Jim Turk initially put his symptoms down to stress. The self-described "health nut" who was in training to run marathons suddenly found himself unable to jog for more than a couple of minutes before coming to a gasping, staggering halt. His speech began to slur. Turk, then in his early thirties, blamed the combined pressures of juggling a full-time job, studying for a master's degree and his parenting responsibilities. When he collapsed in the middle of a baseball field one sunny afternoon in 2008 while coaching his son’s team, he realised it was time to seek help.
At the hospital, magnetic resonance imaging (MRI) scans revealed plaques peppered throughout Turk’s brain and spine. The diagnosis was obvious: multiple sclerosis, the autoimmune condition in which the body eats away at its own nerve cell casings. The cure: not known yet.
A month later, Turk saw an ad on the news seeking multiple sclerosis patients to try out an unusual new treatment at the University of Wisconsin, in his hometown of Madison. Patients were being asked to infect themselves with live pig whipworm eggs to see if the parasites alleviated any of their symptoms or slowed the spread of telltale brain and spine lesions. “I’ve always had a research interest so I decided to put my money where my mouth is,” Turk says. “Plus I was terrified and didn’t know what to do.”
When Turk arrived at the clinic, John Fleming, a professor of neurology, presented him with a vial of clear liquid. “It tasted a little bit salty but otherwise it was just water," says Turk. "I couldn’t see the eggs or anything.”
For the next three months, he and four others visited the lab every two weeks to swallow doses of 2,500 parasite eggs. At the start of the trial, MRI scans showed patients had an average of 6.6 active lesions – scars on the protective layer around nerve cells that disrupt the transmission of electrical messages in the brain and spinal cord. By the end of the study, that number had dropped to two. Two months after discontinuing the worm treatment, the lesions rebounded to an average of 5.8. “The beauty of this is that the number of new lesions is really an objective, brutally honest answer,” Fleming says. “It’s not proof, it’s not definitive, but at least it’s promising.”
Fleming’s trial in 2008 was the first to infect multiple sclerosis patients with live parasitic worms, also known as helminths, but others were also investigating their therapeutic potential. The field has its origins in the early 1990s. Joel Weinstock, now chief of the division of gastroenterology/hepatology at Tufts Medical Center in Boston, struck upon the idea during a six-hour delay on the runway at Chicago’s O’Hare airport.
“Over the years, people had looked for environmental factors that caused inflammatory bowel disease and hadn’t found anything,” Weinstock says. “While on the plane, I decided to play a game and pretend that it’s caused by the loss of something rather than the addition of something.” It was as if “a light suddenly went off”, Weinstock says, as parasites came to mind. Hygiene does wonderful things, he realised, but there’s always a price for change.
The price might be the surge in cases of asthma and allergies we’ve seen in western countries over the past 40 years. Likewise, rates of autoimmune and immunoregulatory conditions such as Crohn’s diseases, type 1 diabetes, inflammatory bowel disease and multiple sclerosis have been on the rise. Yet in developing countries, such conditions remain rare.