Iowa agriculture officials are working quickly to “stamp out” a confirmed case of pseudorabies (PRV) in a small commercial swine herd – the first detection of the virus in a U.S. commercial site since it was officially eradicated in 2004.
The detection, confirmed on April 30, involved five boars in a small commercial herd with less than 100 animals. While the virus has been absent from commercial herds for two decades, it remains endemic in feral swine populations, which is the suspected source of this “spillover” event.
Aggressive Containment Strategy
Following established USDA pseudorabies program standards, the affected site is being depopulated and all animals will be disposed of on-site to prevent any spread.
“The standards also require that we conduct surveillance around the site,” says Iowa Secretary of Agriculture Mike Naig. “A five-mile radius circle has been drawn around the positive site. Swine facilities within that radius will need to test for pseudorabies within the next 15 days.”
A secondary, two-mile radius circle has also been established. Farms within this inner circle must undergo a second round of testing 30 days after the original site is fully cleaned and disinfected. Naig confirmed that every producer within these zones was contacted by late Thursday.
Tracing the Source
The investigation points to a direct trace-back: the five positive boars were part of a shipment received several months ago from an outdoor “transitional” herd in Texas.
“We coordinated with the state of Texas, who began testing the herd of origin immediately on Monday,” Naig says.
The virus was caught during routine screening at the Iowa operation. While the five boars tested positive, the remaining pigs on the Iowa site tested negative. Naig notes that because there was no spread within the facility, it provides a “strong indication” that there was no spread outside the facility either.
The Science: Why PRV is a Challenge
Pseudorabies is a herpes virus, which presents unique challenges for eradication. Iowa State Veterinarian Dr. Jeff Kaisand explains that unlike many viruses that are cleared by the immune system, herpes viruses can remain dormant in the body.
“The virus can hang out and hide in the cranial nerves of the brain and the tonsil,” Kaisand says. “Pigs may recover and stop shedding, but the virus remains. Under stress, it can resurface.”
While the virus spreads primarily through nose-to-nose contact, it can also move via aerosols or contaminated equipment. Despite the risk, Kaisand emphasizes that vaccination is not currently an option for the industry.
“We are not expecting area spread, and vaccine raises trade issues,” Kaisand says. “We don’t want to vaccinate our populations and confuse natural infection with vaccine.”
Trade and Safety Outlook
Because pseudorabies is a reportable disease, the USDA has notified international trading partners, but the impact is expected to be minimal.
“There is always a potential for trade disruption, which is why we moved so swiftly,” Naig says. “We anticipate minimal, if any, short-term trade disruptions.”
Naig also stressed that the detection is not a food safety concern. Pseudorabies does not pose a risk to human health, and the U.S. pork supply remains safe.
Remain Vigilant
What producers can do is what they always should do – practice good biosecurity, Naig says.
“This is an isolated, specific incident here that has a direct trace back to this Texas farm,” Naig says. “Biosecurity is important every single day for animal health. It is important for livestock producers of all species.”
Kaisand adds that biosecurity is “protection from the unknowns, not the knowns.”
