Stabilization of PRRSv Circulation Following Implementation of Mixed PRRSv Vaccine Program18 September 2015
PRRS is one of the most significant pig diseases. Current vaccination strategies are based on the use of MLV (Modified Live Vaccines) or KV (Killed Vaccines). This case report describes the stabilization of PRRSv circulation in a nursery and fattening unit, after the introduction of a PRRSv vaccination at day 90 of gestation with a KV vaccine in breeders vaccinated at day 6 of lactation with a MLV-EU type vaccine, write L. Willems et al, Merial.
The field study was carried out in a 400-sow PRRSv-positive farrow-to-finish farm operating in 5 batches of 80 sows in Brittany, France. During lactation, vaccination against PRRSv (MLV) is performed.
No clinical signs are observed in the maternity unit.
Piglets are vaccinated against M.hyopneumoniae. During the nursery and fattening period, respiratory symptoms are common and antibacterial treatments were frequently performed against PRDC.
In December 2013, PRRSv infection was confirmed in two batches in the nursery, by positive results of both PCR and ELISA (IDEXX) on sera and oral fluids.
In January 2014, one batch of breeders received a second PRRSv vaccination at day 90 of gestation with a KV (PROGRESSIS®, Merial). A cohort of 10 piglets born from these sows were monitored for the detection of PRRSv infection (PCR on oral fluids) and serologic profiling (ELISA) at 8, 12 and 16 weeks of age.
The offspring of the vaccinated sows did not show any respiratory symptoms until slaughter. All except one (S/P ratio 0,66 at 8 weeks of age) ELISA results at 8 and 12 weeks of age were negative. Delayed PRRSv circulation was shown by positive results on both sera and oral fluid samples at 16 weeks of age.
In February 2014, while sows were vaccinated according to the historical vaccination protocol (only at day 6 in lactation with the MLV vaccine), respiratory symptoms reoccured in the nursery, suggesting an early PRRSv infection. In June 2014, the KV vaccination at 90 days of gestation was introduced as a routine practice. In October 2014, a transversal oral fluid sampling showed the persistence of maternal antibodies until 10 weeks of age, and the absence of PRRSv circulation until 12 weeks of age.
Under the field conditions of the study, the implementation of mixed PRRSv vaccination program in sows combining MLV vaccination at day 6 of lactation and PROGRESSIS vaccination at 90 days of gestation resulted in a delayed PRRSv circulation, as well as a clear reduction of associated clinical signs.
These results indicates that the use of PROGRESSIS 3 weeks before farrowing can be an efficient tool for the control of early virus circulation in piglets and total herd stabilization.
Presented at the 2015 European Symposium of Porcine Health Management