Report detailing factors in 146 wild horse deaths released

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In April and May of 2022, 146 wild horse deaths were reported at the Bureau of Land Management’s Wild Horse Off-Range Corral (BLM) at the Canon City Correctional Facility in Colorado. After a joint incident review from the Colorado of Corrections, Colorado Industries, Colorado State Veterinarian’s office, and BLM, a report was created and released on the deaths and how to prevent other high-mortality events caused by equine influenza.

The Canon City facility, which has 2,550 horses, had to remove around 450 horses during the summer of 2021 from the West Douglas ranch in western Colorado because of fire damage to their habitat. All of the transferred horses arrived in July and August of 2021.

According to a release from the American Veterinary Medical Association,¹ starting on April 23, workers at the facility discovered 9 West Douglas horses deceased, followed by 46 either dying or euthanized within the next 2 days. After tests, including nasal swabs, and on lung tissue, were conducted, the results showed that the horses had the H3N8 equine virus.

“Lastly, the affected group of horses have a consistent and uniform phenotype and may be genetically very similar,” stated the report.² “This and the specific range on which these horses occupy, i.e. fairly isolated from potential contact with domestic equines, may play a role in the increased susceptibility of this group and higher than normal mortality for such an outbreak.”

According to the release,¹ investigators studying the deaths believe the infections were complicated by coinfections with Streptococcus equine subspecies zooepidemicus, and that the horse's lungs could have been compromised by the wildfire smoke and a dust storm. A factor that made the animals more susceptible to equine influenza complications.

Upon further review, the report also discovered most horses at the facility received the vaccination against influenza 6 months before this incident, but all of the West Douglas horses were either unvaccinated, partly vaccinated, or received a booster shot within 10 days of the equine influenza outbreak. The report also discovered that although vaccinations begin within 30 days of the horse’s arrival, a refrigerator malfunction compromised some of the BLM's vaccinations.

After discussing with the attending veterinarians, the facility manager chose to hold the available vaccinations to administer boosters for other horses because the West Douglas horses were to be housed in corrals at least 180 yards away. The horses were also once again passed for vaccination by those being prepped for adoption as well as horses that arrived from Wyoming. The Wyoming horses were bumped ahead because they were shipped across state lines without being tested, a decision made by both the Colorado State Veterinarians’ office and the BLM.

After the review, the team recommended that BLM create a policy on how quickly new wild horses and burros should be vaccinated and install a temperature monitoring device in its refrigerators to alert staff if the cooling system fails.

Reference

1. Bureau of Land Management report details factors in 146 wild horse deaths. American Veterinary Medical Association. Accessed August 4, 2022. https://www.avma.org/news/bureau-land-management-report-details-factors-146-wild-horse-deaths?utm_source=delivra&utm_medium=email&utm_campaign=todays-headlines-news
2. Report on the high-mortality incident at the Canon City off-Range Corral in Canon City, Colorado April-May 2022. Blm.gov. Accessed August 4, 2022. https://www.blm.gov/sites/default/files/docs/2022-07/Canon%20City%20Review.pdf