Multiple sclerosis and distemper in Iceland 1966-1978.

A highly restricted epidemic of canine distemper occurred in southwest Iceland in 1966-67. We have determined the extent of dog contact and exposure to dogs during the distemper epidemic in Icelandic MS patients with onset since 1966. Further, age of onset, and annual incidence of MS from 1966 through 1978 have been determined. Thirty-five of 36 MS patients had close dog contact prior to onset of their illness, and 34 were in the area of the distemper epidemic during 1966-67. A significant decrease in age of onset of MS (31.6 to 26.5) from 1956-1965 to 1967-1978 was noted, consistent with exposure of a susceptible cohort to a point infection with a varible incubation period. A review of incidence of MS in the 10-year periods after distemper epidemics in Iceland in 1921-1922, and 1941-1942 reveal significantly more MS than in comparable time periods before these epidemics. These collective findings are consistent with, but do not prove, a relationship between dogs, distemper and MS.