Dealing with today’s PRRS

Jeff Okones, DVM, Pharmgate Animal Health

First described in the late 1980’s as Blue Ear or Mystery Pig Disease, Porcine Reproductive and Respiratory Syndrome (PRRS) has become a perennial and expensive challenge for U.S. pork producers, costing the industry an estimated $664[1] million annually. PRRS continues to lurk in epidemic and endemic forms and has been described as the most economically significant disease to affect U.S. pork production since the eradication of classical swine fever.

“Over the 25 years we’ve fought PRRS, there has always been an evolution of increasing virulence in isolates of significance,” says Michael Roof, Chief Technology Officer Vaccines and Immunotherapeutics research and innovation platform at Iowa State University.

The Swine Health Information Center in Ames, Iowa, has been tracking a new, highly pathogenic variant, PRRSv 1-4-4. It became a predominant strain in 2021 and is expected to remain important heading into the prime season for the virus in the coming months. This Lineage 1C virus is especially virulent and has caused a lot of problems in the Midwest and upper Midwest.[2]

“The current 1-4-4 situation isn’t a debate about whether it is or isn’t more virulent than others,” says Roof. “The fact of the matter is, it’s the predominant isolate in the field, it’s significant and it seems to cause problems even in highly vaccinated or stabilized herds.”

Meanwhile, PRRSv isolates 1-7-4 and 1-8-4 also remain on the radar and cannot be overlooked.

While PRRS is complex, difficult to control, and has no single or universal control strategy, three tools remain available to help mitigate its impact:

  1. Biosecurity: Ensure biosecurity protocols are up to par. As the virus evolves, evaluate procedures and update as needed, ensuring all members of your team are aware of any changes.
  2. Diagnostics: Use diagnostic tools to determine the source of health challenges. Many facilities routinely monitor oral or tissue fluids. Add PRRSv monitoring, if possible, to see whether herd prevalence trends up or down. Also keep an eye on animal performance, weight gain, feed consumption and treatment cost – all of which are direct and indirect indicators of overall health. PRRS has a major influence on these performance factors, which means they can be additional indicators of this health challenge.
  3. Vaccine options. A robust vaccine and pig health protocol can reduce the incidence and severity of clinical PRRS.

Each farm is different. To optimize your vaccine protocol, consider the following factors:

  • Vaccine selection: Optimal selection depends on your herd’s status and challenge levels, and vaccines from contemporary strains are a strong foundation. Today’s PRRS vaccines fall into two general categories that stimulate different immune responses:
    • Commercial modified live vaccines (MLV), in which a virus is attenuated to a form that can be recognized by the immune system to mount an effective response but is unable to cause the disease or revert to the more virulent form.
    • Autogenous vaccines that are inactivated or killed.

“Modified live vaccines (MLV) provide a statistically significant reduction of clinical signs,” explains Roof. “They don’t eliminate disease, and they don’t provide sterilizing immunity. Vaccinations, in combination with biosecurity and other tools, are designed to allow producers the ability to maximize commercial success and minimize disease and treatment costs.”

Be consistent with the vaccine you choose.

“Pick a vaccine and give it time to work so you can evaluate its effectiveness,” suggests Roof. “Use it consistently to get the best results and don’t allow gaps in your protection program. You need to achieve broad and consistent immunity.”

  • Optimize timing: Determine when PRRS generally occurs within your herd and location, then implement vaccine protocols three to four weeks ahead of that time to elevate herd immunity. While it may be convenient to vaccinate piglets at three weeks of age, that may not fit in exposure windows. Adjust plans accordingly. Also note the PRRS status of the pig at vaccination plays a significant role in vaccine success.
  • Follow label directions: Use the full vaccine dose because attenuation matters. You reduce the effectiveness of any product if you don’t use it in the manner it was intended. Protection from the full dose gives pigs the best chance to keep performing if exposed to PRRSv.

Ultimately, “The way to knock PRRS down is through consistent vaccination with careful timing, full-herd coverage and strong pig health management,” concludes Roof.

PRRS is multifactorial in nature, and there is no silver bullet for control. The PRRS virus supresses the immune system, increasing the pig’s susceptibility to secondary bacterial infections. A holistic health protocol, including careful vaccine selection and timing, as well as judicious antibiotic use, will optimize health and profitability.

Pharmgate Animal Health can provide you multiple tools to mitigate the impact of PRRS. PRRSGard is a modified-live PRRS vaccine designed with a unique chimeric construction. It uses two contemporary lineage strains and is research-proven to be efficacious against PRRSv, reducing viremia and lung lesions from PRRS-associated pneumonia in growing pigs. Additionally, Pharmgate has a broad portfolio of therapeutics in multiple administration forms to meet your health protocols.

Talk to your veterinarian about PRRS control with PRRSGard. Visit or for more information regarding your pig health needs.

[2] Swineweb. June 8, 2021. Farmscape. Available at: