Do we know for how long the PRRS virus can remain in a syringe?

Dr. Hagen and Dr. Steenaert, of Boehringer Ing., designed a study aimed at seeing how long PRRSv can be detected in syringes previous used for vaccination. This study was presented at the last ESPHM held in Barcelona.

In an endemic PRRSV infected sow herd – 1000 sows and weaners – in periodic PCR monitoring in non PRRS vaccinated piglets PRRSV was shown, ORF5 99% homologous to the vaccine strain used before. Possible infection routes were discussed. A persistent PRRS-MLV contamination of bottle feed syringes - that were repeatedly used for piglet vaccination - could not be excluded.

The goal of the study was to find evidence for PRRS-MLV persistency in the materials used for
vaccination.

Two bottle feed syringes that were previously used in the farm and two new bottle feed syringes were prepared, by using them with freshly reconstituted PRRS-MLV.
After use all syringes were cleaned externally, rinsed with tap water (10 strokes) and stored at 3-8^oC, copying the standard procedures in the farm.
The syringes were sampled: using vaccine (T0-V) and again by using sterile water at different times :

                         - Immediately after rinsing (T0-R)

                         -  At 1 week  (T1)

                         -  At 3 weeks (T3) of storage.

The samples were individually tested by PRRS PCR and ct values were compared.

At T0-V all ct values were 18. At T0-R ct values ranged from 32-35. At T1 ct values were 34 and 37.
At T3 ct values ranged from 30-34.

With these results, the farm changed its internal biosecurity protocols, and started using new syringes in every batch. 

PRRSV can survive for 11 days when in a moist/ wet and cold environment. These conditions were met in the farm.

The PRRS PCR positive test results of materials up to 3 weeks after use with PRRS MLV serve as proof of concept for a possible infection route. One may question if this is still viable PRRSV.