Transmission of chronic wasting disease among deer is "remarkably efficient," according to a new study by a University of Wyoming researcher and her Colorado colleague.

Published in today's edition of the science journal Nature, the research paper by UW's Elizabeth Williams and Mike Miller of the Colorado Division of Wildlife contends that the disease is spread animal to animal rather than from mother to unborn fawn.

"It is important to know as much as possible about transmission when attempting to control a disease, because that information helps guide management approaches," Williams said in a telephone interview from her Laramie laboratory. Williams is credited with first identifying chronic wasting disease as a graduate student 25 years ago.

Chronic wasting disease is a member of a larger class of diseases called "transmissible spongiform encephalopathies," or TSEs.

TSE diseases have been found in sheep, where the disease is scrapie; deer and elk, where it's chronic wasting disease; mink; cats; squirrels; monkeys; humans, where it's called Creutzfeld-Jakob disease; and other species, such as zoo animals.

Once found just in a small area on the Colorado and Wyoming border, chronic wasting disease has spread through elk ranches and wild deer herds as far away as Wisconsin and Canada.

"It really isn't that earthshaking," Williams said. "We knew just from observing our test animals that it was spreading horizontally." The research refutes the earlier belief that the transmission of the disease from doe to fawn had played an important role in the spread of the disease.

That belief, popular among scrapie researchers, led sheepmen to kill dams and their offspring - entire bloodlines - to halt the spread of the disease.

"What our research shows is that in a captive situation like a game farm, that approach isn't going to work," Williams said. Even separating offspring from mothers isn't going to help that much, she said, because transmission happens by environment. The research won't help managers of free-ranging deer, she said, but it does have implications for managers of game farms.

"They really can't try to break the maternal-offspring transmission and think that that's necessarily going to take care of the problem," she said.

Williams and Miller studied two groups of captive mule deer at a research center in Colorado. The first set of deer were born-to-captivity does that had contracted the disease. The second group was born in the wild and free of the disease, later captured and placed with the first group after they were weaned at 14 weeks.

All of the animals eventually contracted the disease, wrote Miller and Williams.

Fawns born to infected mothers were as likely as those born to uninfected mothers to contract the disease, Miller said. "Deer-to-deer (as opposed to strictly doe-to-fawn) transmission seems to be primarily responsible for perpetuating outbreaks," he said.

Concentrations of animals, in captivity or in the wild, probably encourage the spread of the disease, Miller said, as has the interstate shipment of infected animals.

Williams and other researchers are running experiments to see if transmission of the disease is associated with ingestion of saliva, urine, blood or feces, animal to animal. One ongoing experiment is to take CWD-free deer and expose them to the feces of infected deer.

Deer don't deliberately eat each others' feces, Williams hastened to explain, but deer pellets break down and the material can blow or wash up on forage. Biologists know that certain parasites are spread in this manner, she said, so it shouldn't be surprising if the tough and mysterious "prion" thought to be responsible for the disease can spread in a similar manner.

Scientists believe that a naturally occurring strand of nerve cell protein called a prion is responsible for the TSE diseases. Prions in their natural shape are benign, but problems develop when a prion strand becomes abnormally bent and twisted. In a way that scientists have yet to figure out, a "bent" prion can cause surrounding prions to bend the same way.