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CAÑON CITY, Colo. – Bronchopneumonia caused by the influenza virus and strep zooepidemicus bacteria caused the high mortality among horses at the Bureau of Land Management’s Wild Horse and Burro Corrals located on the Colorado Department of Corrections East Canon Complex in Canon City, CO confirming earlier results these infectious agents contributed to the deaths of 145 horses since April 23.

A review team including staff from the Colorado State Veterinarian’s Office, the Colorado Department of Corrections and the Bureau of Land Management have begun a review of the events surrounding the outbreak at the Canon City facility to identify ways to help prevent and mitigate future disease outbreaks. The BLM’s Comprehensive Animal Welfare Program Compliance Assessment Team last week reviewed the facility’s compliance with BLM’s animal welfare standards for off range corrals. The results of the BLM review are available online at Bureau of Land Management | Compliance Assessment.

“This review will allow us to better understand management factors that may have contributed to this outbreak so we can better understand how to avoid another outbreak,” said BLM Colorado Acting State Director Stephanie Connolly. “We are encouraged by the improving health of the West Douglas horses and the cooperation between the BLM and the State of Colorado in responding to this outbreak.”

“Diagnostic testing of samples obtained from horses that were autopsied on the first few days of the outbreak has been completed. Microscopic examination of the tissues has confirmed the cause of the high mortality disease outbreak as bronchopneumonia characterized by severe acute pulmonary edema, hemorrhage, necrosis and suppurative processes. These finding are consistent with the previously identified H3N8 equine influenza virus and streptococcus equi subspecies zooepidemicus infections,” said Dr. Albert Kane, a veterinary epidemiologist with the US Department of Agriculture who works as an advisor to the BLM Wild Horse and Burro Program.  

“Virus isolation, DNA sequencing and additional laboratory investigations to better understand the host, agent and environmental factors that contributed to the unusually high mortality seen among the West Douglas horses are ongoing. It is anticipated that it could take several weeks or months to complete this second phase of the outbreak investigation,” he said.

The voluntary quarantine of the facility will remain in place at least until July 1, 2022. During this time enhanced disease surveillance and monitoring will include regular visits to the facility by the attending veterinarians. Veterinarians and epidemiologists with the US Department of Agriculture and the Colorado Department of Agriculture including the State Veterinarian of Colorado will continue to monitor the situation and advise the BLM during the quarantine period and take measures to reduce the risk of similar outbreaks occurring in the future.

The veterinarian reports, situation reports and updates on the facility can be found online at https://www.blm.gov/programs/wild-horse-and-burro/herd-management/herd-management-areas/colorado