Cats in the United States died after being fed raw milk from cows infected with highly pathogenic avian influenza (HPAI) A, researchers reported on April 29.
The cats displayed symptoms just before death, including stiff movements and blindness.
Postmortem testing of two of the cats showed gross lesions or markers of severe virus infection. Researchers also discovered lesions in cows they examined.
Samples from the cats also tested positive for H5, a subtype of influenza A virus.
The evidence was consistent with previous reported infections in cats that were suspected to have been transmitted by wild birds, the original species with the bird flu, researchers said.
“Although exposure to and consumption of dead wild birds cannot be completely ruled out for the cats described in this report, the known consumption of unpasteurized milk and colostrum from infected cows and the high amount of virus nucleic acid within the milk make milk and colostrum consumption a likely route of exposure,” they wrote.
“Therefore, our findings suggest cross-species mammal-to-mammal transmission of HPAI H5N1 virus and raise new concerns regarding the potential for virus spread within mammal populations.”
They said that HPAI infection should be considered when cats display neurologic symptoms and blindness, and called for additional studies to confirm transmission from cows to cats.
The paper was published by the U.S. Centers for Disease Control and Prevention (CDC). The authors did not list conflicts of interest or funding sources.
Gail Hansen, the former state veterinarian for Kansas, said on the social media platform X, formerly Twitter, that the paper “raises concerns about spread to other animals.”
“Looks like ingestion of contaminated milk by cats may be another exposure route, so more chances for the virus to further adapt,” she wrote.
“This report implicates raw milk ingestion by cats on dairy farms as a likely route of exposure and shows just how ‘highly pathogenic’ this virus is for domestic cats,” Meghan Davis, an associate professor at the Johns Hopkins Bloomberg School of Public Health, added.
HPAI cases among cattle first began being reported earlier this year, although there are indications cattle began becoming infected in late 2023. Researchers are still working to pin down the exact dates the virus started spreading in cows.
CDC officials had said on April 25 that six confirmed cases of HPAI were confirmed in cats across multiple dairy farms. New Mexico officials said earlier in April that one cat in Curry County tested positive.
A spokesperson for the Texas Animal Health Commission told The Epoch Times in an email on April 30 that there were six confirmed cases in cats.
“While we can confirm these cats were on affected premises, we do not have information related to the number of these cats that drank milk from affected cows,” the spokesperson stated.
As of April 29, federal officials have confirmed HPAI cases among 34 cattle herds in nine states, including Colorado, Idaho, and Michigan.
A single human case in Texas has been confirmed this year. One earlier case was confirmed in Colorado in 2022.
U.S. Department of Agriculture officials advise people with animals to avoid housing multiple species together, especially on farms. Animals suspected of having or testing positive for the flu should be isolated.
Authorities also advise people to keep cats indoors when possible. They say raw milk or raw milk products from cattle with the flu should be heat-treated or pasteurized before being fed to cats or other animals.
Wastewater Detection
Another new paper, published ahead of peer review, detailed how samples from wastewater in 18 states showed spikes in influenza A viruses.Emery University environmental health professor Marlene Wolfe and her co-authors said that samples from 59 of 190 wastewater treatment plants included in the testing showed increases in the viruses, including plants in Kansas, Michigan, and Texas.
The researchers suggested that the spikes came from the dumping of milk into the sewage system. Officials have been advising farmers to dump milk from affected cattle or feed it to other animals after HPAI is detected on their farms.
“If dairy industry activities in these sewersheds are a primary source of H5 in wastewater, this suggests that there are may be additional, unidentified outbreaks among cattle with milk sent to these facilities since milk from infected animals is required to be diverted from food supply,” the researchers said.
Limitations of the research included testing for H5, not HPAI, meaning the measurements could capture other H5 viruses.
Some authors listed employment at Verily Life Sciences as a competing interest. The study was funded by the Sergey Brin Family Foundation.
