Salmonellosis

Diagnostic Approach to Disease Control and Epidemiology in the Bovine Animal

Abstract

Salmonella bacteria have a remarkable ability to survive under adverse conditions. They survive between the pH's of 4 to 8, and can grow between 8 and 45°C. Salmonella are facultative anaerobic bacteria that can survive under low oxygen tension such as in manure slurry pits. Salmonella are known to survive for long periods in soil and in water. Salmonellae spread onto fields in the form of manure may survive for long periods; it is best to spread the manure onto flat land (to prevent runoff problems) where it is exposed to the drying effects of wind, and the bactericidal effect of UV irradiation from the sun; manure should be spread onto cropland rather than onto pastures for grazing. There has been much recent investigation into the advantages of different manure disposal methods; composting has many advantages from the standpoint of controlling disease. Salmonellae, as gram negative rods, are no more or less sensitive to the effects of commonly used disinfectants than are other gram negatives. Chlorine solutions, iodines, quaternary ammoniums, phenolics, etc., are very good at killing salmonellae on surfaces; however, efficient scraping/dry cleaning is important to get rid of organic matter and bedding, followed by wet cleaning with high pressure hot water/steam and then disinfection. The interval between wet cleaning and disinfection must not be too long or salmonellae can "bloom" in the wet environment. Many strains are relatively resistant to the effects of drying, salting, and smoking of foods. However, salmonellae are very sensitive to beta and gamma irradiation.