LINCOLN, Neb. – The number of Nebraska deer testing positive for chronic wasting disease fell for the second year in a row, although there is evidence the disease has expanded.

Seventeen deer tested positive, out of a sample size of 5,841, for the disease in 2006, according to Bruce Trindle, fish and wildlife specialist for the Nebraska Game and Parks Commission’s Norfolk office. The state, which began sampling deer in 1997, had a high of 33 positive tests in 2004 and 19 the following year.

Three positive tests came from deer taken in northeastern Cherry County, where there had been one positive in 2004. Of the 114 positive tests statewide since the program began, most have come from deer taken in Panhandle counties.

However, some areas that have had a concentration of positive tests since the program began – such as northern Sioux County and the southwestern Panhandle counties of Scotts Bluff, Banner and Kimball – showed just one positive test among them.

“We are encouraged by the lack of positives in areas where there have been concentrations in previous years,” Trindle said. “This does not mean the disease is being controlled in these areas, but more that the frequency is remaining low.”

Chronic wasting disease (CWD) is a disease that attacks the central nervous system and causes fatal damage to the brains of white-tailed deer, mule deer, moose and elk.

CWD is a prion disease similar to mad cow disease. A prion is a mutated protein in the body that causes other normal proteins to fold abnormally and cause sponge-like holes in the brain.

CWD is transmitted from animal to animal, probably through body fluids such as feces, urine, or saliva. Animals that are crowded or confined have a greater chance of encountering the body fluids of other animals and, therefore, a higher likelihood of becoming infected if the rogue prion is present. Animals that have a social system that includes close contact with herd mates also may have a higher chance of becoming infected. Recent research indicates that CWD prions can survive in the environment after infected and exposed animals are removed. CWD is not known to affect humans.

Here’s a breakdown of the 17 positives tests in Nebraska last year: hunted mule deer, nine; hunted white-tailed deer, six; culled mule deer, two.

Deer testing positive came from the following counties: Sheridan (seven), Dawes (four), northeastern Cherry (three), Cheyenne (one), Sioux (one), and Box Butte (one).

Trindle said the successful testing program is possible only because of the hunters who voluntarily allowed their deer to be tested.