Horizontal transmission of Salmonella enteritidis in molted and unmolted laying chickens

The impact of induced molting on the horizontal transmission of S. enteritidis was studied. In Expt. 1, every other hen in rows of either molted or unmolted hens was infected with S. enteritidis (1 x 10(6) bacteria/hen). S. enteritidis was transmitted more rapidly to the unchallenged hens in the adjacent cages of molted hens than in unmolted hens, and these molted hens shed significantly more of the organism than unmolted hens. In Expts. 2 and 3, the center hen in two rows each of 11 molted and unmolted hens was infected with S. enteritidis (dose of 6-8 x 10(4) in Expt. 2 and 1 x 10(3) in Expt. 3). In both trials of Expt. 2, the rate of transmission was significantly higher in molted hens than in unmolted hens, and the molted hens shed significantly more of the organism. In Trial 1 of Expt. 3, molting had little effect on S. enteritidis shedding. In Trial 2 of Expt. 3, however, molted hens had significantly higher shed rates and shed more S. enteritidis than the unmolted hens. Individual hens in Expts. 2 and 3 frequently shed more S. enteritidis than the original challenge. The amplification of intestinal S. enteritidis in the molted hens plus their previously described higher susceptibility to S. enteritidis infection accelerated transmission of the organism to the uninfected hens in neighboring cages. These results indicate that induced molting can have substantial effects on transmission of S. enteritidis to uninfected hens, which could affect the overall S. enteritidis status of a flock.