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Wild horses at the East Cañon Correctional Complex on October 13, 2021, in Cañon City. (Hugh Carey, The Colorado Sun)

Veterinarians say a highly contagious equine flu has killed 95 wild horses so far this week at federal Bureau of Land Management holding pens in Cañon City. 

The mustangs captured from Colorado rangeland and hauled to the federal facility on state prison grounds have been dying at a rapid pace. Federal officials first announced the deaths on Monday, saying 57 horses had died in the prior three days. By Thursday night, the tally was at 95. 

Most of the dead mustangs were from the West Douglas range, in far western Colorado along the border with Utah. Those horses might be particularly vulnerable to the influenza because they were exposed last year to a wildfire, which prompted their emergency roundup, said the BLM’s acting associate state director, Ben Gruber. 

He vowed that the federal agency will “review operations” to prevent future outbreaks, calling the outbreak a “tragic outcome.” 

Veterinarians, including from Colorado State University and the U.S. Department of Agriculture, have been investigating the deaths all week, using nasal swabs and lung tissue from several horses, the BLM said. Two veterinary labs confirmed the equine influenza, which is not uncommon among wild and domestic horses, the BLM announced Thursday. The flu is not related to the current outbreak of avian flu affecting birds and poultry, which, officials confirmed Thursday, had infected a Colorado man.

Lab testing also found two equine herpes viruses, also common in horses, the BLM said. But it was unclear whether those viruses were contributing to the high death rate. 

About 10-20% of the 2,184 mustangs in the Cañon City corrals are showing mild signs of the respiratory influenza virus. Those horses are not from West Douglas and none have died. They are separated from the horses with more severe illness.

Wild horses grazing on public lands on Wednesday, Sept. 1, 2021, near the Sand Wash Basin outside Craig. (Hugh Carey, The Colorado Sun)

CSU veterinarians and the U.S. Department of Agriculture are continuing to investigate. The facility is under quarantine and no horses are leaving the premises “for the foreseeable future,” the BLM said. 

Meanwhile, mustang advocates are pointing to the deaths as a failure of the federal wild horse and burro program, which has plans to round up another 19,000 horses in the next year. The animals are held in facilities across the country before they are released for auction and adoption. National wild horse groups have called on Gov. Jared Polis and First Gentleman Marlon Reis, an animal rights advocate, to step in to help stop helicopter roundups and overcrowded holding pens. 

In a Facebook post Thursday, Reis said that he and Polis’ staff have talked to officials at the state Department of Agriculture and that he planned to work to prevent future deaths. 

“There is a very important conversation to be had once this crisis is contained about how this happened and what needs to be done to ensure it doesn’t happen again,” he wrote. 

The facility on the grounds of the Colorado Department of Corrections was the new home for 450 mustangs removed last July and August from the West Douglas range. It also has several hundred horses from a large-scale helicopter roundup conducted last year in the Sand Wash Basin in far northwestern Colorado, along the border of Wyoming. Nearly 700 horses were herded by a low-flying helicopter into holding pens during the two-week roundup in Sand Wash in September.

Jen is a co-founder and reporter at The Sun, where she writes about mental health, child welfare and social justice issues.

Her first journalism job was at The Hungry Horse News in her home state of Montana, before moving on to reporting jobs in Texas and Oklahoma. She worked for 13 years at The Denver Post, including several years on the investigative projects team, before helping create The Sun in 2018.

Jen is a graduate of the University of Montana and loves hiking, skiing and watching her kids' sports.

Email: Twitter: @jenbrowncolo