ARS | Publication request: ASSESSING THE SENSITIVITY OF EGG YOLK ANTIBODY TESTING FOR DETECTING SALMONELLA ENTERITIDIS INFECTIONS IN LAYING HENS

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 10, 1997
Publication Date: N/A

Interpretive Summary: Salmonella enteritidis (SE) contamination of eggs is a significant cause of human illness. Testing to detect SE infections in laying hens is an important component in efforts to reduce the likelihood that contaminated eggs will reach consumers. In such testing programs, a preliminary screening test is usually applied to select flocks for subsequent confirmatory testing. Testing for antibodies in egg yolks has previously been shown to effectively predict the probability of egg contamination, but the sensitivity of this type of screening test has not been established. In the present study, hens were experimentally infected with different numbers of SE and eggs were collected for yolk antibody testing using an enzyme immunoassay. All hens inoculated with a very large dose of SE were detected as infected by testing for yolk antibodies, as were 35% of hens inoculated with only about 1000 SE. Antibodies could also be detected after dilution to simulate the pooling together of up to 10 eggs Egg yolk antibody testing thus allows rapid and sensitive screening of individual or pooled samples to identify SE-infected flocks.

Technical Abstract: To assess the sensitivity with which testing for specific egg yolk antibodies detects Salmonella enteritidis (SE) infection in egg-laying chickens, groups of hens were orally inoculated with either 1000, 100,000 or 10,000,000 cfu of SE. Eggs from these hens were collected for 4 weeks after inoculation and tested for antibodies to SE flagella by ELISA. All hens that were inoculated with 10,000,000 cfu of SE were detected as infected by the egg yolk ELISA, as were up to 66% and 35% of hens inoculated with 100,000 or 1000 cfu, respectively. Even when yolks from infected hens were diluted 1:10 in yolk from uninfected hens, specific antibodies could still be found in eggs from as many as 31% of hens given 10,000,000 cfu of SE and 13% of hens given 1000 cfu.