Another close relative to the measles virus, Distemper in dogs, is a nervous system disease. This and a lot of other information has lead many to suspect that MS is caused by measles virus or a close relative. This information has been around for decades and yet nothing productive has come from it. We now know that a retrovirus cousin of the HIV causes an MS-like illness. Lyme disease, caused by a spirochete, is pathologically similar to MS in some ways.
Scientists study disease using animal models.
There is a number of virus animal models for MS but the best is a disease called EAE, experimental allergic encephalomyelitis. When Louis Pasteur made the original rabies vaccine, he used virus infected rabbit nervous tissue which contained myelin. This sensitized a few subjects who developed a fulminent autoimmune nervous system disease. Animals injected with CNS myelin develop the same disease. No virus is involved.