Options
Article

Lessons Learned in Dealing With IAV-S in Sow Herds

Authors
  • Bob Thompson
  • Larry L Coleman

Abstract

The usual McRebel protocol was utilized, as had been the case in all the previous eliminations. In an effort to push the maternal antibodies higher we added in the Sequivity NA vaccine prefarrow. The NA was enough to make the elimination a success. Since the success with the NA vaccine, we have used two whole herd vaccinations for two outbreaks in negative herds with H1 human-like viruses. It has been successful in both those cases. I do realize that many times the H1 viruses aren’t very fit for the pig and the viruses may die out on their own. We just did not want to take the chance.

How to Cite:

Thompson, B. & Coleman, L. L., (2026) “Lessons Learned in Dealing With IAV-S in Sow Herds”, ISU McKean Swine Disease Conference 2026(1), 25-26. doi: https://doi.org/10.31274/swinedisease.25843

Downloads:
Download PDF
View PDF

10 Views

3 Downloads

Published on
2026-06-22

Peer Reviewed

License

All rights reserved

Thompson_Lessons Learned IAV-S_TP

Introduction/Background

Most of my experience in dealing with influenza has been in the breeding stock environment, eliminating the virus from sow herds to create flu negative weaned pigs and ultimately sow herds. My initial experience was in creating a negative genetic nucleus herd for PIC when the Apex GN was stocked in 2008 1. Following that, I started working on elimination projects within the PIC multiplication herds 2. In all these projects we used the Harris Biologics Replicon technology which subsequently became the Merck Sequivity HA vaccine of today. In one of the projects, when we were having trouble eliminating the virus with the HA vaccine, we added in Zoetis’s FluSure as a heterologous Prime Boost. It helped us increase the maternal antibodies enough to be able to wean PCR negative pigs. 3, 4 All of the herds I worked with had internal replacements, which makes it harder to maintain the negative status.

Within the past five years Dr. Coleman and I had a persistent H3N2 virus. We were unsuccessful in eliminating the virus with just the HA vaccine. The usual McRebel protocol was utilized, as had been the case in all the previous eliminations. In an effort to push the maternal antibodies higher we added in the Sequivity NA vaccine prefarrow. The NA was enough to make the elimination a success.

Since the success with the NA vaccine, we have used two whole herd vaccinations for two outbreaks in negative herds with H1 human-like viruses. It has been successful in both those cases. I do realize that many times the H1 viruses aren’t very fit for the pig and the viruses may die out on their own. We just did not want to take the chance.

The Pipestone veterinary group has presented several good elimination protocols that you can reference beyond the ones I presented in the early 2000’s 5, 6.

Lessons Learned

  1. Decide what your goal is with the herd, at the very least, in my opinion, you want to wean a flu negative pig.

  2. For the overall health of the sow herd, influenza vaccination of some sort is important. It can be a commercial or autogenous product.

  3. Dr. Coleman and I prefer to vaccinate gilt replacements with two doses of the HA autogenous vaccine prebreeding.

  4. Boostering the sow herd depends on the influenza status of the weaned pigs. If they are PCR negative in oral fluids, it is not necessary to vaccinate the whole herd.

  5. If weaned pigs are PCR positive then implement a prefarrow booster to improve the maternal antibodies.

  6. I recommend sequencing the IAV-S field virus for both the HA and NA portions to make a decision on which vaccine to use.

  7. Due to the ease of using a genetic sequence, we have chosen the Sequivity HA vaccine for the herd and gilt replacements.

  8. We keep dendograms of the viruses circulating in our herds and design the vaccine from the most current ones circulating.

  9. When the Sequivity NA vaccine became available as an off-the-shelf product, we started using it if the sequence similarity is close to what is in that vaccine.

  10. The data bank isn’t as detailed with the H1 viruses so we have used the NA vaccine when the similarities are not as close as we normally use.

  11. Research has shown influenza viruses circulate more frequently in the Fall and Spring. Many producers have gone to whole herd vaccinations twice a year to have the best immunity in the herd.

  12. Vaccinating gilts as mentioned above and boostering the sows prefarrow is another method of keeping maternal antibodies high.

When there is good herd location and high biosecurity protocols most new viruses enter via employees. I encourage all staff to get an annual influenza booster realizing the vaccine isn’t always closely matched to what may be circulating that year. We also have employees take temperatures daily for screening to reduce new introductions as much as possible. In addition to the references listed below, the Merck Flu Playbook is an excellent resource. The link is included below.

References

Culhane et al. (2019) Efficacy of Prime-boost Vaccination Protocols in Pigs Challenged with Influenza A Viruses. AASV, 164. doi: https://doi.org/10.3390/v12090968

E. Koep (2026) Practitioner Experiences with IAV Elimination: Success and failures AASV Preconference #5

E. McDowell (2024) Practitioner Perspective on Influenza Management AASV Preconference #3

Flu Playbook https://www.merck-animal-health-usa.com/downloads/swine-influenza-protocol-booklet/

Thompson et al. (2009) Creating an SIV Negative Sow Herd. Leman, 59.

Thompson et al. (2016) Elimination of Influenza A Virus in Multiple Breed-to-wean Herds. Leman Conference 2016.

Thompson et al. (2020) A Heterologous Prime Boost Mass Vaccination Protocol for IAV-S Control. AASV 2020, 93.