Occurrence of Salmonella enteritidis in the U.S. commercial egg industry: report on a national spent hen survey.

In order to estimate the prevalence and distribution of Salmonella enteritidis in U.S. commercial egg-production flocks, a survey of spent laying hens was conducted over a 3-month period. Seven of the 10 largest spent-hen processing plants in the United States participated. Ceca were sampled twice weekly from birds presented for slaughter at these plants. Samples were cultured for Salmonella and S. enteritidis, and S. enteritidis isolates were phage-typed. Overall, 23,431 pooled cecal samples were collected from a total of 406 layer houses. Salmonella (any serotype) and S. enteritidis were recovered from 24% and 3% of the pooled samples, respectively. The distribution of S. enteritidis phage types was consistent with data reported by others. Regionally, the estimated prevalence of S. enteritidis-positive houses (i.e., at least one positive sample found in a house) for the Northern, Southeastern, and Central/Western regions was 45%, 3%, and 17%, respectively. Overall, the prevalence of Salmonella-positive houses was 86%.