U.S. Scrapie-Free Status Delayed After New Oregon Case Confirmed

Just when the United States was within reach of a major animal health milestone, a single sheep has reset the clock.

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has confirmed a case of classical scrapie in a sheep slaughtered at an Oregon processing facility. The diagnosis, confirmed by the National Veterinary Services Laboratories following genotype analysis and additional testing, is the first U.S. case identified since January 2021 and could delay the nation's long-awaited scrapie-free designation by several years.

The discovery is a significant setback for a disease eradication effort that has spanned nearly eight decades. The United States was in the sixth year of the required seven-year waiting period needed to earn official scrapie-free status from the World Organisation for Animal Health (WOAH). With this newly confirmed case, the earliest the country could now receive that designation is approximately 2033.

For veterinarians working with sheep and goats, the case is a reminder that even diseases considered nearly eliminated still require constant vigilance.

Scrapie is a fatal neurodegenerative disease caused by abnormal prion proteins that affect the central nervous system of sheep and goats. Similar to bovine spongiform encephalopathy in cattle and chronic wasting disease in deer and elk, scrapie slowly destroys nervous tissue over several years before clinical signs become apparent. Infected animals may develop behavioral changes, intense itching, tremors, incoordination, weight loss, and eventually die. There is no treatment and no cure.

The affected sheep was identified through USDA's routine slaughter surveillance program, one of the cornerstones of the National Scrapie Eradication Program. Unfortunately, investigators face an immediate challenge because the animal was not carrying an official ear tag, making it much more difficult to determine where it originated.

APHIS and the Oregon Department of Agriculture are now conducting an epidemiologic investigation to trace the infected animal back to its flock. Tissue matching and parentage testing are also being performed on additional sheep processed alongside the infected animal in an effort to identify its source.

The missing identification has become one of the biggest take-home messages from the case. Federal officials noted that the inability to immediately trace the animal highlights why official identification requirements remain essential, even as disease prevalence reaches historic lows.

The progress made over the past two decades has been remarkable. In 2004, approximately one out of every 359 sheep tested positive for scrapie. Since the launch of the National Scrapie Eradication Program in 2002, surveillance, improved flock management, genetic selection for resistant animals, and mandatory animal identification have reduced disease prevalence in targeted sheep by more than 99 percent.

Many veterinarians entering practice today have never encountered a case of scrapie, which makes this diagnosis especially noteworthy. While uncommon, the disease continues to carry substantial economic consequences. APHIS estimates scrapie costs the U.S. sheep and goat industries between $10 million and $20 million each year through production losses, carcass disposal, trade restrictions, and disease control efforts.

The Oregon case serves as a reminder that eradication programs are marathons, not sprints. Diseases with incubation periods measured in years require equally long periods of surveillance before regulators can confidently declare a country disease-free. Because scrapie can incubate for roughly five years before clinical signs appear, international standards require seven consecutive years without a confirmed case before disease-free status can be granted.

For veterinarians, producers, and regulatory officials, this latest case reinforces the importance of surveillance, traceability, and maintaining strict identification practices, even when success appears to be within reach. After nearly 80 years of work, one unidentified sheep has postponed a milestone that the U.S. sheep industry had been waiting decades to achieve.