A possible association between house pets and multiple sclerosis.

29 patients with multiple sclerosis (M.S.) from families in New Jersey believed to have more than 1 member with this disease and 29 controls matched for age, sex, neighbourhood, and socio-economic status were questioned about their ownership of pets. No difference in ownership of cats or dogs was found. Exposure to small indoor pets (cats or dogs), however, was significantly higher in the M.S. group (P less than 0-001). Exposure to small indoor pets was particularly striking during the ten years before onset of initial symptoms of M.S. when the M.S. group was compared to the control group (P less than 0.01). 33 of 49 M.S. patients in these families had a cat or dog in the house within one year before onset of the first neurological symptom. 3 families had more than 1 member in whom initial symptoms of M.S. developed in the same year despite wide age ranges. These results suggest that exposure to house pets may sometimes be associated with subsequent M.S. Our findings should be interpreted with caution until they are confirmed by others.