A couple of months ago, my daughter's school sent home a letter saying that a child in her class had been found to have pinworms. While this caused mass panic among the parents, my mother-in-law shrugged and said, "When I was growing up, everybody had pinworms at some point during childhood, often many times. People worry too much about these things now." Little did she know that she was touching on an emerging topic in MS, known as the "hygiene hypothesis."
The idea behind the hygiene hypothesis is that certain infections or other exposures may prevent autoimmune disease activity by keeping the immune system busy with foreign invaders and less likely to turn on itself. MS is thought to be an autoimmune disease, with certain immune cells attacking the myelin sheath surrounding the nerves. The symptoms of multiple sclerosis are caused by this damage to the myelin.
Some experts point to the hygiene hypothesis as a possible explanation as to why MS is more prevalent in the US, Canada and Europe than it is in other countries, where people are more likely to be infected with parasites (and thus "protected," according to the theory). It could be that those of us in the countries with highest MS prevalence are growing up and living in an environment that is too "clean" in that it doesn't provide enough challenges to our immune systems.
The data seem to support the hygiene hypothesis theory. At ECTRIMS 2011, Jorge Correale of the Raúl Carrea Institute for Neurological Research in Buenos Aires presented fascinating data that demonstrates that infection with parasites seems to protect people with MS from disease activity.
In an earlier study, Correale's team followed 24 people with MS for over four years - half of whom had become infected with a variety of intestinal parasites (worms called "helminths") after they were diagnosed with MS, but before they were recruited into the study.
The results were amazing. Infected people had a relapse rate that was almost 19 times lower than in uninfected people over the course of the study – 4 relapses in the infected people, compared to 56 in the uninfected people. In addition, the people with parasites had lower disability (as measured by EDSS score) and fewer lesions.
Today, Dr. Correale reported that after 5 years, 4 of the 12 infected people began to show negative symptoms of being infected with these parasites, such as diarrhea and abdominal pain. These people were treated with anti-parasite drugs to kill the helminths and followed for an additional 2 years.
When the parasites were gone in these 4 people, MS disease activity increased. People began having relapses and new lesions were seen on MRI scans.
When the researchers examined the blood of these patients, they saw that within 3 months of killing their parasites, certain immune cells that stimulate the immune system (causing inflammation) were increased, while there was a decrease in anti-inflammatory cells.
So, what do we do with this information? Clearly, no one is urging people with MS to try and find some random parasite eggs to ingest. However, this is being pursued in a research setting in the US. Dr. John Fleming's group at the University of Wisconsin is currently recruiting patients for a study called, "Helminth-induced Immunomodulation Therapy (HINT) in Relapsing-Remitting Multiple Sclerosis," where participants will be given a drink containing harmless whipworm eggs and followed for a period of time. Hear more from Dr. Fleming on today's "Daily Minute" video.