Preconvention Seminar 7: Dairy Herd Problem Investigation Strategies AMERICAN ASSOCIATION OF BOVINE PRACTITIONERS 36 th Annual Conference, September 15-17, 2003 - Columbus, OH Salmonellosis in Cattle: A Review Drs. Sheila M. McGuirk and Simon Peek School of Veterinary Medicine, UW-Madison Salmonella spp. infection occurs when a susceptible animal ingests the bacteria. Dairy cattle ingest feed or water that has been contaminated with feces from animals shedding the organism. Salmonellosis has a wide spectrum of manifestations in cattle. Asymptomatic, mild clinical or fulminant bacteremia/septicemia and endotoxemic infections can occur. The manifestations vary with virulence of the strain, infectious dose, and immunity of the host. On many dairies, salmonellosis is an opportunistic infection. Where Does It Come From? On a dairy, the source of the infection is usually feces from infected cows. It may be difficult to tell which cows are shedding bacteria because asymptomatic and subclinically affected cows can shed as many organisms in their manure as the cows that are sick with salmonellosis. Other sources of infection may be rodents, birds (including waterfowl), flies, feral cats, dogs, raccoons and, rarely, people. ♦ Fecal – oral transmission ♦ Aerosol transmission – in confinement facilities ♦ Saliva and nasal secretions – especially in shared waterers ♦ Milk and colostrum Why Doesn’t It Run Its Course and End? Salmonella outbreaks commonly last several months. Protracted problems can be the result of a number of factors – persistence in the environment, persistence of risk factors, carrier state or prolonged shedding, or reinfection of susceptible animals. On some dairies, particularly those with large numbers of cattle, the disease may become endemic. ♦ Reservoirs University of Wisconsin, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706