Parasitic worms: Friend or foe?

Intestinal parasites infect more than a billion people world-wide, of which approximately 10% become ill. Although the thought of parasitic worms may be enough to turn people’s stomachs and put them off their food, for some sufferers of severe auto-immune diseases these worms may actually be able to provide relief or even remission of symptoms. We understand the negative effects worms can have such as nausea, vomiting and weight loss. However, research is now highlighting circumstances where their presence may indeed be beneficial in relieving symptoms of a number of diseases.

Helminthic therapy is a type of treatment where patients suffering from immune diseases are deliberately infected with parasitic intestinal worms in the hope that this will relieve their symptoms. Although this therapy is relatively new, there are a handful of promising studies indicating that worms may indeed represent a viable treatment for these diseases.

One of these studies was carried out by P’ng Loke, a parasitic immunologist. Loke’s work centred on the study of a man he met in 2007 who he later found had deliberately infected himself with parasitic worms. At first glance the man appeared to be perfectly healthy with nothing more than a genuine interest in parasites. However, it was soon revealed that, in an attempt to cure his inflammatory bowel disease (ulcerative colitis), he had infected himself with human roundworm which burrowed into the lining of his colon. Ulcerative colitis is an auto-immune disease characterized by open sores in the colon lining leading to intense abdominal pain and vomiting. Although the precise cause of this disorder is not well understood, severe cases have been linked to disruptions in mucus production within the colon. After coming across the controversial work of the parasitologist Joel Weinbeck, the man ingested a large quantity of the worm and was soon symptom free.

Endoscopic image of a bowel section known as the sigmoid colon afflicted with ulcerative colitis. The internal surface of the colon is blotchy and broken in places.

Colonoscopies of his intestines following infection revealed that wherever the worms formed colonies, there was a concurrent decrease in the number of ulcers. This decrease in ulceration is believed to be a beneficial side effect of the body’s immune response against these worms. Upon infection the body’s immune system increases production of both inter-leukin IL-22 (a protein important for healing the colon lining) and a number of mucus-producing cells found throughout the colon. This increase in intestinal mucus forms a protective barrier across the surface of the gut, protecting it from bacteria and thereby reducing inflammation.

Along with a possible role in the treatment of colitis in humans, studies in animals have found that infection with worms can either alleviate symptoms or entirely protect against diseases such as asthma, rheumatoid arthritis and some food allergies. A role in Crohn’s disease (a long term condition causing inflammation of the lining of the digestive system) has also been suggested. Results from a clinical trial show that ingestion of swine whipworm causes remission of symptoms in 72% of cases, and improvement but not remission of symptoms in a further 7%.

What is interesting is that the prevalence of auto-immune diseases in the developed world is high, but the incidence of parasitic worms is relatively low. In contrast, in the lesser-developed world where the incidence of worms is high, the occurrence of auto-immune diseases is sparse. Could it be that in our quest for sanitation and clean water, we may have damaged one of our friends, one of our bodies natural source of defence against itself; the intestinal parasite?

Although some cases show evidence that parasite infection may play a role in protecting against certain disorders, it is still impossible to predict how any one individual will respond to such an infection. Indeed, it may be the case that in some patients the worms may cause more harm than good. Therefore continued research into safe and effective forms of helminthic therapy is required before we can truly distinguish these parasites as friend or foe!

Post by: Sam Lawrence

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