Location: Egg Safety & Quality ResearchTitle: Hypothesis: A role for the mouse as an amplifier of Salmonella enterica on-farm Author
Submitted to: Poultry Science Association
Publication Type: Proceedings
Publication Acceptance Date: 3/14/2011
Publication Date: 7/16/2011
Citation: Guard, J.Y., Sanchez-Ingunza, R., Ahmer, B., Mcclelland, M., Henzler, D. 2011. Hypothesis: A role for the mouse as an amplifier of Salmonella enterica on-farm. Poultry Science Association, July 16, 2011, St. Louis, Mo. p.24. Interpretive Summary:
Technical Abstract: The presence of the mouse in the environment of the hen has been consistently identified as a risk factor for the contamination of eggs by Salmonella enterica serovar Enteritidis (SE). To address how much risk the mouse poses for egg contamination, the spleens and intestines of mice caught on-farm from January 1999 to July 2002 were cultured for recovery of Salmonellae. Of the 933 mice that were caught in 42 hen houses, 1 of every 2.2 houses (45.2%) was positive for SE. More mice were recently collected in winter of 2010 from 15 houses spanning two states. These houses had not been reported as having problems with egg contamination. One (1) of 15 houses (6.7%) yielded one positive mouse of 31 total sampled. The positive mouse came from a house that had been already been identified by the producer as needing more aggressive rodent control, because it had been noticed that mice seemed to be increasing in the house. It was one of 11 captured and none of the other 14 houses yielded more than 3 mice during the capture period. Finally, an additional molecular biology experiment was conducted to see if chickens and mice had different patterns of infection. To do this, chickens and mice were experimentally infected with a library of mutants to compare the ability of each host to overcome founder population effects following oral infection with Salmonella enterica. This approach evaluates if statistically significant replication occurs post-exposure within a given host. Founder populations were surpassed within the mouse, but not in the chicken. Although the difficulties in comparing infection dynamics across time and across genera is admitted, evidence supports the hypothesis that the mouse, in contrast to the chicken, is a vector of amplification for Salmonella enterica on-farm. In addition, sampling of mice in two time frames nearly a decade apart provides some guidance as to how badly mice could contribute to the risk of egg contamination. Approaching the mouse as a vector that poses especially high risk for egg contamination facilitates improving the safety of eggs by guiding allocation of resources and application of best practices.