Colonization of the chicken reproductive tract and egg contamination by Salmonella

The food-borne salmonellosis pandemic in humans is for a large part caused by the consumption of contaminated eggs. Infection of the reproductive organs of laying hens often is the underlying phenomenon leading to the production of contaminated eggs. To date, the pathogenesis of reproductive tract infection in hens has not received the full attention it merits in relation to its importance in transmitting Salmonella infections within the poultry population and from poultry to man. This review discusses the different possible infection routes leading to egg contamination and emphasizes on the oviduct and ovary colonization in the process of egg contamination. The role of known bacterial virulence factors in the pathogenesis of reproductive tract infection is discussed. Immune responses in the oviduct, related to Salmonella infection, are described. Finally, different possible approaches to protect laying hens against reproductive tract infection by Salmonella are reviewed.