Chronic wasting disease is transmitted more easily than previously thought, a finding that complicates efforts to curb the relative of mad cow disease as it spreads in populations of deer and elk, according to a new study.

Researchers who previously believed transmission from doe to fawn played an important role in its spread now say that¹s not the case. Instead, the contagious brain disease is ³remarkably efficient² at spreading from animal to animal, new research shows.

The finding suggests it will be harder to control the fatal disease other than through the drastic thinning or eradication of infected herds, as has happened in parts of Wisconsin.

³Unfortunately, that¹s what we¹re left with in the short term. In the long term, we hope something will come along,² said Mike Miller, of the Colorado Division of Wildlife and co-author of the new study.

Details appear Wednesday in the journal Nature.

Researchers believe the disease spreads in deer and elk when they encounter infected feces or saliva. Concentrations of the animals, whether in the wild or in captivity, likely encourage its spread, as has the interstate shipment of infected animals, Miller said.

There is no evidence the disease infects either livestock or humans.

Miller and co-author Elizabeth Williams, of the University of Wyoming, Laramie, studied two populations of captive mule deer at a research center in Colorado. One set was born-to-captivity does that had contracted the disease. The second was born in the wild deer free of the disease, but later captured and placed with the first group when 14 weeks old.

All of the animals in both groups eventually contracted the disease, which discounted the theory that maternal transmission was key to its spread, Miller said.

Judd Aiken, of the University of Wisconsin-Madison, said the study was important but its results were unsurprising.

³It provides further support of what¹s been apparent, that CWD is a contagious prion disease,² Aiken said, referring to the modified proteins thought to cause the disease.

The disease affects the nervous system and is marked by weight loss, stumbling, tremors and lack of coordination. There is no cure.

Chronic wasting disease was first identified in 1967. Until several years ago, researchers thought the disease was restricted to animals living in a small region straddling Colorado and Wyoming. It has since been found in several neighboring states and Canada.