OPINION: Infecting yourself on purpose with parasitic intestinal worms may not seem like the healthiest thing to do. But a growing number of New Zealanders are doing just this, convinced that helminth therapy is the answer to managing the symptoms of a wide range of autoimmune and inflammatory conditions.
These self-treaters buy the larvae online, usually paying with bitcoin, and use a skin patch to apply them. The creatures burrow into their skin, then travel in the bloodstream to the lungs. Eventually they are coughed up and swallowed, and their journey ends in the intestine, where they attach themselves to the wall of the gut and live happily.
There is an ick factor to all of this, but also no shortage of anecdotal reports that it is an effective treatment.
“When you talk to these people, it’s hard not to believe in it,” says gastroenterologist Tom Mules. “They are so passionate, and clearly it’s made them feel better. But that’s not really how medical practice works. We need a proper evidence base to make sure it’s safe and effective before we start putting it into patients on a bigger scale.”
At Wellington’s Malaghan Institute, Mules leads a team that is busy exploring the therapeutic potential of human hookworms. The theory is that we co-evolved with these parasites over millions of years, and that by eradicating them in the developed world, we may have sparked a rise in autoimmune and inflammatory disease.
The science is showing that having a colony of hookworms in our gut seems to affect us in multiple ways. Perhaps most significant is that these parasites are able to manipulate their host’s immune system.
“The hookworm wants to live in the body for many years so it can produce eggs, and those eggs can then infect other people,” says Mules. “So it secretes molecules into your bloodstream, which suppresses parts of the immune system that are known to target parasitic infection. Lots of autoimmune diseases are caused by those same pathways it tries to suppress.”
Infection with hookworms may also change the microbiome, the colony of gut bacteria that is known to affect many aspects of health. And the parasites make the mucus layer that lines the intestine thicker and less penetrable, helping to prevent so-called leaky gut.
Hookworms are interesting as a medicine, but also complicated to explore. Why do some people react differently to an infection, for instance? Are there other factors involved? And what diseases could this sort of therapy most usefully target? These are all questions researchers hope to answer.
At Malaghan, they have now completed a clinical trial using healthy volunteers. “We’ve mapped out over the course of the year how a single dose of hookworm – that’s 30 hookworm larvae – manipulates the host’s immune system,” says Mules.
The researchers are now trialling helminth therapy for inflammatory bowel disease and getting some interesting results, he says.
Meanwhile, their collaborators at James Cook University, Cairns, are investigating the potential for hookworms to help prevent metabolic syndrome.
Since humans have lived with hookworms for so long, it is believed they are safer than most modern medications. Of course, they can also be very harmful. In developing countries, where people may be infected with large doses not only of hookworms, but other types of helminths, they are a cause of illness and malnutrition.
“In New Zealand, people aren’t getting infections from other places. They only get the dose we give, and it doesn’t replicate in the body, so from that perspective it’s very safe. We know that we can give people a single dose of hookworm and they still have that infection two to three years out.”
Although these infected people will shed eggs in their faeces, in this country that doesn’t present a health problem, either. “First, we practise Western hygiene. Also, our soil conditions aren’t right to propagate the worms; for that to happen the climate needs to be tropical all year round.
While the self-treaters continue to infect themselves, it is likely to be some time before helminth therapy is available as part of mainstream medicine.
“The dream is that we will be able to use it as a treatment for autoimmune or metabolic disease,” says Mules, “and then people won’t have to take daily medication for the rest of their lives.”
