If we want to understand influenza A virus in swine, the industry really needs to get back to the simple side of complex, says Christa Goodell, technical manager for Boehringer Ingelheim Animal Health USA Inc.
“We actually have a much better appreciation for what it takes to report and to measure IAV-S. It’s been very hard to assess and say, ‘IAV-S causes this, it has this impact in my production system,’” Goodell says. “But we really need to do a better job helping producers, as well as ourselves as veterinarians, better understand the true cost of IAV-S, not only on its own but in the context of co-infections and the overall health of a herd.”
While better methods to measure IAV-S’s impact are needed, not just at closeouts but also in real time, one technique that has been successful in controlling IAV-S is the Whole Herd Approach. During Boehringer Ingelheim’s Pre-AASV Symposium, Goodell shared why WHA has worked so well during her presentation “IAV-S Control: Reminders of What Made Whole-Herd Approach a Success.”
Goodell says with high flu numbers and many different strains present, even on the same farm, IAV-S can be difficult to manage.
“Many pigs are exposed younger than 10 days of age,” Goodell says. “Trying to get pigs to have a great immune response when they are getting vaccinated at three days and then getting exposed at 10 days is really hard.”
The transmission rate for IAS-V is high and even low prevalence can still lead to flu in the nursery. Aerosols can carry IAV-S, particularly large droplets and aerosol transmission risk increases with an increasing number of shedding pigs. IAV-S is ever changing and multiple strains and co-circulating IAV-S is common in a herd.
Transmission rate can be reduced by maternal antibodies, but it still occurs. Maternal antibodies and killed vaccines protect against clinical signs/disease but they don’t prevent infection, antigenic drift or resident IAV-S diversity. Transmissions are also prolonged in maternal antibody pig populations.
“We also know pigs are born free of flu. This is not PRRS, this not something that comes in utero, this is not something the pigs pick up from colostrum, so our chance of success is quite high,” Goodell says. “We just need to address the transmission and we have to address the immunity.”
The goal is to reduce exposure in gilts and piglets and immunize so that circulation of the flu is prevented. It really comes down to “minimizing transmission, maximizing immunity,” Goodell says.
A control plan to reduce the influenza endemicity and its impact from farrow to finish, WHA takes a two-prong approach, which involves a strategy to push that resident flu out of the farrowing house to ensure the vaccine has a chance to immunize the pigs and then a strategy to eliminate that strain of flu from the gilt development unit.
The cornerstone of WHA is addressing subpopulations, such as new gilts and piglets and the older piglets in the farrowing house. Another risk factor to consider is human behavior.
Goodell says there are three key steps to implementing the WHA for Site 1 Endemicity:
- Characterize current status. Implement whole-herd vaccination in sow farms with actively circulating IAV-S. Include on-site growing pigs and gilts. Execute immunization plans to all subsequent replacement animals.
- Focus on high-risk farrowing house management activities. Assess movement of people, tools and animals. Implement best practices for biosecurity of neonatal pigs.
- Immunize all commercial pigs and replacement animals as early as day one.
The same procedure can be used during a herd closure event and should be included in all PRRS closure practices along with mass vaccination. A batch farrowing system is another opportunity to implement the WHA.
“If we batch farrow, we are all in and all out, as long as we do a good job of cleaning and disinfecting, and if our gilts aren’t bringing new flu in, we are actually ahead of the game in these systems,” Goodell says. “If we use vaccine to homogenize the populations, we are already there. Again, these are just opportunities where the Whole Herd Approach works.”