Federal officials today announced the first H5N1 avian flu detection in pigs, which was on a backyard farm in Oregon where an outbreak was recently reported in poultry.
In a statement from the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS), officials said the farm is located in Crook County in Oregon, which has a mix of poultry and livestock, including five pigs. The quarantined location also has sheep and goats.
When H5N1 emerged in dairy cattle earlier this year, officials worried about potential spread to pigs, due to the impact on farming and food supply, but also because pigs are known to be a mixing vessel for zoonotic and human influenza viruses. However, it’s not yet clear if the pigs had systemic infection or if contamination on the farm led to positive nasal swab results.
Pigs shared environment with sick poultry
The pigs and poultry shared water sources, housing, and equipment, factors known to enable transmission between the species, APHIS aid.
Though the pigs showed no illness signs, the Oregon Department of Health and the USDA tested the five pigs out of an abundance of caution. The pigs were euthanized for additional diagnostic analysis. Test results were negative for two pigs and are pending for two others.
“This farm is a non-commercial operation, and the animals were not intended for the commercial food supply. There is no concern about the safety of the nation’s pork supply as a result of this finding,” APHIS said.
The group had confirmed the virus in the backyard flock on October 25. The Oregon Department of Agriculture said today that 70 birds were humanly euthanized last week and that the location is under quarantine.
Initial genetic sequencing has been done at the USDA’s National Veterinary Services Laboratories, and though the genotype wasn’t noted, officials said there are no H5N1 changes to suggest the virus is more transmissible to humans.
The H5N1 detection in pigs comes amid a recent rise in poultry outbreaks in some western states, which has occurred alongside wild bird migration along the Pacific Flyway.
Jury still out on whether pigs were infected
Michael Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), which publishes CIDRAP News, said it’s not yet known if the pig was truly infected or if the nasal passages had been contaminated by environmental exposure, a situation strongly suspected when a Colorado poultry culler tested positive in 2022 during nasal swabbing that was done as part of illness monitoring.
He said the necropsy examination will reveal if the pig was truly infected and if the virus was found deep in the pig’s lungs. “We’ll have to wait and see,” Osterholm said, urging caution in interpreting the new development.
He noted that earlier scientific work suggested that the virus doesn’t easily infect pigs.
