A California man facing the prospect of having his entire colon removed to treat a severe case of colitis decided instead to try swallowing the eggs of parasitic worms.

Ulcerative colitis is an inflammatory bowel disease that can be debilitating. It's currently treated with drugs that don't always work well and often carry unpleasant side effects. The California man was able to find a Thai parasitologist who agreed to help him obtain the eggs. In Thailand, he swallowed 1,500 eggs of the human whipworm Trichuris trichiura.

Tissue taken when the colitis was in remission contained a high number of a different type of T-cell, a type that produces large amounts of interleukin-22, a compound which promotes wound healing.

Several months later, he was virtually symptom free, a condition which lasted for three years. When his symptoms returned, he underwent another round of therapy, this time swallowing 2,000 eggs, and got better again.

But the man wanted to find out why the treatment had worked. So he contacted P'ng Loke, Ph.D, a parasitologist who was then based at the University of California, San Francisco and is now an assistant professor in the Department of Medical Parasitology at NYU Langone Medical Center.

Helminthic therapy, the use of parasitic worms to moderate or calm the immune system, is an experimental therapy that has not been approved by any government body. It has, however, shown some promising results in treating autoimmune conditions, conditions where the body's immune system overreacts and begins attacking part of the body as if it was a foreign invader.

Dr. Loke does not advocate helminth therapy. In Loke's opinion, the California man was very lucky that he did not make a bad condition even worse. However, Loke was intrigued by the successful results of the treatment and agreed to study the man's case.

Loke compared blood and colon tissue samples taken while the colitis was active to those taken when it was in remission. Samples taken when the patient had active disease contained high numbers of immune cells called CD4+ T-cells. These cells produce large amounts of an inflammatory protein called interleukin-17. But tissue taken when the colitis was in remission contained a high number of a different type of T-cell, a type that produces large amounts of interleukin-22, a compound which promotes wound healing. The tissue taken while the disease was in remission also produced more mucus, which helps coat the tissue and reduces inflammation.

The increased mucus production may be an ineffective attempt at expelling the worms from the body; Loke likens it to a big sneeze.

There are currently helminth therapy studies underway that that use the pig whipworm, T. suis. Dr. Loke believes that these will be safer than studies using the human whipworm would be. Eventually, it may be possible to isolate the specific chemicals produced by the worms that dampen the immune response.

An article detailing Dr. Loke's study was published December 1, 2010 by Science Translational Medicine.