Multiple sclerosis and dog ownership. A case-control investigation.

In 1977 and 1978 Cook and his associates demonstrated a positive association between ownership of small dogs and both familial and sporadic cases of multiple sclerosis in New Jersey. Because of the far reaching implications of this work, a similar study was carried out and 72 patients with clinically definite multiple sclerosis (MS) who were resident in the area covered by the Oxford Regional Health Authority, were interviewed to ascertain their past exposure to housepets and other animals. Two hospital controls were chosen for each patient matched for age and sex and area of residence, and these were interviewed in the same manner as the MS cases by the same interviewer, usually in the patients' homes. Similar proportions of cases and controls had resided in a household with a dog at some time prior to the onset of their disease and there was no evidence that cases had lived with more dogs or had lived with them for longer periods than had controls. There was no indication that cases had greater exposure than controls to dogs or any other housepet in the early years of their life or in the period immediately prior to disease onset. Our data suggest that exposure to housepets and other domestic animals is unlikely to be an aetiological factor in MS.