Swallow your pride
Can parasites help treat autoimmune disease?
Swallowing live parasitic worms might sound more like a punishment than a cure, but some scientists believe that worms might be just the tonic for people with autoimmune conditions like Crohn’s disease and allergies like asthma.
The theory of using worms to treat disease is often linked to the ‘hygiene hypothesis’ (see ‘Under exposure’), which focuses on our modern obsession with cleanliness and its effect on our immune system. In the past, worm infections were more common, and some scientists think these parasites helped train the immune system to moderate its response to foreign substances so that it didn’t become oversensitive. In autoimmune and allergic diseases, the body overreacts to its own cells or foreign substances, respectively.
Treatments using worms are experimental – scientists haven’t carried out enough studies to really know whether they work. While some have produced exciting results, others have been less promising. In 2005, a group of US scientists published the results of a pair of studies testing whipworm in people with two types of inflammatory bowel disease – ulcerative colitis and Crohn’s disease. In both conditions, the immune system attacks the gut. In the ulcerative colitis trial, symptoms improved for 43 per cent of people who took whipworm compared to 17 per cent who took placebo treatment, while in the Crohn’s trial 79 per cent improved, with 72 per cent going into remission (where the disease went away).
However, in 2014, a review of the evidence for worm infection as a treatment for inflammatory bowel disease found that there was still not enough evidence to reach any conclusions about its safety or effectiveness. The ulcerative colitis trial from 2005 was included, but was judged to be small and of poor quality, while the Crohn’s disease trial was excluded altogether.
Meanwhile, UK researchers have recently shown that mice infected with nematode worms are protected against developing allergy. In the mice, the worms suppress the release of an immune signalling molecule called IL-33 (a cytokine), which is released in allergic responses. People who have asthma may have raised levels of IL-33 in their lungs.Lead image:
Yasser/Flickr CC BY