Dec 13 2004
Parasitic worms, or helminths, may be an effective treatment for the chronic inflammatory bowel disorder, Crohn's disease, suggests a small study in Gut.
Helminths, such as roundworms and threadworms, are rare in developed countries, where rates of Crohn's disease are high. But in developing countries where corresponding rates of the disease are low, many people carry these parasitic worms.
Their eggs contaminate food, water, air, faeces, pets and wild animals. And they are also found on toilet seats and door handles. Once inside the body, the eggs usually lodge in the bowel, where they hatch into worms.
Every three weeks, 29 adults with moderately active Crohn's disease swallowed 2500 whipworm eggs of the species Trichuris suis, commonly found in pigs. The eggs were disguised in a commercial drink. The volunteers repeated this exercise for a period of 24 weeks in total.
They kept daily diaries of their symptoms and were monitored every three weeks at the clinic.
Most of the patients had had their symptoms for around 4 years, and standard treatment had not worked.
Four of the patients had to withdraw before the half-way mark, and a further patient stopped the treatment when she became pregnant. But none of them had got any worse.
By week 12, 22 patients experienced a significant improvement in symptom score, and 19 patients had no symptoms at all. By week 24 the respective numbers had climbed to 23 and 21.
This translates into a response rate of 80% and a remission rate of 73%, say the authors. There was no indication that the helminth treatment had worsened symptoms and there were no side effects. But patients taking drugs to suppress the immune system at the same time tended to fare better
The authors say that helminths commonly found in people, such as tapeworms, have the potential to cause disease, but pig helminths have a short life cycle, which minimises the risk of colonisation. And once the eggs hatch, the worms stay in the bowel and do not invade the rest of the body.
Eggs are shed in the stool, but can't colonise another host until they have been incubated in the soil for several week, so are unlikely to pose a public health risk.
Crohn's disease is caused by an excessive immune response to normal gut bacteria, and helminths suppress the immune response and consequently dampen down inflammation.
The authors conclude that helminths could be a simple alternative to current treatment for Crohn's disease, or could be used in combination with other medication. They caution that their findings are based on a small number of people, but suggest that the results merit further investigation.
Dr Robert Summers (or Drs Elliott and Weinstock), Jones A Clifton Center for Digestive Diseases, Department of Internal Medicine, University of Iowa, Iowa, USA.
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