Multiple sclerosis unrelated to dog exposure.

We conducted a case-control study to evaluate the possible association between exposure to dogs and MS. Seventy cases were compared with 70 age- and sex-matched neighborhood controls and 57 cases with 57 age- and sex-matched clinic controls. No association was found, by age groups or by time periods before onset of MS, between MS and presence of any dog, a small dog, a medium or large dog, or an indoor dog in the household. There was a significant negative association between MS and presence of cats in the household and MS and presence of medium and large dogs in the household, and a significant positive association, for several age groups and time periods, between MS and a history of canine distemper in a household dog. The basis for these significant associations is not clear. This study adds weight to the evidence against an association between exposure to small or indoor dogs and MS.