 Studies have shown that there may be an inverse relationship between infections with worms including hookworms and inflammatory diseases including multiple sclerosis MS. This has been explained by a protective immune reaction that is triggered by the hookworm in the body that dampens inflammation. In mice with MS, infections with some mouse worms reduced the inflammation and damage to their brain. The primary purpose of this study is to determine whether people with MS who are exposed to a small number of hookworms will develop this protective immune reaction that may reduce MS disease activity. We also plan to determine the effect of the hookworms on relapses during 1 year study. 