Contamination of eggs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing.

Authors: Gast, Richard; REGMI, PRAFULLA - North Carolina State University; Guraya, Rupinder - Rupa; Jones, Deana; ANDERSON, KENNETH - North Carolina State University; KARCHER, DARRIN - Purdue University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2019
Publication Date: 9/15/2019
Citation: Gast, R.K., Regmi, P., Guraya, R., Jones, D.R., Anderson, K.E., Karcher, D.M. 2019. Contamination of eggs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing. Poultry Science. 98:5023-5027.

Interpretive Summary: Contaminated eggs produced by infected laying hens can transmit Salmonella Enteritidis to consumers. Eggs become internally contaminated (in the yolk and albumen) because these bacteria are deposited within eggs as they develop inside hens' reproductive tracts. The various available systems of housing for laying hens have been widely discussed in recent years in regard to their animal welfare implications, but their microbiological consequences are not entirely clear. The present study evaluated the production of eggs contaminated with S. Enteritidis by laying hens housed in two different systems. Laying hens from four commercial genetic lines (two that lay white eggs and two that lay brown eggs) were housed in either conventional cages or enriched colonies (which provide access to perches and nesting areas). All hens were experimentally infected with S. Enteritidis and their eggs were collected for several weeks and tested for S . Enteritidis contamination of the internal contents. S. Enteritidis was found more often inside eggs from the two white egg lines than from the brown egg lines in either type of housing. One brown egg line laid fewer contaminated eggs than any other line and the egg contamination frequencies of the two white lines differed significantly. These results demonstrate that S. Enteritidis deposition inside eggs can vary between genetic lines of egg-laying hens, but different housing systems do not appear to influence these trends.

Technical Abstract: Human illness caused by the consumption of eggs contaminated with Salmonella Enteritidis is a continuing international public health concern. This pathogen is deposited inside the edible contents of eggs as a consequence of its ability to colonize reproductive tissues in infected hens. Conditions in the housing environment can influence the persistence and transmission of avian Salmonella infections, but the food safety ramifications of different poultry management systems are not entirely clear. The present study assessed the deposition of Salmonella Enteritidis inside eggs laid by groups of experimentally infected laying hens of four commercial genetic lines (designated as white egg lines W1 and W2 and brown egg lines B1 and B2). Groups of hens from each line were housed at 555 cm2 of floor space per bird in both conventional cages and colony units enriched with access to perches and nesting areas. All hens were orally inoculated with 5.75 × 107 cfu of a two-strain Salmonella Enteritidis mixture, and the internal contents of eggs laid 5-24 d post-inoculation were cultured to detect the pathogen. No significant differences in egg contamination frequencies were found between the two housing systems for any of the hen lines. Contaminated eggs were laid between 7 and 21 d post-inoculation at an overall frequency of 2.47%, ranging from 0.25% to 4.38% for the four hen lines. The frequency of Salmonella Enteritidis recovery from egg samples was significantly (P < 0.05) lower for line B1 than for any of the other lines, and the egg contamination frequency for line W1 was also significantly greater than for line W2. The overall incidence of contamination among white eggs (3.38%) was also significantly higher than among brown eggs (1.56%). These results demonstrate that Salmonella Enteritidis deposition inside eggs can vary between genetic lines of infected laying hens, but housing these hens in two different systems did not affect the production of contaminated eggs.