Nearly 120 horses have died at BLM facility in Colorado

According to, equine influenza is ravaging a Bureau of Land Management herd in Fremont County, Colorado. In a May 3 report, the BLM confirmed 119 mustangs have died from the disease in Canon City, Colorado.

Clinical signs of this respiratory condition are characterized by mild/moderate fever, coughing or nasal discharge, depression, and labored breathing.

The first four dead horses were found April 23 in pens containing horses gathered from the West Douglas Herd Area in July and August of 2021. According to the report, at this time several horses were gravely ill and “showing signs initially thought to be neurologic” but later attributed to hypoxia from severe pneumonia. Over the next three days about two dozen horses died or were euthanized for severe debilitating respiratory distress in the West Douglas group of horses. Post-mortem examinations consistently found pneumonia characterized by severe pulmonary edema and hemorrhage.”

Morbidity characteristics were noted in 40% to 60% of the West Douglas horses, and PCR tests of blood, swabs and tissues for EHV- and -4 were consistently negative. However, the report states, “several nasal swabs and lung tissue specimens tested positive for equine influenza, confirmed to be H3N8 by PCR testing.”

Officials attribute the history of the West Douglas horses gather and removal from the range because of a wildfire in their herd area, plus severe winds, dust storms and other factors in the current area prior to the outbreak.

“The West Douglas horses had been in the facility for about nine months but are still unsettled, flighty as a group and easily disturbed in the pens,” the release said. “Most of the facility population is current (within six months) for flu/rhino vaccination, however the West Douglas horses in pens 40-43 are either unvaccinated, have only received one shot, or only recently received their booster shots about 10 days before the outbreak.”

Further testing of the samples positive for the equine influenza virus has determined the virus to be the Florida Clade 1 sublineage. This is currently the endemic strains of equine influenza in North America.

According to the BLM situation report from May 2, the plan of action is to:

• In addition to the voluntary quarantine of the entire facility, supportive care for affected animals and biosecurity measures have been put in place.

• Animals that could be handled without being moved outside the most affected pens were provided with anti-inflammatories or antibiotics at the direction of the attending veterinarian. Most of the affected animals are wild and ungentled and cannot be treated without use of the hydraulic squeeze chute systems. This risks further spreading the illness throughout the facility, stressing the animals that could exacerbate any current underlying issues and risk further injury to adults and young foals in the affected pens. For these reasons, individual animal treatment will be limited.

• The preventive medication of water with antibiotics is considered, but not implemented at this time.

• Dust mitigation efforts including wetting down adjacent roads and gravel areas is being done on an ongoing basis.

For more information on the outbreak visit or the Colorado Department of Agriculture website at

Kylene Scott can be reached at 620-227-1804 or [email protected].