Live vaccines cause false alarms

A series of salmonella test false alarms have been triggered following the use of live vaccines on pullet rearing units.

In each case Lion code tests carried out prior to the birds leaving the rearing farm have shown up positive. This has caused the movements of some flocks to be ¡¥frozen¡¦ by officials and caused major headaches for rearers and their customers. But in each case further investigations have shown that a false alarm has been caused because the test has simply shown up the presence of a live vaccine.

Now the Food and Environmental Safety Department of the Veterinary Laboratory Agency has issued guidance on how to prevent the mix-ups. The Agency says the problem is being caused because the live Salmonella Enteritidis vaccine can survive for days both in the birds vaccinated and on surfaces, on litter and elsewhere. It is even possible for a test to prove positive if it is carried out by a stockperson who has vaccinated another flock in recent days.

The VLA says: ¡§It is important to handle the vaccine and take samples in a way which reduces the risk of cross-contamination.¡¨ It lists necessary precautions as:

„« Do not take Salmonella monitoring samples from flocks within two weeks of giving a live vaccine.

„« Wear protective gloves when vaccinating and thoroughly wash and disinfect hands after administering it.

„« If vaccinating and taking tests on the same day always take the tests before handling the vaccine.

„« If positive samples are obtained from any flock make sure that the VLA is informed of the type of vaccine and the administration date when the sample is submitted for serotyping so that additional testing to identify vaccine strains can begin more quickly.

One BFREPA member who had a flock of incoming pullets hit by a false alarm said: ¡§It was a nightmare. We were told the birds had come up positive and for a week we did not know whether we were going to get them or not.

¡§Of course the chances of finding replacement birds would have been very slim. In the end the results were linked to the vaccine and we were given the all clear.¡¨

And a pullet supplier caught in another incident told the Ranger: ¡§What a panic. I can see all the advantages of using live vaccines because the birds do not have to be caught and so on but following this incident I never plan to use the same product again.¡¨