Institution: USDA, ARS
Principal Investigator:
Shawn Bearson
USDA, ARS
1920 Dayton Ave
Ames, IA 50010
A recent foodborne outbreak of Salmonella enterica serovar Reading revealed the need for effective control of this serovar in turkey production. Vaccination can reduce Salmonella in poultry, and this study assessed the vaccine efficacy of two live-attenuated Salmonella vaccines, the commercial AviPro® Megan® Egg vaccine and an internally developed cross-protective BBS 866 DIVA vaccine, to reduce S. Reading colonization in turkeys.
Two vaccination delivery methods were used for both vaccines: oral gavage for administration of primary and booster vaccinations as well as a vaccination regimen with a primary aerosol and water-delivered booster. Compared to non-vaccinated turkeys, all vaccinated groups had 10-1000 times less S. Reading in the cecal tonsils and cecal contents at 1-2 weeks after S. Reading challenge. Dissemination of S. Reading to the spleen was significantly decreased in three of four vaccinated groups at 1 week after S. Reading challenge and trended towards reduction in the fourth vaccination group. Significant reduction was not observed in the cloaca samples, probably due to the small number of Salmonella positive samples from this tissue. Salmonella was infrequently isolated from skin samples. Lastly, four significant contrasts in the dataset suggested that oral gavage may be more effective than vaccination by the aerosol/water combination that was used, likely due to the consistency of vaccine delivery by the oral gavage method.
As neither a single turkey product nor a common supplier of turkey products was identified as the source of the outbreak, it has been proposed that the rapid and uniform introduction and transmission of this emergent S. Reading outbreak strain occurred vertically in commercial turkey production. Thus, the turkey industry would benefit from cross-protective intervention strategies to control emerging Salmonella outbreak isolates to reduce the burden of human illness and industry costs due to product recalls and plant closures. In this study, vaccination with BBS 866 or AviPro® Megan® Egg (both serotype Typhimurium backbone vaccines) significantly reduced colonization by S. Reading in turkeys, indicating that these vaccines are cross-protective and could be a pre-harvest intervention strategy against this serovar. This would thereby potentially reduce Salmonella carriage into the human food chain, limit foodborne outbreaks, diminish the cost of meat product recalls to the industry, and provide the public with a safer food supply.
