Dr. Harry Snelson-American Association of Swine Veterinarians:
We were very concerned about last winter and how that was going to play out and I think that immunity played into that significant outbreak that we saw in 2014, the low levels of immunity.
Now we've built up herd immunity but we've also had a fairly high rate of turn over in the sow herds.
Whether or not that immunity persists to a high enough degree to continue to provide protection, we'll have to see.
Unfortunately the vaccines don't seem to be quite as good at stimulating immunity in naive animals so we still rely pretty heavily on exposure and boosting immunity utilizing vaccines.
So, as the herd is turned over and the immunity levels decline in the breeding herds, we'll just have to see how much virus is still out there, active and spreading and how protected the herds are from an immunity standpoint.
Dr. Snelson notes the virus survives better in cooler weather, herd immunity may be declining and the virus is still out there.
He says the industry has done a good job in responding to this outbreak and he encourages continued emphasis on biosecurity.
Source: Farmscape