Carthage vets focusing on ‘regional’ IAV-S vaccination strategies for breeding herds

As influenza viruses evolve, is there a more effective way to manage vaccinations for influenza A virus in swine?

Clayton Johnson, DVM, and his colleagues at Carthage Veterinary Service, believes there is – “especially as we have better diagnostics and information becoming available,” he told Pig Health Today.

IAV-S vaccination strategies have historically focused on the pre-farrowing timeframe to benefit piglets. But Johnson supports moving vaccination earlier into the breeding herd to better protect gilts and gestating sows and then develop different strategies to protect the individual piglet. Whole-herd vaccination for IAV-S is a more common consideration today.

For the breeding herd, the Carthage veterinarians are applying a regional strategy to IAV-S vaccination, not unlike the approach taken for porcine reproductive and respiratory syndrome (PRRS). “Region is a very broad term, it could be a state, county or neighborhood,” he explained. “It’s really focusing on a population of pigs that we think are likely to share influenza viruses and what’s circulating in your region.”

Two drivers

Two factors driving the Carthage approach:

1) “Our clients expect us to produce a weaned pig that is the right weight and that is not coughing,” Johnson noted. “And IAV-S complicates both of those things.”

2) Consistently producing the right number of quality pigs. “If a sow has an issue with IAV-S, it causes her to not become pregnant or to lose a litter or not consume enough feed and produce low-birth-weight pigs,” he added.

So, the first step is to define the region; next is to characterize the influenza strains circulating in that region. Sequencing viruses is an automatic request for Carthage Veterinary Service when sending samples into the diagnostic lab.

“I can compare that sequence from one strain to another or one isolate or one case to another,” Johnson said. “I can compare and look at clusters or families. It gives us a ball park perspective – ‘Is this something I’ve seen before or is it something new and different?’”

Then he delves further into diagnostics to determine vaccination strategies. “Do we use a commercial or autogenous vaccine? How do I select the antigens that go into that vaccine to provide the greatest cross-protection?” he asked.

Mass vaccination

The strategy then is to conduct mass vaccination “across all breeding herds — all sows and gilts – three times a year. Acknowledging that a classic influenza season no longer exists, the targets are fall, winter and spring.

“By vaccinating everything at the same time, we’re trying to raise the antibody levels and minimize the impact of any new influenza viruses that come into the herd,” Johnson said.

In between mass vaccination, any gilts entering the herd are vaccinated for influenza as part of the pre-breeding vaccination program.

The Carthage veterinarians are happy with the results so far. “We’re pretty comfortable that we aren’t seeing clinical disasters when new influenza viruses enter our herds,” he added.

Although the genetic diversity of the influenza virus continues to challenge and frustrate producers and veterinarians, “that doesn’t mean you stop trying,” Johnson said. “We have to keep driving toward better solutions.”