Patients with other conditions, such as irritable bowel syndrome, have tried worm therapy elsewhere. It has eased symptoms without causing known side effects.

Many scientists believe the prevalence of such autoimmune conditions — including multiple sclerosis, allergies, asthma and a form of diabetes — is partly explained by a "hygiene hypothesis."

Sanitary environments in developed countries have led to more of the diseases, the theory goes, because people's immune systems aren't properly trained by exposure to germs and parasites.

The worm therapy offers a crash course of such training, Fleming said. "It stimulates the immune system in a good way."

He said the concept is similar to eating yogurt, which contains helpful bacteria that regulate digestion.

In the UW-Madison study, five patients with multiple sclerosis will sip a sports drink-like liquid every two weeks for three months. Each cup will contain 2,500 eggs of the whipworm, a tiny organism that commonly lives in humans and animals.

Though the human whipworm rarely causes illness, the study uses a pig version that is benign in people, Fleming said.

The eggs hatch into larvae, the size of an eyelash, that stick to the inside of the intestine. In killing the larvae, the body unleashes an extra dose of regulatory T cells, which dampen overactive immune cells.

Existing multiple sclerosis treatments, all of them injections, also try to block overactive immune cells.

But with the worm therapy, "instead of knocking down the bad parts of the immune system, we're pushing up the good parts," Fleming said.

He is buying the egg-containing liquid from Ovamed, a German company that harvests the eggs from pigs.

Multiple sclerosis can cause numbness, paralysis, blindness and other symptoms. Most patients have a "relapsing-remitting" form, in which flare-ups are followed by recovery periods.

Fleming will check to see if the worm therapy reduces the frequency or severity of flare-ups. Patients will also undergo monthly MRI scans to see if fewer lesions develop in the brain and spinal cord, where the disease destroys nerve cells.

If the study is successful, 15 patients will be enrolled in a follow-up trial for a year. Then a larger study might be launched comparing worm therapy with a placebo, or fake treatment.

Worm therapy is a promising alternative treatment for the 400,000 Americans with multiple sclerosis, said Dr. John Richert. He is vice president for research and clinical programs at the National Multiple Sclerosis Society, which is funding Fleming's study.

"We need to push for the development of new and safe medications," Richert said. "This is a direction that has a strong chance of bearing fruit."

Fleming admits he was skeptical when he first heard of worm therapy. It was carried out a few years ago by Joel Weinstock of the University of Iowa, who is now at Tufts University in Boston.

Zsuzsanna Fabry, a pathologist who worked with Weinstock in Iowa, is now at UW-Madison. She told Fleming of Weinstock's research, which had positive results in patients with irritable bowel syndrome.

Fleming figured the same approach could work in multiple sclerosis.

A study in Argentina backed up that hunch. It compared a dozen multiple sclerosis patients who were naturally infected with a similar worm with a dozen worm-free patients.

Over four years, those with the worms had 90 percent fewer flare-ups and brain lesions.

"This idea seems outrageous at first," Fleming said. "But many good, new ideas do."

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