A disease outbreak that has killed more than 140 horses at a federal facility in Cañon City is slowing, officials said this week, and evidence suggests equine flu, streptococci and environmental factors likely all contributed to the spike in death.
One hundred and forty-four horses from the Cañon City Wild Horse and Burro Facility have died since April 23, according to situation reports released by the Bureau of Land Management. The cause appears to be a combination of diseases, and environmental factors such as wildfires and high winds may also have played a role.
The good news is that the outbreak may be resolving itself: No deaths were reported on Tuesday or Thursday this week, the first days without deaths since the outbreak began.
“Clinical observations” earlier this week “suggest that the horse population across the facility, including those in the severely affected West Douglas subpopulation, is returning to normal,” officials wrote. of the Bureau of Land Management. These observations, the report continues, “suggest that the epidemic is diminishing in intensity and beginning to resolve.”
Now officials are working to better understand what exactly led to the sudden and intense deaths among a particular herd at the facility.
When the first 10 horses died three weeks ago, state veterinarian Maggie Baldwin said, the initial veterinary evaluation suggested the cause was neurological. Further monitoring of the herd revealed “significant respiratory disease,” she told members of the governor’s expert panel on emergency outbreak response.
“There were a lot of horses that died in a very short time,” she said.
Diagnostic tests sent to Colorado State University and the University of California, Davis have tested positive for equine flu, she said. Equine flu can infect and sicken a large portion of a herd, but it usually has a low mortality rate, Baldwin said, which made the rush of deaths unusual. Strep Zoo was also discovered in the dead animals, which further aggravated the condition of the horses.
There are about 2,600 horses at the Cañon City facility, but the outbreak was particular to the West Douglas herd. The horses had been pulled from a wildfire area last year, Baldwin said, and they may have been “prone to lung damage” from the smoke. Mortality among the West Douglas herd exceeded 25%, she said. Between 40% and 60% of horses in the herd had symptoms, compared with about 20% of horses in other paddocks, according to the situation report from the Bureau of Land Management.
Additionally, specifically affected parts of the herd had been removed from wildfire areas last year, and there had been “significant wind and dust issues” in the herd area in the weeks leading up to the outbreak. , Baldwin told a committee of Colorado medical experts on Thursday.
The deaths were caused by a “complex outbreak of multifactorial respiratory disease involving the H3N8 equine influenza virus and the bacterium” that causes zoo streptococcal disease in animals, the Bureau of Land Management wrote. Diagnostic labs are still working to determine the influence of these environmental factors, Baldwin and the federal agency said.