An equine flu outbreak that killed 146 feral horses may have caused more severe illness due to vaccination delays, concurrent bacterial infections and previous lung damage.
The deaths occurred in April and May at the Wild Horse Off-Range Corral of the Bureau of Land Management at Canon City Correctional Facility in Colorado. A joint Incident Review Team from the BLM, Colorado Department of Corrections, Colorado Correctional Industries, and Colorado State Veterinarian’s Office has since written a report published in July on how the deaths occurred and how to prevent future high-mortality events.
The Canon City facility was home to around 2,550 horses, but severe flu and deaths have mostly occurred among around 450 horses that were removed in the summer of 2021 from the West Douglas range in western Colorado, where the fire had damaged their habitat, according to reports from the BLM and Colorado State Veterinarian’s Office. The horses arrived at the facility in July and August 2021.
Workers at the Canon City plant found nine of the West Douglas horses dead on April 23, and 46 more would die or be euthanized within two days. Diagnostic test results revealed the horses had been infected with an H3N8 equine influenza virus, which the tests identified in nasal swabs and lung tissue.
Investigators found that influenza infections were complicated by co-infections with Streptococcus equi subspecies zooepidemic. The horses’ lungs may also have been compromised by wildfire smoke and a dust storm, “making horses particularly susceptible to complications from equine influenza,” the joint report states.
“Finally, the group of affected horses have a consistent and uniform phenotype and may be genetically very similar,” the report states. “This and the specific range over which these horses occupy, i.e. quite isolated from potential contact with domestic equids, may play a role in the increased susceptibility of this group and higher than normal mortality for such an epidemic.”
Although most of the horses at the facility had been vaccinated against influenza within the previous six months, horses at West Douglas were all unvaccinated, partially vaccinated or receiving booster shots within 10 days of the outbreak, according to the BLM reports.
The joint report indicates that vaccination generally begins within 30 days of arrival. A refrigerator malfunction early in the summer had compromised some of the facility’s vaccines, and the facility manager, in consultation with the attending veterinarian, decided to keep the vaccines available to give boosters to others. horses, as West Douglas horses would at least be housed in corrals. 180 meters further.
Horses arriving later from a herd with an avid following were overtaken by West Douglas horses in priority for vaccination and other preparations for adoption, and another group of horses shipped from Wyoming received attention priority upon arrival due to an agreement between BLM and the Colorado State Veterinarian’s Office that horses be immediately tested for equine infectious anemia because they had been shipped across state lines without being tested.
The review team recommended that the BLM implement a policy on the timeliness of vaccination of newly rounded wild horses and burros and that agency officials consider a facility’s current capabilities when planning. assembly and movement of animals. The team’s report also echoes previous findings by BLM officials that the Canon City facility was understaffed – affecting animal care, facility maintenance and record keeping – and the report recommends that refrigerators used to store vaccines be equipped with temperature monitoring devices that signal when cooling systems fail. .