A New Prescription: Parasite Eggs

Whipworms are two-inch-long parasites that sicken pigs by burrowing into their guts. Scientists, however, are beginning to appreciate them for their curative power in humans. Large-scale trials underway in Europe are testing whipworm eggs as a treatment for autoimmune diseases such as Crohn's, a digestive ailment, and multiple sclerosis. About 23.5 million Americans have some type of autoimmune disorder. "This is probably the biggest market in the entire history of medicine," says Detlev Goj, founder of Ovamed, a German biotech. He believes whipworm eggs may prove effective against as many as 60 diseases.

Goj, who in 2002 got European regulators to approve the use of maggots to clean wounds, became interested in whipworms after coming across a 2005 study in which 21 out of 29 patients with Crohn's disease went into complete remission after being dosed with the parasite's eggs. The data seemed to support the "hygiene hypothesis," which holds that people have become too clean for their own good. The thinking is that parasites may act on the immune system by boosting the T-cells that help identify and kill infectious agents. When those cells don't work properly, substances and tissues normally present in the body can be mistakenly targeted, causing a range of disorders. "Now that we've eliminated parasites in many Western countries," says Goj, "the immune system doesn't get the required challenge anymore."

Ovamed has supplied sterilized batches of whipworm eggs for human trials for Crohn's disease, multiple sclerosis, peanut allergies, and for symptoms of autism. One of Goj's partners is Asphelia Pharmaceuticals. That San Diego (Calif.)-based company is projecting peak annual sales of about $2 billion in North America for its treatment for Crohn's.

But what about the yuck factor? Will people willingly infect themselves with worms under doctor's orders? Goj, whose company is conducting phase two trials in Crohn's disease at 40 medical centers in Europe, does not anticipate any resistance. "The eggs of the whipworm are so small they're hard to find on a microscope," he says. "All you see is a small cup of water." And since the worms don't reproduce in humans, the parasites are gone in about two weeks.

Whipworms aren't the only invertebrates commanding attention. A 2007 study in Argentina found that MS patients who were infected with Schistosoma mansoni, a parasite found in water supplies in poor countries, suffered fewer relapses than those who were not. An immunologist at the University of Nottingham has been looking into whether pin-sized hookworms may protect against asthma, Crohn's, and MS.

The bottom line: Parasites are being used to treat autoimmune diseases. Some researchers believe people can be too clean for their own good.

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