DENVER – Officials believe a strain of equine influenza could be to blame for the death of what as of Thursday is 95 wild horses this week at a Bureau of Land Management corral in Cañon City.
The 95 horses have all died at the BLM Wild Horse and Burro Corrals, located on the Colorado Department of Corrections East Canon Complex, since April 23, according to the BLM.
The bureau said it sent PCR lab tests to two top veterinary labs in the U.S., which identified the likely cause of the respiratory outbreak and deaths as H3N8 equine influenza, which the BLM says is “not uncommon” in both wild and domesticated horses.
The BLM said the group of horses that are dying have all come from a group called the “West Douglas horses” – which were rounded up in August 2021 after the Oil Springs Fire burned about 12,000 acres south of Rangely, Colo., last June.
The BLM said no other horses out of 2,184 others at the facility had died as of Thursday despite 10-20% of them showing “more typical mild clinical signs of influenza.”
Most of the horses at the corral are in good condition, according to a report written by Dr. Albert Kane, with USDA APHIS Veterinary Services in Fort Collins, which says that problems first appeared to start about 5-10 days after a group of about 50 horses received vaccinations, and that those horses appeared to have the most severe outcomes at the start.
The BLM said PCR tests had also identified two different equine herpes viruses – EHV-2 and EHV-5 – but that it was unclear how those viruses might be contributing to the severity of the influenza in the West Douglas horses.
“Underlying reasons the West Douglas horses are so severely affected compared to other cohorts on the same premises are uncertain but could include previous exposure to smoke inhalation during the wildfire that prompted their capture and removal, unvaccinated or partially vaccinated status, exposure to extremely dusty conditions at the north edge of the facility, compromised immune system possibly due to a toxic plant or other exposure,” the report says.
“The Bureau of Land Management will review operations at the Canon City facility to prevent future outbreaks like this from occurring,” BLM Colorado Acting Associated State Director Ben Gruber said in a statement. “This tragic outcome was influenced by a population of horses that may have been particularly vulnerable given their time in the West Douglas area and their exposure to last year’s wildfire that prompted their emergency gather.”
Colorado Department of Corrections Executive Director Dean Williams said the DOC and BLM were trying to stem the spread of the virus and hoping to prevent similar things from happening in the future.
The BLM says the corral is under a voluntary quarantine, meaning no horses are allowed to leave for the foreseeable future until officials can determine the horses are healthy and don’t pose a risk to other horses.
The bureau said in addition to working with the diagnostic lab veterinarians, it was working with others from the U.S. Department of Agriculture and the Colorado State Veterinarian’s Office to figure out and mitigate the reasons some of the horses are seeing fatal cases.
Among the recommendations issued in the report were added cleaning and disinfecting procedures for trucks and equipment and bringing in a separate loader to handle the carcasses of the dead, and further sampling for more clinical signs of disease.
BLM first reported the incident Tuesday, saying the facility was under a voluntary quarantine due to an "unknown yet highly contagious" disease outbreak.