Virus likely the cause of death of 95 wild horses

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 last week and said at least 57 horses had died since the weekend in Cañon City, Colorado, 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 waystation 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 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 spokesperson for the bureau, said 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.