Pseudorabies Is Back in Commercial Swine. For the First Time Since 2004

This was not a sick herd that triggered an alarm. Nobody called a hotline. A routine test came back positive, and the result stopped people in their tracks.

The USDA's Animal and Plant Health Inspection Service confirmed a detection of antibodies to pseudorabies virus in a small commercial swine facility in Iowa. The confirmation came via ELISA and latex agglutination testing through the National Veterinary Services Laboratories. It marks the first known case of pseudorabies in commercial swine since the disease was eradicated from the commercial herd in 2004. That is twenty-one years. And it came back quietly, through routine surveillance, which is exactly why routine surveillance exists.

WHERE IT CAME FROM

Traceback points to Texas. The five affected boars at the Iowa facility came from an outdoor production operation in Texas, and animals from that same Texas herd have also tested positive. APHIS is now working with officials in both Iowa and Texas to expand traceback, map the full scope of potential exposure, and identify any additional facilities that may have had contact with affected animals.

The likely source is not mysterious. Pseudorabies virus, also called Aujeszky's disease, was eradicated from U.S. commercial swine in 2004 but has never been eliminated from feral swine populations. It does not have to be. Feral swine carry PRV at high prevalence across much of the southern and central United States, and when outdoor commercial operations share fence lines or territory with feral pigs, spillover is a real and documented risk. An outdoor facility in Texas is exactly the kind of setting where that contact happens.

Eradicated from commercial swine in 2004. Back in 2025. The feral swine reservoir never went away.

WHAT PSEUDORABIES ACTUALLY IS

Pseudorabies is a herpesvirus, Suid herpesvirus 1, and pigs are its only natural host. In commercial swine it causes reproductive failure, respiratory disease, and neurological signs, with significant mortality in young piglets. Once a herd is infected, the virus establishes latency, meaning animals become lifelong carriers even after clinical recovery.

Despite the name, pseudorabies has nothing to do with rabies virus. The name comes from the clinical signs it produces in non-porcine species, which can mimic rabies. Most mammals are susceptible: cattle, sheep, dogs, cats, and wildlife can all be infected, typically through contact with infected pigs or contaminated environments. In non-porcine species the disease is almost always fatal, presenting as intense pruritus, self-mutilation, and rapid neurological decline. There is no treatment and no recovery.

The exceptions worth noting: humans, horses, and birds are considered resistant to PRV infection. This detection does not pose a risk to consumer health or affect the safety of the commercial pork supply.

WHY THE EXPORT PICTURE GETS COMPLICATED

APHIS has been direct about one consequence: there may be limited, short-term impacts on exports of U.S. swine and swine genetics. That is the diplomatic version of a real concern. Many of the United States' trading partners have strict pseudorabies-free requirements for imported swine and porcine genetic material. A confirmed case in commercial swine, even a geographically contained one, triggers scrutiny. The 2004 eradication was an enormous economic and regulatory achievement. The speed and transparency of the current response will matter for how trading partners interpret this detection.

WHAT HAPPENS NOW

APHIS is coordinating with the Iowa Department of Agriculture and Land Stewardship and the Texas Animal Health Commission on active traceback. The affected facilities are under investigation and exposed animals are being identified. The goal is to understand the full chain of transmission, contain any further spread, and build a complete picture of how these animals moved and who else they may have contacted.

For veterinary practitioners working with swine, particularly in outdoor or range production systems in states with significant feral swine populations, this is a reminder that the surveillance infrastructure exists for a reason. Routine testing found this. Routine testing is what makes early containment possible. The 2004 eradication was built on exactly that kind of systematic, unglamorous surveillance work, and so is the response to this detection.

Routine testing found this. Routine testing is what makes early containment possible.

THE BIGGER PICTURE

The feral swine population in the United States has been a reservoir and a risk for decades. Estimates put the feral pig population somewhere between six and nine million animals across at least thirty-five states, with the highest concentrations in Texas, Florida, and the Southeast. PRV prevalence in feral swine varies by region but is well established across the population. The interface between feral swine and outdoor commercial production is not going away, and this detection is a direct consequence of that interface.

Eradication from commercial swine was a landmark achievement. Maintaining that status requires ongoing vigilance, strong biosecurity at operations where feral swine contact is possible, and the kind of routine surveillance that catches a single positive before it becomes a cluster. This case is contained to a traceable source. Whether it stays that way depends on how fast and how thoroughly the response moves.

Vet Candy will continue to follow this story as traceback expands and APHIS releases additional findings. For the most current information, follow USDA APHIS at aphis.usda.gov.

Source: USDA APHIS National Veterinary Services Laboratories | Confirmation via ELISA and latex agglutination testing | Reporting by Vet Candy | myvetcandy.com