The issue of salmonella in the environment is likely to come to the fore as the upcoming EU salmonella rules will require increasingly stringent sampling regimes for the bug.
One vaccine manufacturer has reassured producers that the use of a live vaccine will not result in a vaccine strain being detectable in the environment.
“Live vaccines administered through the drinking water provide a convenient, welfare-friendly way to build up immunity,” said Eduardo Bernardi, vaccine marketing director for Lohmann Animal Health.
“But because we are dealing with a zoonose, it is important that the live vaccine strains are not found in the environment – for example in faeces or dust – or in other species, such as rodents.”
He explained that important safety features in a live vaccine needed to be considered by egg producers, including the fact that it could be easily differentiated from field strains through routine methods and that it should be excreted for a minimum amount of time after vaccination.
In particular, it should not be excreted when birds were already in production.
Where salmonella-free status is aimed at, no vaccine strain should be detectable in the environment. This was already an essential requirement in many countries for the licensing of live vaccines.
In addition, vaccine strains should not be shed in or on the eggs.
“As a matter of principle, eggs should not contain live salmonella, whether vaccine strain or not, regardless of whether contamination comes via the ovary or through faecal matter on the shell,” declared Mr Bernardi.