Some aspects of the epidemiology and control of Salmonella typhimurium infection in outwintered suckler cows.

Two outbreaks of Salmonella typhimurium infections affected outwintered, spring-calving suckler cows in late pregnancy. The infections spread rapidly both within and between groups of stock on the affected farms, with morbidity in the infected groups varying from 14.5 per cent to over 60 per cent, and mortality in adult cattle varying from 0 to 14.3 per cent. Prophylactic measures included the use of antibiotics and killed vaccines against Escherichia coli, Salmonella dublin, S typhimurium, and Pasteurella multocida. In one outbreak, use was also made of a polyvalent serovaccine and hyperimmune serum against E coli, S typhimurium, and S dublin. In both outbreaks no new cases were reported in the affected groups after the administration of the second dose of vaccine, and there was no resurgence of disease on the affected farms within 18 months of the primary outbreaks.