The Humane Society of the United States is raising concerns about the potential for wild horses in the West to contract an equine herpes virus from domestic horses.  The society urged the Bureau of Land Management in a letter on Thursday to discourage and, where appropriate, prohibit private horse owners from bringing potentially exposed horses onto federal lands. Holly Hazard, the group's chief innovations officer, says there's the potential for a catastrophic outbreak of the virus among wild herds. She says the agency needs to treat the threat as an emergency beginning with public education. BLM spokesman Tom Gorey says no animals managed by the agency are known to be infected. He says BLM is considering limiting horse movement on a case-by-case basis and may cancel some scheduled adoption events.