H5N1 cases in a Washington cat and Dutch cows sharpen vigilance

A suspected fatal H5N1 infection in an outdoor cat in Washington state and follow-up testing on a Dutch dairy farm are the latest reminders that avian influenza is still finding new ways into companion animals and livestock. Scott Weese highlighted the Washington cat case as another likely bird-to-cat spillover, while Dutch authorities’ investigation of a Friesland dairy farm, triggered by an H5N1-positive cat, first found antibodies in one cow and then, according to a later local update cited by Weese, in five cows on the farm. Dutch officials said no active virus was detected in the cattle sampled, and Wageningen University & Research said the initial cow had signs in mid-December 2025 consistent with infection, including mastitis and reduced milk yield. (wormsandgermsblog.com)

Why it matters: For veterinary professionals, the signal is less about surprise than surveillance. Cats continue to act as highly susceptible spillover hosts, often with severe or fatal disease, and may serve as sentinels for undetected farm exposure. A recent systematic review identified 607 reported avian influenza infections in felines across 18 countries from 2004 to 2024, with a sharp rise tied to H5N1 clade 2.3.4.4b in domestic cats. On the cattle side, the Dutch case matters because it suggests European dairy cattle can be infected, even if infection is mild or clinically missed, echoing concerns raised after the U.S. dairy outbreak. (academic.oup.com)

What to watch: Watch for final serology and any epidemiologic findings from the Dutch farm, plus whether veterinary and public health agencies broaden testing guidance for cats with neurologic or respiratory disease and for dairy herds linked to unexplained feline illness. (wur.nl)