Chronic Wasting Disease

By CONNIE MERTZ

It’s like a scene from a science fiction movie: A strange, alien disease is invading North America to which there is no known vaccine or cure, and while researchers are scurrying about to uncover scientific data about its potential dangers, cervids (members of the deer family) are at risk, and though medical research so far finds it unlikely that the disease can be transmitted to humans, it has yet to be proven.

This dilemma is not on the movie screen—it is reality. Called Chronic Wasting Disease (CWD), it is defined by the Chronic Wasting Disease Alliance as “a transmissible neurological disease of deer and elk that produces small lesions in brains of infected animals and is classified as a spongiform encephalopathy (TSE).” So far, scientific studies have shown CWD to be neither a bacteria nor a virus, but is theorized to be caused by prions, infectious proteins without associated nucleic acids.

Mule deer in northern Colorado were the first to be detected with CWD in 1967, mainly in captive deer herds. However, since the mid 1980s, it has been identified in free-ranging deer and elk in Colorado, Wyoming, Nebraska, South Dakota, Wisconsin, Minnesota, Illinois and New Mexico. The alarm is sounding as more and more states, including Pennsylvania, recognize the potential dangers of CWD.

“We are checking for CWD,” said Jerry Feaser, press secretary for the Pennsylvania Game Commission. “During the 2001 elk season, as part of the blood and tissue samples we collected from a variety of tests, we tested all hunter-killed elk for CWD, and all tests came back negative,” he affirmed.

Tests are ongoing. This past season samples were taken from 61 harvested elk and more than 500 harvested deer, and tests are due back around the end of January.

Feaser points out that there is no known vaccine or cure for CWD. “Prevention is the only practical and preferred option.” To complicate the situation from a management perspective, he said, “The most important management challenge is that there is no practical live animal test.” What is required for testing is the extraction of the brain stem. Another management challenge lies with the disease itself. “CWD has a long incubation period of more than a year without showing clinical signs of being infected, which allows the animal to spread the disease without detection, and there’s the possibility of environmental contamination,” stressed Feaser.

Symptoms occur most in adult animals, and are progressive and always fatal. The most obvious sign is loss of weight, and as the disease lingers, animals become listless and develop unhealthy behavioral habits like excessive salivation and teeth-grinding, with an increased thirst. According to information from the U. S. Department of Agriculture, “the origin and mode of transmission of CWD is unknown. Animals born in captivity and those born in the wild have been affected with the disease.”

It is important to emphasize that there are no known cases of CWD in the state of Pennsylvania, and both the Pennsylvania Game Commission (PGC) and the Department of Agriculture are working together to keep it this way. It is believed the most likely way that CWD would spread into the state is through importing cervids, deer and elk in particular, from other infected areas. In all, there are 700 deer propagators and 90 elk propagators in Pennsylvania.

As of August 1, 2002, the Game Commission banned importing live cervids into Pennsylvania. However, deer and elk farmers can legally export their animals to other states. To date, about 20 other states have banned the complete importation of cervids.

What would the PGC do if they discovered CWD? “The likely plan of action will involve finding the specific area in which a “hot” deer was taken. We then would want to conduct a more extensive sampling of the deer in that area,” volunteered Feaser.

While there is no proof that CWD can be transmitted to humans under normal conditions, both the Center for Disease Control and the World Health Organization recommend that venison should not be eaten from a CWD-infected animal. Anyone who observes any cervid with symptoms of CWD is asked to contact one of the Commission’s offices throughout the state.

The Pennsylvania Game Commission is already alerting hunters to the potential of CWD through news releases and brochures as well as having a CWD section on their website. “We must be careful that we don’t unnecessarily alarm hunters since we don’t have any suspected cases of CWD in Pennsylvania, but we do have a responsibility to make them aware of what we are doing to prevent CWD from coming to PA and how we plan to respond should CWD be identified,” said Feaser.

“Until it is known how contagious CWD is and how it is spread, we are all sweating,” said one unidentified deer farmer in Pennsylvania.

For more information, check the Chronic Wasting Disease Alliance’s website at www.cwd-info.org.