An equine influenza virus likely caused the mysterious respiratory disease that has killed at least 95 wild horses and forced a federal holding facility in Colorado to go under quarantine, the Bureau of Land Management said Thursday.
Tests showed that a strain of the virus, known as H3N8, was likely the cause of the outbreak and related horse deaths, the bureau said in a news release, adding that the virus is “not uncommon” among horses.
The identified strain is not related to a bird flu outbreak this year in the United States, officials said.
The bureau, which is in charge of caring for the nation’s wild horses, announced the outbreak on Monday and said at least 57 horses had died since the weekend in Cañon City, Colo., more than 100 miles south of Denver. The number of deaths reached 95 by Thursday.
It’s the second time in recent weeks that the bureau had to shut down a facility because of a widespread illness among horses. In late March, a facility in Wyoming was closed and an adoption event for wild horses was postponed because some animals developed Streptococcus equi, a bacterial infection similar to strep throat.
The recent deaths are part of a larger struggle to sustainably manage wild horses and burros in the West. There are about 86,000 animals roaming public lands, more than three times what the bureau says lands can support.
In an attempt to keep populations in check, the bureau rounds up thousands of horses every year and offers them for adoption. But the number of people willing to adopt an untrained mustang has almost never equaled the number of animals the government removes, so a surplus has built up year by year in a collection of corrals and pastures that the bureau calls “the holding system.”
The system now holds more than 60,000 animals at a cost of about $72 million a year.
The holding system includes long-term ranches in the tall grass prairie where unwanted horses can spend decades, as well as short-term feedlots where crowded corrals temporarily hold horses fresh off the range.
The short-term facility in Cañon City sits next to a Colorado state prison, where inmates train horses. It acts as a way station where animals from different herds that roam over 33 million acres of open range in the West are brought together in corrals that cover only about 50 acres, making it a potential breeding ground for disease. It is meant as a temporary stopover, but because of overcrowding in the holding system, horses often stay for many months.
The bureau said on Monday that there were 2,550 horses in Cañon City’s dusty maze of corrals — just a few hundred shy of its 3,000 maximum.
Steven Hall, a spokesman for the bureau, said on Thursday that the facility would remain under quarantine “as long as necessary” to prevent the spread of the virus.
Most of the horses affected by the disease were removed last year from a swath of sage-dotted mesas in northwestern Colorado known as the West Douglas Herd Area, officials said. That roundup was done to protect the health of the horses, the rangeland and public land from overuse by excess horses, the bureau said. At the time, a portion of the herd was tested for a potentially fatal virus called equine infectious anemia, which can spread through fly bites. Though all the tests were negative, the West Douglas horses were temporarily kept separate from other horses, according to the bureau.
“This is the first situation that I’m aware of that so many horses died so quickly and so suddenly,” Scott Beckstead, director of campaigns for the Center for a Humane Economy, a nonprofit animal welfare organization, said on Wednesday.
Mr. Beckstead said he thought the outbreak was an indication that the conditions in the holding facilities were too crowded and filthy. “We’ve seen photographs of the horses at Cañon City,” he said. “It’s cramped. The horses are standing closely together. It’s just a perfect environment for disease to spread.”
Suzanne Roy, executive director for the American Wild Horse Campaign, said in a statement on Wednesday that the bureau was putting the animals in harm’s way. “These are not livestock,” she said. “They are an iconic and federally protected wildlife species.” Ms. Roy also called for a full investigation into the bureau’s off-range wild horse holding system.
The bureau has been under pressure for decades by both horse-advocacy groups and lawmakers to shrink the size of the holding system. That has led to repeated scandals, in which thousands of protected wild horses were adopted out of the system only to immediately end up at slaughter houses.
In 2019, the bureau began paying adopters $1,000 a head to take animals off its hands. Adoptions have nearly tripled since the program started, but an investigation by The New York Times showed a large number of those horses were sold to slaughter buyers almost as soon as the checks cleared.
Despite increased adoptions, the number of horses stored in the holding system has only grown, increasing by about 10,000 since 2020, partly because of an increase in roundups.
The bureau has proposed doubling the number of animals it rounds up each year, to about 20,000, in an attempt to limit populations on the range, but the move would drastically increase the number of horses in the system.
“The United States government is on a campaign to remove large numbers of these federally protected animals to benefit the private live stock industry,” Mr. Beckstead said. He advised that, in the short term, the bureau should halt the mass roundups until heathy and safe conditions can be guaranteed.
“The federal government is going to cost the American taxpayer tens of millions of dollars to round up tens of thousands of wild horses,” he said. “It’s a financial boondoggle because the cost of caring for those animals is going to be astronomical and it would be far cheaper to leave them on their designated habitat and manage them there on the range.”