Horizontal transmission of Salmonella enteritidis and effect of stress on shedding in laying hens.

Horizontal transmission of Salmonella enteritidis in laying hens and the short-term effect of stress on shedding were examined in 32 seven-month-old laying hens. Half were inoculated with 10(5) colony-forming units of S. enteritidis phage type 4, and the remaining half were left uninoculated to study horizontal transmission. Isolation of S. enteritidis from cecal droppings of all hens was attempted every morning. Uninoculated hens rapidly became infected through contaminated drinking water. Introduction of young chickens to the same rearing room and withdrawal of water and feed for 2 days coincided with a rapid increase in the shedding rate of S. enteritidis for a short period of time. The results showed that a short-term increase in the shedding rate of S. enteritidis is associated with short-term exposure to environmental stress.