Time for a change? Farms achieve IAV-S-negative pigs after switching to whole-herd vaccination, By Micah Jansen, DVM – Managing, Technical Services Veterinarian, Zoetis

Influenza A virus in swine (IAV-S) continues to be costly for U.S. pork producers. A 2008 study estimated IAV-S losses to be $10.31 per market hog.¹ In 2012, the cost of IAV-S as a coinfection with other pathogens, such as porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae (Mhp), was reported to be $10.12 to $10.41 per head.⁴

What’s new with IAV-S?

What’s always new with flu is what’s circulating. Flu is very good at changing, and the swine industry continues to see it evolve.

“We must continue to improve the ways we control it or, in some scenarios, even eliminate it. And let’s not forget that influenza is a zoonotic disease, so we’re not only thinking about the health of our pigs, but we are also thinking about the health of our caregivers and the health of the public,” said Micah Jansen, DVM, managing U.S. Pork Technical Services Veterinarian at Zoetis.

An effective influenza strategy is key

An effective vaccination protocol is imperative to controlling influenza in swine, but when your usual practice isn’t yielding successful results, rethinking your influenza control strategy may help improve outcomes.

Jansen cites two examples of changing the approach to managing IAV-S.

Recalling the experiences of a southern Minnesota 1,200-sow farrow-to-wean herd and a 3,600-sow farrow-to-wean herd in Iowa, she noted, “In both cases, we shifted our objective to reducing the amount of virus moving around the sow farms. We wanted to build homogenized immunity across the entire herd, and whole-herd vaccination targets that.” As such, in both cases, influenza vaccine was administered to the breeding herd simultaneously.

Leveling the pigs’ playing field

Whole-herd vaccination leads to homogenized immunity for the entire herd. It equalizes the herd’s susceptibility to IAV-S because it establishes similar levels of antibodies in the adult animals, which they pass on to their piglets.² In these conditions, the virus tends to run its course quickly.

“If influenza comes in and the whole herd just got a booster, the animals will be protected,” Jansen explained. Whole-herd vaccination also reduces the likelihood of subpopulations developing within a herd, because the entire herd is vaccinated at the same time. In contrast, the prefarrow method staggers the timing of vaccinations to coincide with when sows are due to farrow. The prefarrow approach focuses on ramping up antibodies within the sows so they will pass them on to their piglets. However, because sows are at different stages of gestation and vaccination timing is dependent upon when they farrow, subgroups of sows with varying levels of antibodies can develop within the population.

Clinical piglets and PRRSV coinfection is what prompted different vaccination approachs. Jansen points out that both farms in the cases mentioned were using a prefarrow vaccination strategy and were still experiencing clinical signs in suckling piglets and the nurseries.³

The southern Minnesota facility was using a two-dose autogenous influenza vaccine in breeding females at five weeks and three weeks prefarrowing. The Iowa system, which was also struggling with PRRSV in addition to influenza, used FluSure XP® vaccine approximately three weeks prefarrowing in all sows and gilts.

After both approaches yielded less-than-optimal results, the farms’ veterinarians recommended, and management teams implemented, a two-dose breeding herd vaccination protocol using FluSure XP.

The vaccination timing for both farms occurred in late winter/early spring. Timing is vital because, as Jansen points out, “Whole-herd boosters should be given before peak influenza season hits, and spikes tend to happen in the fall and early spring.”

The southern Minnesota farm that had switched to FluSure XP achieved IAV-S-negative pigs five weeks after administering the second dose to the breeding herd. Similarly, the Iowa herd with the PRRSV coinfection had nearly eliminated clinical signs five weeks after the second vaccination. Caregivers reported that coughing piglets in the farrowing room were hard to find.

A whole-herd vaccination protocol with a broad, cross-protective vaccine, such as FluSure XP, combined with proper management of piglets and replacement gilts can help effectively control disease in herds. FluSure XP includes H1N1 Gamma, H1N2 Delta-1, H3N2 Cluster IV-A and H3N2 Cluster IV-B.

Producers and veterinarians should implement a vaccination approach that supports the growth and well-being of healthy pigs to avoid financial losses. Mortality costs from influenza coupled with decreased productivity and increased medication costs equate to money left on the table, so it pays to invest.

Tips to address IAV-S in your herd

Don’t assume your farm is infected with the same strain you had previously or one you’ve heard about on nearby farms. Jansen offers three tips for managing influenza on your operation:

1. Work with your veterinarian to conduct diagnostics to identify exactly which strains are circulating in your barns.
2. Look at information accessible from the U.S. Department of Agriculture surveillance programOpens in a new window. This will help you understand what’s circulating in your region and determine the risk of exposure to other strains circulating.
3. After uncovering current circulation patterns, formulate a plan of action. The plan should include the following:
   1. Vaccination — This is an excellent way to improve herd immunity. Work with your herd veterinarian to determine the best vaccination approach to meet your goals.
   2. Biosecurity — Focus on pig movement risks as well as fomites. Because influenza is zoonotic, it’s also important to ensure caregivers are consistently washing their hands, wearing gloves, using hand sanitizer and changing coveralls after working with high-risk populations.
   3. Ongoing surveillance — Many producers are moving towards ongoing surveillance, so even if they don’t see clinical signs, they are regularly monitoring. Depending on their goals, other producers may choose to test when clinical signs, including fever, clear nasal discharge, a barking cough, lethargy and/or going off feed, are present. Your herd veterinarian can help establish the right monitoring program.

“With influenza, it’s important to remain focused on interventions to reduce transmission and homogenize immunity,” she said. “If we focus on this, we can effectively reduce the costly burden of influenza.”