Senecavirus A (SVA) continues to be a concern for the U.S. swine industry. This endemic disease, characterized by vesicular lesions on the snout and feet, is clinically indistinguishable to foot-and-mouth disease. This makes investigations necessary for every suspected case to rule out this foreign animal disease and places a burden on state and federal animal health agencies.
In a study led by Cesar Corzo of the University of Minnesota, researchers examined just how often new SVA outbreaks occur in breeding herds. Since a major SVA outbreak in 2015, there has been a gap in comprehensive research on how often SVA occurs across U.S. pig farms, reports the Swine Health Information Center (SHIC).
This study, published in Animals, provides epidemiologic insights into SVA across U.S. breeding herds from January 2015 to December 2024 through analysis of data gathered from the SHIC-funded Morrison Swine Health Monitoring Project.
“Data included in this study is comprised of SVA PCR results originating from production systems participating in MSHMP as well as the type of specimen submitted and the official Premises Identification Number,” SHIC reports.
The sow population participating in MSHMP currently represents 60% of the total U.S. breeding herd. A total of 36,400 SVA PCR submissions were provided by the University of Minnesota and Iowa State University veterinary diagnostic labs (VDLs) from January 2015 to December 2024. SHIC says this robust dataset allowed for the assessment of SVA incidence, identification of temporal fluctuations, and characterization of regional patterns.
Notable findings include:
>Despite its clinical significance, the cumulative incidence of SVA in U.S. breeding herds remained low, generally less than 2.5% per year across the 10-year study period. Researchers say this suggests that while SVA continues to circulate, it affects a relatively small proportion of breeding herds annually. For sites experiencing more than one SVA outbreak, the median time interval between outbreaks was approximately 402 days, highlighting the potential for re-introductions and/or persistent circulation within herds.
>A notable temporal pattern was observed, with peak SVA incidence occurring during the third and fourth quarters of the calendar year (July to December). This suggests seasonality influences disease transmission dynamics, the researchers say. VDL reports further support this observation.
>SVA outbreaks were more frequently reported in the Midwest region. Though this finding is confounded with the high density of swine production in the Midwest, researchers say efforts to better assess disease distribution are still needed. The temporal and regional patterns suggest seasonal fluctuations and a regional disease burden, emphasizing the need for continued surveillance to better understand SVA dynamics.
>Factors like personnel and animal movement, dead animal management, and even vectors such as flies were noted in SVA transmission, reinforcing the importance of stringent biosecurity protocols.
“Overall, this study provides valuable, data-driven insights into the current epidemiology of SVA, enabling veterinarians and producers to enhance prevention and control strategies,” SHIC writes. “It underscores the ongoing need for robust and collaborative surveillance systems that integrate on-farm observations with laboratory diagnostics to provide a comprehensive picture of SVA dynamics. Specifically, 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.”
