“There is a theory called the absent friends hypothesis,” says Kara Filbey, a researcher at Wellington’s Malaghan Institute. “Our immune systems evolved to have worms. We’re supposed to have some inside us, but now we’ve eradicated them completely in the Western world.”
To make a home inside the gut, worms need to be able to keep a lid on our immune system so it doesn’t attack them. Without them there to control the inflammatory response, the theory is that our system starts responding to things it shouldn’t, such as allergens in the environment.
“If you look at places where they do have worms endemically, such as Africa or Southeast Asia, they have a lower rate of allergies and inflammatory disease,” says Filbey.
She has been doing helminth research for a decade and is a bit of a fan. “Worms are amazing. They are big, multicellular organisms with their own microbiome and they have immune systems themselves, so they must be having a big effect on us.”
Research is taking place worldwide to discover exactly what effect parasitic worms are having, and how that might be used to benefit our health. Filbey’s latest project has proved they are not merely manipulating the immune system.
She worked with mice, first giving them a dose of a type of gut worm that naturally infects rodents in the wild. “That worm is inducing immune responses, obviously, as it’s a foreign object, but you wouldn’t know the mouse had it,” she says. “Some of them actually look healthier, with nice, shiny fur.”
Next, Filbey gave the same mice hookworms, which enter through the skin and migrate via the lungs to the gut. A surprising thing happened. Rather than dampening the immune system, the original gut worm induced an immune response, activating cells that circulate around the body and lodge in different organs. The immune cells attacked and killed the hookworm while it was still in the lungs.
So Filbey’s results suggest that living with a “friendly parasite” could protect humans against infection as well as autoimmune diseases.
There is still work to be done before GPs can start prescribing worms. The correct dose of the right worm is vital – a heavy burden can have disastrous consequences, stunting growth or causing anaemia, and is particularly harmful for children and pregnant women.
We also need to come up with a more streamlined way of producing helminths. At present, larvae for clinical trials are collected from the faeces of infected human hosts, before being cleaned and given as a treatment.
Some people are not prepared to wait until worm therapy is mainstream. Desperate for relief from a variety of conditions, including lupus and irritable bowel disease, they are buying worms online and self-infecting.
Ultimately, the aim is to pinpoint exactly how worms are protecting us. It may be they are secreting a molecule that can be delivered in the form of a pill or vaccine. “But it may be the worm’s microbiome doing the job, not the actual worm,” says Filbey. “We don’t know yet.”
Her latest work focuses on how worm infections can reduce inflammatory skin diseases such as dermatitis. So far, results are looking good.
“Atopic dermatitis and eczema is the first allergic disease you see early on in life. People then go on to develop other allergic diseases such as hayfever, food allergy and asthma. This is called the allergic march.
“We think when your skin is damaged at that early stage, allergens are able to sensitise your immune system and prime it to have an inflammatory response later on when you ingest that allergen or breathe it in. If we can target dermatitis and that early skin barrier dysfunction, then maybe we could stop the whole allergic cascade throughout your life from happening.”
This article was first published in the December 22, 2018 issue of the New Zealand Listener.