While foot-and-mouth disease (FMD) makes its way through regions of Europe and Asia, a “lookalike” virus – Senecavirus A (SVA) – is gaining momentum in the U.S. swine industry.
Experts warn that SVA is clinically indistinguishable from FMD. Both viruses cause vesicular lesions on the snout, mouth, and coronary bands, often resulting in sudden lameness. With new FMD serotypes emerging globally that current vaccines cannot stop, the stakes for U.S. biosecurity have never been higher.
“Vigilance for detection and diagnostic confirmation of vesicular lesions of swine continues to be critical to prevent FMD entry into the U.S. especially with increasing global disease activity,” says Dr. Ann Carpenter, a veterinary medical officer with USDA APHIS Veterinary Services.
Understanding the virus, its pathogenesis, routes of transmission, disease trends, as well as control and mitigation steps, can help producers protect their herd from this emerging disease and enhance prevention for other vesicular diseases such as FMD.
SVA Seasonality: Why Summer and Fall Pose the Highest Risk
Data from the Morrison Swine Health Monitoring Project (MSHMP), funded by the Swine Health Information Center (SHIC), reveals a distinct seasonal pattern for SVA in breeding herds.
- Cases spike in the third quarter (July–September) and remain elevated through the fourth quarter (October–December).
- Surveillance shows a concentration of cases in the Midwest during the latter half of the year.
- While cumulative incidence remains below 2.5% annually, the virus continues to circulate, particularly in areas with high pig density.
Dr. Mariana Kikuti, assistant professor at the University of Minnesota, notes that for sites with repeat outbreaks, the median interval is approximately 402 days.
“This highlights the potential for re-introductions or persistent circulation within herds,” she explains. “The observed seasonality and regional concentration suggest opportunities for more targeted biosecurity enhancements and surveillance efforts, particularly in the Midwest during the latter half of the year.”
Viral Persistence: The Role of Boars and Carrier Pigs
One of the most challenging aspects of SVA is its ability to hide within a herd. Dr. Diego Diehl, a professor at Cornell University, explains that SVA is not just an acute infection, it can persist for a long time in the herd.
- The virus can persist in a pig’s tonsils for 60 days or more, long after clinical signs vanish.
- Recent studies indicate viral RNA can be detected in boar semen for up to 90 days.
- Environmental stressors, transport, or farrowing can cause “recrudescence,” where the virus begins shedding again in seemingly healthy animals.
Feed as a Transmission Route
Research also confirms that SVA is highly stable in common feed ingredients, particularly under cooler conditions. The virus can survive in soybean meal and dried distiller’s grains with solubles (DDGS) for up to 90 days at 39° Fahrenheit.
Controlled studies demonstrated that pigs can become infected simply by consuming SVA-contaminated feed, suggesting that biosecurity protocols must extend to the feed supply chain.
The Danger of Complacency
While the U.S. remains FMD-free, the global landscape is shifting. Kikuti says there is a need for more standardized surveillance of SVA and improved serological tests to accurately identify previously exposed or carrier animals in a population where the virus is now endemic.
“One of the unique and also most problematic characteristics of this virus is the ability to establish persistent infection in carrier animals, just like FMD,” Diehl says. “It definitely contributes to transmission in the field, and it’s probably one of the ways that the virus circulates and is transmitted through live animals.”
Through funding from USDA, researchers recently identified amino acids in the virus genome that contribute to persistence, Diehl adds. They are now working to develop a live attenuated vaccine as a potential tool to help in the control of virus.
“SVA causes a pretty remarkable problem,” Diehl says. “The fact that we have a vesicular disease agent endemic in our swine population is concerning to me because it is clinically indistinguishable from FMD. People may think that it’s SVA, but it may not be SVA – it could be one of the other FADs that have higher consequences. That could lead to delayed detection of those more significant foreign animal diseases that cause vesicular disease, which would be a big problem.”
Learn More Here:
The Swine Health Information Center, in collaboration with the American Association of Swine Veterinarians, hosted a webinar entitled “Senecavirus A as an emerging disease risk for FMDV” and is now available for on-demand viewing here.
