A study of measles virus and canine distemper virus antibodies, and of childhood infections in multiple sclerosis patients and controls.

We investigated the levels of neutralizing antibodies to measles virus and canine distemper virus (CDV) in 72 multiple sclerosis patients (MS) and matched controls and also examined the frequency and age of onset of a number of childhood illnesses, including measles. The frequency of each childhood illness was not significantly different between cases and controls, but cases did report a later age at measles infection. Our data suggest that the risk of MS is increased by a factor of 1.9 if measles infection occurs between 5 and 9 years of age. A validity survey, based on a questionnaire to general practitioners, suggested substantial inaccuracy in the patients' reports of when they had measles, but the direction and degree of inaccuracy did not appear to be different between cases and controls. We also found higher titres of neutralizing antibodies in cases than controls to both measles virus and CDV, although the CDV difference was not statistically significant. In the light of a significant correlation between measles and CDV titres in both cases and controls, we used paired logistic regression to determine if the case-control difference in titres for each virus could be explained by a confounding effect on one by the other. The numbers were too small, however, to enable us to separate out any independent association of either virus with MS.