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Worm therapy: How parasites could help us treat allergic diseases

16 May 2014

Parasitic worms have a reputation for causing disease. So the idea of being deliberately infected with them to improve your health might seem, literally, hard to swallow.

A few decades ago the same could probably be said of bacteria. Yet probiotic capsules containing billions of live bacteria are now taken routinely to stimulate digestion and boost immunity, particularly after prolonged antibiotic use. So why not worms?

The idea of taking a dose of worms to improve health is actually not as farfetched as it might sound. In the past decade there have been several clinical trials overseas investigating the potential of using live helminth worms (specifically pig worm and whipworm eggs – not the kind you find in your garden) to calm the gut inflammation associated with ulcerative colitis, IBD and Crohn’s disease. In recent years there has also been considerable interest in helminth worm therapy for autoimmune disorders such as multiple sclerosis. Although the treatment isn’t for everyone, patients involved in the studies reported an easing of their symptoms, with minimal adverse effects.

The reason helminth therapy is thought to have such promise is simply because parasitic worms are so successful at controlling the gut environment they live in. Parasitic worms are eradicated from the body when the immune system elicits a response called the Th2 (allergic) immune response. This is the same immune response that gives rise to the symptoms of asthma and allergy. As the parasitic worms do not want to be kicked out of their host when the Th2 immune response is activated, they have developed ways of keeping the host immune system in check.

Professor Graham Le Gros hypothesises that, if we can learn how the worms suppress the allergic immune response, we could do the same to treat asthma and allergy naturally.

Above image: Heligmosomoides polygyrus - one of the parasitic worms we study here at the Malaghan Institute. The bright area visible in the centre of the body is composed of future eggs that mature all along the mother’s body and can be found fully formed a few coils later. Image courtesy of Adeline Peignier.