A Canada goose crosses the Denver Trolley tracks near Speer Boulevard during a snowstorm on February 16, 2022.
The highly pathogenic bird flu – or bird flu – sweeping the world has killed more than 12,000 wild birds in Colorado and the virus is also spreading through mammal populations, according to state wildlife officials.
And it’s unclear when the spread might slow.
“This is unprecedented,” said Kristy Pabilonia, director of clinical diagnostics for the College of Veterinary Medicine and Biological Sciences at Colorado State University. “The fact that it’s now so distributed with our wild bird populations, there are a lot of questions about the best next steps.”
That death toll is likely a “significant underestimate” of the true number of Colorado wild birds killed by the virus, said Colorado Parks and Wildlife spokesman Travis Duncan.
The number of birds in commercial flocks – mostly chickens and turkeys – being killed by the virus is much higher, leading, in part, to egg shortages and higher prices across the country.
State officials have twice tracked large-scale “mortality” of more than a thousand geese in northeastern Colorado, Duncan said. Once at Jumbo Reservoir, then Prewitt Reservoir. Additional and smaller fatalities have been tracked at most reservoirs near Lamar, he added.
Data collected by the US Department of Agriculture shows cases of bird flu in at least 30 of Colorado’s 64 counties. Among the birds killed are Canada and snow geese, horned owls, red-tailed hawks and five bald eagles.
In Denver, the virus claimed two Chilean flamingos (classified as captive wild birds), a swan goose and a scale-sided merganser, among a list of geese, ducks and owls, according to the data.
Domestic flocks have been hit hard (with nearly 6.3 million birds affected in commercial operations, according to USDA data), but at least humans have the ability to quarantine these flocks and control the spread of the disease, Pabilonia said. In the wild, officials have little or no control.
The virus spreads easily among some species of geese as well as raptors that feed on infected birds, Pabilonia said.
As bird flu spreads among wild creatures, it also evolves, Pabilonia said. The virus is decades old and has changed many times over the years. Some variants jump into mammalian species.
In Colorado, a mountain lion, black bear and skunk have all been confirmed to have contracted the virus. Duncan said wildlife officials are testing many more animals for the virus, although he could not say how many test results remain outstanding.
“The lab has a pretty steady stream of animals going through autopsy as well as swabs or other samples collected from the field,” Duncan said. “That number would change daily.”
Dogs and cats could be susceptible to the virus, Pabilonia said. Particularly in the Front Range, which has a higher concentration of people and pets than rural Colorado. But so far no dogs or cats have been reported to have contracted the virus, she said.
Pet owners should be aware of the risk, but Pabilonia does not recommend any major lifestyle changes. People who own dogs and cats should already avoid letting their pets interact with wildlife in general and the outbreak of bird flu highlights the importance of this rule, she said.
Similarly, humans can also catch the virus, but that’s relatively rare and unlikely, Pabilonia said.
“But that doesn’t mean we shouldn’t pay attention to it,” she added. “Generally, we never want an uncontrolled organism to spread through animal populations.”
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