The Importance of Vaccination in Controlling Transmission of Influenza A Virus in Swine (IAV-S)

Understanding transmission for better control of IAV-S
To properly control IAV-S, we must understand the way in which it is transmitted—both directly and indirectly—and the risks it poses to all swine herds.

Pigs are born free of IAV-S.1 But on farms where IAV-S is endemic, pigs are exposed to disease early on. As we know, maternal antibodies begin to wane as early as 8 weeks, and often pigs become infected prior to weaning. 2,3 Here, transmission of IAV-S is direct, via pig-to-pig or droplet transmission route: Pigs infected with IAV-S begin to shed infectious viral particles through nasal secretions as early as 1 day after infection and can continue to shed for 7 days. 4,5

IAV-S can spread by direct transmission through all production phases

Infection Chain Graphic Infection Chain Graphic

It is important to remember that transmission of IAV-S is not limited to direct nose-to-nose contact. IAV-S may also be spread via airborne viral particles emitted by infected pigs.6 A recent study showed that it is possible for these viral particles to travel up to 1 mile downwind of the infected barn, extending the risk of infection beyond a single system.7

Reducing transmission within and between systems
The issue of transmission is compounded by the constant movement of pigs. In 2015, it was estimated that approximately 1 million pigs are transported every day, including weaned pigs moving to distant locations and replacement gilts traveling to new gilt development units.8,9 If any of these pigs are infected with IAV-S, they may transmit disease to other pigs, directly or indirectly-even in the absence of clinical signs.10

In his presentation at World Pork Expo 2018, Clayton Johnson, DVM, emphasized the ever-present risk of IAV-S: Regardless of origin, the virus pushes its way through the supply chain as pigs are moved, transmitting to and infecting groups downstream.11

So, what can be done to decrease the risk? Implementing healthy habits, such as limiting the movement of young pigs, can reduce the transmission of IAV-S within the herd.7 But, as we know, IAV-S is frequently transmitted in other indirect ways:

  • Transmission via fomites can be reduced by practicing good group-to-group hygiene12-14
  • Regional transmission can be limited by appropriately managing new arrivals15
  • Aerosol transmission has been shown to be mitigated using air filtration systems16

Practicing biosecurity measures like these as part of a whole-herd approach (WHA) can help reduce direct and indirect transmission and minimize overall exposure to IAV-S.

Ingelvac Provenza® is proven to reduce shedding and transmission16
In addition to minimizing exposure, the objective of a WHA is to maximize immunity through vaccination. In fact, studies have shown that transmission of IAV-S can be significantly reduced by vaccination.11 INGELVAC PROVENZA is not only proven to protect pigs against IAV-S infection, but it is also proven to decrease shedding, which reduces transmission in a population.17 In fact, in a recent study in 3- to 5-day-old pigs vaccinated with INGELVAC PROVENZA and later challenged with a heterologous H1N1, pigs vaccinated with INGELVAC PROVENZA (n=36) had a median of 2 shedding days versus 4 for controls (n=48).17 Additional heterologous challenge studies of H3N2 AND H1N2 demonstrated similar findings.17

Learn more about reducing transmission of IAV-S using a WHA that includes vaccination with INGELVAC PROVENZA. Talk to your Boehringer Ingelheim representative or visit



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