CHARACTERISTICS OF SALMONELLA ENTERITIDIS CONTAMINATION IN EGGS AFTER ORAL, AEROSOL, AND INTRAVENOUS INOCULATION OF LAYING HENS

Authors: Gast, Richard; Holt, Peter

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2002
Publication Date: 9/24/2002
Citation: Gast, R.K., Holt, P.S. 2002. Characteristics of salmonella enteritidis contamination in eggs after oral, aerosol, and intravenous inoculation of laying hens. Avian Diseases.

Interpretive Summary: Experimental infection models are useful for understanding how Salmonella enteritidis (SE) is deposited in eggs and for testing potential strategies to control egg-borne transmission of disease to humans. Oral inoculation of laying hens most closely simulates naturally occurring infections, but alternatives such as intravenous and aerosol inoculation have also been recommended. The present study compared the frequency, level, and location of SE deposition in egg contents during the first 21 days following experimental inoculation by three different routes (oral, aerosol, and intravenous). All three routes of inoculation led to similarly low overall frequencies of production of internally contaminated eggs and all three routes of inoculation yielded yolk contamination more often than albumen contamination. The number of SE cells found in contaminated eggs was generally low, although intravenous inoculation led to higher levels of SE deposition in yolks than the other routes. Overall, neither aerosol nor intravenous inoculation offered any clear advantages over oral inoculation for the experimental simulation of naturally occurring SE contamination of eggs.

Technical Abstract: The present study compared the frequency, level, and location of Salmonella enteritidis (SE) deposition in egg contents following experimental inoculation by three different routes. Groups of hens received either an oral, aerosol, or an intravenous dose of SE. Eggs laid during the first 21 days postinoculation were cultured to detect and enumerate SE in the yolk and albumen. No significant differences were observed between the three inoculation routes in the frequencies of isolation of SE from either yolk or albumen. For all three routes of administration, SE was recovered more often from yolk (at frequencies ranging from 4% to 7%) than from albumen (0% to 2%). Over 73% of contaminated eggs harbored fewer than 1 CFU of SE per ml and only 3% of such eggs contained more than 100 CFU/ml. Significantly higher levels of SE contaminants were associated with intravenous inoculation than with the other routes. No advantages of using aerosol or intravenous administration of SE as alternatives to oral inoculation for inducing the production of contaminated eggs were evident in this study.