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Transmission and Survival of Salmonella Oranienburg in Hens

05/28/2018

Following an egg-borne outbreak of Salmonella Oranienburg (SO) in Midwest states in 2015, researchers at the U.S. FDA Center for Food Safety and Applied Nutrition conducted trials to ascertain whether the pathogen could be vertically transmitted through consuming table eggs.*

 

Twenty-eight week old laying hens were challenged with an oral dose of SO ranging from 107 to 109 CFU and were evaluated over the subsequent four weeks.

 

Although S. Oranienburg was isolated from spleen, liver and the reproductive tract, vertical transmission was a rare observation.  The immune system appeared to inactivate infection after four weeks.

 

The authors concluded that infection with Salmonella Oranienburg did not result in contamination of eggs by the vertical route and that colonization of the ovary and oviduct was of short duration.  Limited survival but not proliferation of the organism in eggs stored at 42F to 46F for weeks is expected.

 

As with studies conducted at the USDA-ARS laboratory in Athens, GA high levels of challenge were used.  Under practical conditions, hens acquiring infection from fomites including mouse droppings in feed would probably ingest 101 to 102 organisms.  Salmonella Oranienburg is a serotype C1 and it is doubtful whether S. Typhimurium mutant vaccine would provide protection.  It is presumed that the hens used in the FDA study were not vaccinated.

 

It can be expected that currently the FDA is repeating the evaluation with S. Braendrup isolated from a North Carolina farm and apparently responsible for 35 cases of salmonellosis associated with egg consumption.  Irrespective of the potential vertical transmission, there is no accepted eradication or NPIP Certification program at the breeder level as with Salmonella Enteritidis. 

 

Obviously effective biosecurity procedures, inclusion of acidifiers in feed where appropriate, feeding all-vegetable diets and rigorous suppression of flies and rodents are appropriate preventive measures. Given that the U.S. industry does not use antibiotics routinely in rearing or in laying flock, the possibility of inducing drug resistance is extremely remote.

 

It is presumed that primary breeders are actively monitoring for the presence of Salmonella, and feeding pasteurized diets to GGP and GP level breeders if not to parents. Breeders and multipliers apply strict preventive measures to interdict exposure to Salmonella which could result in intestinal colonization.

 

*Babu, U.S. et al.(2018) In vivo and in vitro Evaluation of Tissue Colonization and Survival Capacity of Salmonella Oranienburg in Laying Hens. Poultry Science May 25: 1-6 (doi.org/10.3382/ps/pey189)