On a PRRS negative GP farm, a PRRS PCR positive result was detected during regular sampling test. If we do test and slaughter for all herds immediately, will it be possible to return to a PRRS negative status after then?
The elimination of PRRS by what is known as the “Test and Removal” technique was described in 2001 by Scott Dee, who carried it out successfully on chronically infected farms.
In the case of a recent infection, the risk is that by the time you have the results, the virus will have already infected other animals, spreading the infection.
The infection spreads much more rapidly among animals that have never had contact with the virus than among animals that already possess a certain immunity, hence the difficulty of using such a technique at the beginning of the infection.
However, it could be an option in those cases in which the positives are relatively isolated from the rest of the animals and there is also the possibility of having urgent PCR results.
But in any case, consideration should be given to re-testing the status of the pigs that remain, a few days after the removal of the positive’s ones (5-10 days), in order to ensure that the virus has not spread to others.
If what was detected during the routine test is only a positive PCR result, I would remove that animal and retest the rest to verify that there are no more infected animals.
In these cases, it is possible that it is not a real infection, but a work error.
If you want to know more about diagnostic, transmission within herds, and PRRS eradication, read out chapters and publications: “Diagnostic & monitoring” , “Transmission within herds” and “Eradication of PRRS virus in a breeding farm using UNISTRAIN® PRRS vaccination”
Dee et al. An evaluation of test and removal for the elimination of porcine reproductive and respiratory syndrome virus from 5 swine farms. The Canadian Journal of Veterinary Research 2001;65:22-27
Marcovetgrup S.L. – Spain