Abstract
Outbreaks of abortion associated with infection by Salmonella montevideo have affected sheep in the east, especially the south-east, of Scotland each year since 1972. Disease in the north and north-east was usually less severe. Between 1 January 1970 and 31 December 1981, a total of 67 incidents affecting sheep were reported by veterinary laboratories to the Communicable Diseases (Scotland) Unit, 87% of which presented during the main lambing months of February, March and April. Twenty-one episodes of bovine infection were also recorded over the same period, 17 of which involved single animals only, usually an aborted cow or a scouring calf. Despite intensive investigations, neither the origin nor the mode of spread of S. montevideo infection among sheep and cattle in Scotland have been established with any certainty, although there has been considerable evidence indicating the role of scavenging wild birds, particularly seagulls, as vectors transmitting infection to other farms in the same district. Also largely unexplained are the differences in the epidemiology and clinical pattern of disease in the south-east compared to the north and north-east, while sheep in the west of Scotland have remained virtually unaffected throughout.