'Zombie deer' threatening to invade US state

It may sound like the setup for a low budget horror film, but wildlife officials have warned of the genuine threat of zombie deer.

Regulators are working overtime to stop the afflicted animals from reaching Nevada, worried that the chronic wasting disease that gives them their name could make them a danger to humans.

The highly contagious terminal illness has been compared to mad cow disease in cattle and makes the deer lethargic and extremely weak - but also neutralises their usual fear of people.

It is transmitted by protein particles that cause irreparable damage to brain tissue, and has the potential to wipe out entire populations of deer, moose and elk.

Dead animals are being tested for signs of the disease in Utah, which borders Nevada, and cases have already been reported in Kansas, Colorado and Wyoming.

The national health protection agency, Centers for Disease Control and Prevention, believes the virus could be a risk to humans, with protein particles having been linked to the similarly degenerative Creutzfeldt-Jakob disease.

According to a study by the Center for Food Security and Public Health, symptoms take at least 16 months to reveal themselves after exposure and the average incubation period is two to four years.

Some research has indicated that animals can be contagious before symptoms begin, and the disease can also remain present in the environment for years.

Earlier this year, Nevada brought in a law banning certain animal parts - including the brain and spinal cord - from being brought into the state because of the high concentration of prions.

Tyler Turnipseed, chief game warden in Nevada, had posed a scenario where local populations could be infected by butchered waste dumped by a hunter passing through from another state.

Despite restrictions being introduced, officials have acknowledged it may be impossible to prevent the disease from getting into the state.

Peregrine Wolff, a Nevada wildlife department veterinarian, said: "It's not a matter of if, it's a matter of when. We know that we can't wrap Nevada in a bubble."