Field experiences with concurrent vaccination strategy aiming to control breeding performance in PRRS in large pig farms

PRRS virus was identified in 1990' earlier and classified two groups in type 1 and type 2 genetically. PRRS virus has been discovered all over the world. PRRS modified live virus vaccines are introduced in many country to control PRRS. But these PRRS live virus vaccines didn’t defend against heterologous PRRS virus perfectly. This field case shows reproductive performance after type 1 modified live virus vaccination when it is infected with type 1 wild PRRS virus and its symptoms are severe while using type 2 modified live virus vaccine in a large farm.

This farms are separated in five reproductive farm independently (530, 980, 930, 930, 940 sows) in identical area. Each farm was already identified type 2 PRRS virus about 18% different from VR-2332 ORF5 sequence and have type 2 modified live vaccination to sows quarterly to control PRRS strategically(MLV, 2.0ml) . Type 1 wild PRRS virus was identified in Dec 2013. And in Jan 2014 type 1 modified live virus vaccine(Amervac, 2.0ml) was introduced. In 2014 type 1 and type 2 modified live virus vaccines(each vaccination 2.0ml) are concurrently used quarterly(in 2014 total PRRS modified live vaccination 10 times) and type 2 modified live vaccine were introduced in 3 weeks weaning piglets continuously. Serum samples were tested using PRRSV ELISA and RT-PCR was performed from blood samples before quarterly PRRS modified live virus vaccination Blood samples in sows 10, nursgery piglets 10, 40dys piglets 10 , 70dys piglets 10 and replacement gilts 10 are collected from each five farm.

A year later after concurrent vaccination with MLV(2.0ml) and AMERVAC(2.0ml) no wild type PRRS virus was detected in the sera of the sows and replacement gilts but type 1 PRRSV or type 2 PRRSV are still detected in the sera of the nursery piglets, 40days pigs, 70days pigs But the performance of reproduction are significantly improved in 2014 compared with 2013 In 2013 total 616 sows in all five pig farms are aborted with infection of PRRSV In 2014 total 208 sows are aborted. And total mortality rate has reached 11.7% in 2013, but total mortality rate have decreased by 0.7% in 2014

Large-scale five farms are concentrated in identical areas and it is difficult to maintain biosecurity of these farms and prevent PRRSV infection outside. Despite of detecting PRRSV in piglets, 40days and 70days concurrent type 1 and type 2 PRRSV vaccination has enhanced breeding performance especially about 400 sows without abortion have contributed to increase production volume in farms.

Disclosure of Interest: None Declared.