Salmonella: The chickens and the eggs

Abstract

While poultry meat remains a major vehicle for human salmonella infections, epidemiologic data indicate that the current increase in outbreaks of SE arises from an important new source—intact shell eggs. Studies in the U.S. and U.K. have documented the ability of SE to cause invasive disease in young and old hens (i.e., infection of ovaries, oviducts, and peritoneum that allow for transovarian infection of the developing ovum prior to shell deposition). The persistence of the disease in chickens, and the immune response to various serotypes of SE are unknown and need to be addressed as better test procedures for identifying infected flocks and eggs are designed. Given the probable low minimal infective dose, and the ability of the organism to survive and grow in intact eggs and to survive various cooking procedures, care must be taken in storing and preparing eggs and foods containing eggs. In hospitals, nursing homes, and restaurants, particular care should be taken to reduce the risk of exposure by using pasteurized egg products. The costs of preventing salmonellosis are not known but the cost of a single hospital-based outbreak (involving 242 people and 3 deaths) was estimated to be between $340,000 and $1,530,000 at 1985 prices (31). In order to control the rise in SE and eradicate SE from broiler and layer flocks, the basis for the differences in virulence among SE phage types needs to be identified. Such basic information will provide the foundation for specific identification of flocks infected with epidemiologically important strains, and permit the design of suitable systems for intervention and control.