getting enough of a workout. The hookworms’ presence could stimulate the system just the right amount so it works, without going into overdrive.

“I sound a bit like a madman, but that's because there's something going on in our developed world to do with the immune system that making it is making lots of people susceptible from an early period in life to these inflammatory diseases.”

Conditions which could be affected range from Crohn's to coeliac disease, asthma, allergies, multiple sclerosis and even cancer.

Colon cancer causes polyps on the colon wall. Le Gros thinks there's a chance worms may help protect against this.

“They stimulate mucous production. They make a lot of good mucous in the gut and it acts as a bit of a barrier for the insults and injuries the colon receives. Maybe we’ll see a reduction in colon cancer.”

At this stage, hookworms causing mucous which stops cancer is just a theory.

“You can get so much in love with these ideas. You've actually got to test them properly.”

He’s starting at the beginning, with healthy people. Fifteen volunteers will take 30 human hookworms and undergo a year of tests using all the “wonderful” tools available at the Malaghan Institute. Volunteers will supply stool samples, blood samples, and even swallow a camera pill during the study so contractions of the full intestine can be viewed.

Once that information is gathered and hookworms' effect on the human body is clearly understood, he said it might be easier to target what diseases could benefit most from hookworms and conduct further research.

The trial received enough volunteers just days after it was announced.

The likely reason for the trial’s popularity is the theory of beneficial worms has been around for some time and is quietly flourishing on social media.

Social hookworm media

There’s a thriving community on Facebook who have been busy self-treating themselves with helminthic (parasitic worm) therapy who affectionately refer to their worms as their “colony” or “friends”. The range of conditions treated is long, and the stories shared overwhelmingly positive.

Group members talk about how many worms they apply, how often they add more worms to their gut “colony” and ask questions about how to avoid killing their beloved gut friends.

“Is a Thai red or green curry safe for helminths?”

“Are topical antibiotic ointments okay?”

One topic not discussed much is how to go about getting worms. New members to the groups are sent to a page of supplier listings and told not to divulge to media where their worms come from.

For some suppliers, who fear running afoul of regulators, the only payment they’ll accept is bitcoin so they can retain anonymity. The cost ranges from hundreds to thousands of dollars and without regulation there’s no guarantee what’s paid for is what’s received. Reviews show some suppliers take the money and struggle to deliver the doses promised.

Another path is DIY. Some people choose to travel to countries where it's warm enough for hookworms to occur naturally and the sanitation is poor and walk barefoot. The risk to this approach is picking up different types of worms, some of which can be dangerous.

In other cases there may be charitable hookworm hosts who decide to grow larvae from eggs in their faeces and share them with others. Knowing how many larvae are in a donation requires a microscope, not just a magnifying glass, and webpages detailing the process suggest donors are tested for hepatitis and HIV.

“At the moment it [hookworms] are just passed from person to person in the most unreliable way, with no clear protocols on how to make a good healthy worm.”

If Le Gros’s work proves there’s a therapeutic role for hookworms suppliers will need to adhere to regulations around the supply of therapeutic goods.

Necator americanus - the hookworm species being researched. Photo: Supplied

You can’t breed a human hookworm outside of a human body, although Le Gros said the institute was investigating ways this could be done, how they could be stored frozen and how a "living pill" might work.

“Not to make money, just to make a reliable drug.”

The institute's work is funded by the Health Research Council. Le Gros said the worms were not something a pharmaceutical company was likely to research.

"If we can cure or stop colon cancer, it's going to be so cheap. It's going to put people out of business."

Medsafe's compliance management manager Derek Fitzgerald said Ministry of Health consent would need to be granted before hookworms could be legally sold as a medicine.

"If the trials find that human hookworms can offer the type of therapeutic benefits the Malaghan Institute is researching, they (and substances extracted from them) would be considered a medicine."

As well as needing efficacy and benefit to be proven, data on how they were produced and how quality was controlled would be evaluated as part of an approval process.

While it may seem odd, to regulate a living creature as a medicine, it's not unheard of. Leeches can be considered a medical device, and the enzyme they produce a medicine.

Le Gros points to cancer immunotherapy using living cells as another example. 

"It's a whole brave new world. It's pretty frightening for some people but I think we've got to do it. There's just too many needy people and it won't be solved by drugs."

Le Gros hopes the research will answer some of the many questions around the hookworms and people will find answers with scientific backing instead of having to rely on personal anecdotes on social media.

He said it’s unlikely a hot Thai curry would kill hookworms.

“They’re as tough as hell. They’ve evolved with us."

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