ARS | Publication request: Fecal shedding and internal organ colonization following exposure of laying hens to different oral doses of Salmonella Enteritidis

Submitted to: Poultry Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2011
Publication Date: July 18, 2011
Citation: Gast, R.K., Guraya, R., Guard, J.Y., Holt, P.S. 2011. Fecal shedding and internal organ colonization following exposure of laying hens to different oral doses of Salmonella Enteritidis. Poultry Science Symposium Proceedings. Poultry Science. (E supplement 1):2.

Technical Abstract: Contaminated eggs produced by infected laying hens continue to pose a significant public health concern as a leading source of transmission of Salmonella Enteritidis infections to humans. A recently implemented national regulatory program for egg-producing flocks in the United States seeks to control egg-borne transmission of illness to consumers via a diverse program of mandatory risk reduction practices plus testing to detect infected flocks. However, many aspects of S. Enteritidis infections in laying hens, including the precise relationship between the magnitude of oral exposure and important infection parameters such as the duration of fecal shedding and the numbers of bacteria that reach internal tissues, remain unresolved. In the present study, groups of laying hens were experimentally infected with oral doses of 104, 106, or 108 cfu of a phage type 13a strain of S. Enteritidis. In one set of trials, fecal shedding was monitored for 8 wk after inoculation. In a second set of trials, the number of S. Enteritidis cells in the livers of infected hens was determined at 5 d and 20 d post-inoculation. At 1 wk post-inoculation, the frequency of fecal shedding of S. Enteritidis ranged from 23.8% for the 104 cfu dose to 87.5% for the 108 cfu dose. Detectable fecal shedding had ceased by 4 wk post-inoculation in the 104 cfu group, but small percentages of the other two inoculated groups were still shedding at 8 wk post-inoculation. After inoculation with 108 cfu, significantly (P < 0.05) greater numbers of S. Enteritidis were isolated from livers at both 5 d and 20 d post-inoculation than for either of the lower doses. These results demonstrate that the oral exposure dose has significant effects on important parameters of S. Enteritidis infection in laying hens which could potentially influence the outcome of testing efforts. Understanding testing results and refining testing protocols requires an understanding of how different levels of exposure are likely to be detected by particular sampling methods.