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Avian flu is no longer just a threat to birds. The latest data from the US Department of Agriculture (USDA)’s Animal and Plant Health Inspection Service (APHIS) reveals that the highly pathogenic avian influenza (HPAI) virus has been detected in a range of mammal species, including dairy cows, various types of cats, a fox, a seal, and most recently, rats and domestic indoor cats.
According to APHIS, over 500 cases of H1N1 in mammals have been identified in the United States since 2022. The latest detections include black rats sampled in January in Riverside County, California, an area recently affected by poultry outbreaks. Other reported mammalian infections include a fox in North Dakota, a bobcat in Washington state, a mountain lion in Wisconsin, and a harbor seal in Massachusetts.
Avian Flu in Domestic Cats
A report from the Centers for Disease Control and Prevention (CDC) documented cases of H5N1 in two indoor domestic cats in Michigan. While previous cases have been reported in outdoor cats on dairy farms, these were the first identified in strictly indoor cats. The cats exhibited severe respiratory and neurological symptoms, and both died. Their human owners, who worked on dairy farms, declined H5 testing, but other household members tested negative.
The CDC report suggested that farmworkers should take precautions such as removing clothing and footwear and washing off any animal byproducts before entering their homes.
Cross-Species Transmission No Surprise
Marie Culhane, DVM, PhD, a professor at the University of Minnesota’s College of Veterinary Medicine, noted that interspecies transmission of influenza A viruses has always been a concern.
“The more virus there is in our shared ecosystem, the more opportunities exist for other mammals and birds to get infected,” Culhane explained.
She advised clinicians to remain vigilant and continue testing for flu symptoms in both humans and animals. Diagnosis typically involves swabbing nasal, oral, or pharyngeal mucosa and using a polymerase chain reaction (PCR) test for influenza A subtyping. If symptoms have cleared, a serum antibody test can be used to detect prior exposure.
Preventing Transmission
The USDA emphasizes avoiding contact with sick or dead animals as the primary preventive measure. While most mammals do not appear to spread HPAI effectively, APHIS advises against handling infected wildlife and recommends washing hands with soap and water for at least 20 seconds after any potential exposure.
The agency also warns against feeding pets raw food or unpasteurized milk, as these can serve as transmission routes for avian flu and other pathogens.
Meanwhile, concerns over the virus’s evolution persist. A recent report from Canada identified an oseltamivir-resistant strain of H5N1 in poultry, though the implications for cross-species transmission remain unclear.
As the situation continues to evolve, APHIS maintains an updated list of mammalian infections on its website, providing crucial information for researchers, clinicians, and the public.
Disclaimer: This article is for informational purposes only and does not constitute medical or veterinary advice. Readers should consult relevant health authorities and professionals for guidance regarding avian flu and its impact on humans and animals.
