Parasitic Worms Ease IBD

May Reduce Overactive Immune Response Behind Crohn's Disease, Ulcerative Colitis

Sept. 23, 2003 -- The thought of swallowing live worm eggs may turn your stomach, but that's exactly what researchers say may safely relieve the abdominal distress caused by inflammatory bowel disease.


Each year, about 600,000 Americans are diagnosed with IBD, a condition that consists of a spectrum of disorders that vary with cause and degree of intestinal inflammation. Crohn's disease and ulcerative colitis are the two major, chronic inflammatory diseases that cause inflammation and ulcers in the lining of the digestive tract. This results in severe pain, diarrhea, and gastrointestinal bleeding.


However, in about one-third of the world -- primarily underdeveloped countries with poor sanitary conditions -- these diseases are practically nonexistent. And some researchers speculate it's because those residents may be protected against IBD by having an abundance of parasitic "helminths," a scientific classification for various types of parasitic worms that live in the intestines of humans and animals.


"It turns out that countries where IBD is common are those industrialized, developed nations like the U.S., where there are no intestinal helminths. Conversely, where helminths are prevalent, the incidence of IBD is very low," says gastroenterologist Robert W. Summers, MD, of the University of Iowa College of Medicine.


"In fact, Crohn's and ulcerative colitis really emerged in the U.S. during the 1920s and 1930s, when we began to shift to improved plumbing and sanitation and we no longer fertilized soil with both human and animal waste," he tells WebMD. "Until then, these parasites were very common. And we didn't have much IBD."

Besides protecting against IBD, Summers' research indicates that parasitic worm eggs may also provide relief to those with Crohn's and ulcerative colitis, which typically strikes during the teens or 20s and can last a lifetime.

He and his colleagues administered to seven IBD patients a solution containing thousands of eggs of Trichuris suis, the so-called "whipworm" (named for its whipping tail) commonly found in the intestines of pigs.


During the initial treatment and observation period all the patients showed evidence of improvement, defined as improved scores in a quality-of-life questionnaire and as a drop in a symptoms score. "All had active IBD when the study began and weren't doing well on medications," he says. "On the initial dose, we noticed an improvement, but their symptoms recurred. So we continued with additional doses every two weeks. Some patients have continued getting the doses for years now and are doing well. And we have yet to detect any side effects in any patient."


Each dose contained about 2,500 live whipworm eggs, harvested at a USDA laboratory.


His findings, reported in the September issue of the American Journal of Gastroenterology, were originally presented before at an American Gastroenterological Association conference in 1999. The Iowa team is currently conducting two other studies, involving about 100 patients, in which half get the worm egg solution and the others get a placebo mixture. The patients don't know which liquid they receive. Worms for Future Treatment?


IBD is believed to be among the "autoimmune" disorders that includes lupus, multiple sclerosis, and psoriasis and may result from an overactive immune response, in which cells that normally attack invading disease and infection instead target healthy tissue. With IBD, the immune system may overreact to normal intestinal bacteria, causing inflammation and gradually eating away at the intestinal lining.


Summers says the worm eggs decrease this overactive immune response, possibly by secreting a substance.


"We know that people with certain colonized worms in their digestive tracts have a reduced immune response," he tells WebMD. "Therefore, we're hopeful that this treatment may someday prove useful for other autoimmune diseases."

In fact, Crohn's and ulcerative colitis are often treated with medications that suppress immune response (immunomodulators), such as AZA and Mexate. Other IBD drug treatments include antibiotics, corticosteroids such as Prednisone, or aminosalicylates such as Azulfidine and Dipentum.

More recently, some patients have been treated with "probiotics" -- bacteria given specifically to retain remission that appear to work as well as immune-suppressing drugs, says IBD expert Seymour Katz, MD, past president of the American College of Gastroenterology and clinical professor of medicine at New York University School of Medicine.

"So it's not that much of a galactic leap to say, 'Let's go one step further and introduce these worms to change the immunologic response of IBD patients," Katz tells WebMD. "This is certainly an intriguing concept that has merit, but the data is still very premature. And knowing the litigious nature of society, in addition to the fact that most people are repulsed by the thought of being given worms, there's a lot of baggage that needs to be overcome."

Unlike other parasites that can cause infection, the pig whipworm doesn't cause problems because it's not recognized by the human body as a foreign invader, and only colonizes for a few weeks. The Iowa researchers have also tested three other types of parasitic worms in studies of mice induced with a form of colitis. All have been effective, says Summers.

"These worms have been around for 3 million years," he says. "And one-third of the world's population is walking around with them in their GI tracts today and apparently having no problems."

Show Sources

SOURCES: Summers, R, The American Journal of Gastroenterology, September 2003'; vol 98: pp 2034-2041. Robert W. Summers, MD, professor, internal medicine, University of Iowa College of Medicine, Iowa City. Seymour Katz, MD, clinical professor of medicine, New York University School of Medicine, New York City; attending gastroenterologist, Northshore University Long Island Jewish Medical Center, New Hyde Park, New York; past president, American College of Gastroenterology, Arlington, Va.

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