Internal Organ Colonization by Enteritidis in Layer Pullets Infected at Two Different Ages During Rearing in Cage-Free Housing.

The poultry-housing environment plays a significant role in the transmission and persistence of the egg-associated pathogen Enteritidis in laying flocks. The commercial egg industry is in the midst of a transition toward cage-free housing, but the food safety ramifications of this shift are not yet certain. The present study assessed internal organ colonization by Enteritidis in layer pullets reared in cage-free housing and infected at two different ages. Groups of 280 pullets were transferred from the rearing facility (at 9 wk of age in one trial and 15 wk in another) to a containment facility with four isolation rooms simulating commercial cage-free barns with perches and nest boxes (70 birds/room). Twenty-four pullets in each room were orally inoculated with Enteritidis immediately after placement in the containment facility. At 1-2 wk postinoculation in each trial, samples of liver, spleen, and intestinal tract were collected from all birds in two rooms for bacteriologic culturing to detect Enteritidis. At 21-22 wk of age, samples of spleen, ovary, and intestinal tract were similarly collected and tested from all birds in the remaining two rooms. Among samples collected at 1-2 wk postinoculation, Enteritidis was isolated significantly more often from groups of pullets infected initially at 15 wk of age than from those infected at 9 wk (61% . 38% of livers, 59% . 31% of spleens, and 84% . 57% of intestines). Among samples collected at 21-22 wk of age, the frequency of recovery of Enteritidis was again significantly greater in birds infected at 15 wk of age than in those infected at 9 wk (16% . 6% of spleens, 9% . 1% of ovaries, and 26% . 10% of intestines). These data suggest that Enteritidis infections introduced into flocks during the later stages of pullet rearing have greater potential to persist into the early phase of egg production.