Guidelines created to increase safety of venison; Remove tissues where prions concentrate

September 8, 2002 Milwaukee Journal Sentinel by Bob Riepenhoff
Wisconsin is preparing for a fall deer hunt like no other in history.

The discovery of chronic wasting disease in wild deer west of Madison has raised questions about the safety of eating venison.

A poll conducted for the Milwaukee Journal Sentinel showed that more than 60% of people who have eaten Wisconsin venison in the last five years are unlikely to eat venison now.

The concerns linger as the first of Wisconsin's deer hunting seasons -- the early archery season -- gets under way Saturday, Sept. 14.

While no one is guaranteeing the safety of Wisconsin venison, state food experts say hunters, as well as commercial meat processors, can greatly reduce any risk by following some simple guidelines developed by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP). The guidelines were established to help hunters and butchers avoid those tissues where prions -- the abnormal proteins believed to cause the disease -- concentrate. Prions are not affected by cooking temperatures.

"Even in animals that tested positive in the brain, the prion has never been found in the muscle," said Terry L. Burkhardt, director of meat safety and inspection for the agency.

Concerns about chronic wasting disease may prompt more hunters to process their own deer this year, but Burkhardt believes the vast majority of deer will be processed by 350 meat processors licensed by the state.

Although compliance with the guidelines is voluntary, Burkhardt said: "I think they (processors) are very concerned and they will be very careful in the processing of deer to reduce any risk to a very low level."

The guidelines are available at Department of Natural Resources service centers and license outlets, and will also be distributed at deer registration stations.

The World Health Organization says there is no evidence that chronic wasting disease transmits to humans. Yet state and national health experts are investigating the deaths of three men who took part in wild game feasts in northern Wisconsin, which were first reported by the Journal Sentinel in July. The men, two from Wisconsin and one from Minnesota, died of rare brain diseases.

Areas to avoid

State officials are advising people not to eat any part of a deer that appears sick, and to avoid the eyes, brain, spinal cord, spleen, tonsils and lymph nodes of any deer.

According to Burkhardt, most, but not all, of these "high risk tissues" where the prions concentrate, are removed during normal field dressing and skinning.

Wearing latex gloves is a simple precaution.

"It (the prion) has never been found in the blood," Burkhardt said. "But there may be some contact with the spinal cord in the process. There shouldn't be, but there may be."

Care should be taken to avoid cutting through the spine in both field dressing and butchering.

When field dressing, don't be too concerned about locating the spleen -- a small red-purple organ located between the liver and stomach -- or several lymph nodes -- round tissue masses ranging from pea to quarter size -- located near the digestive system. They will be left with the gut pile.

However, butchers and home processors will have to be on the lookout for two specific lymph nodes, called popliteal lymph nodes. There is one in each hind leg, tucked deep between the muscles behind the knee joint.

"When you pull the muscles apart at the seam, the lymph node is exposed," Shelby Molina, a veterinarian with DATCP, explained.

Several other "superficial" lymph nodes are embedded in the deer's fat and should come off with the hide when you skin the deer, Molina said. If they stick to the muscle, cut them off and discard them.

Knives work best

When butchering, use a knife to cut meat away from the bone.

"You can further reduce risk by not cutting through any bones," Burkhardt said.

In general, Burkhardt said: "Just keep the boneless meat. Discard all fatty tissue, connective tissue, and glandular material. They are all significant by their appearance, which is different than meat."

If a deer was shot in the spine or any other high risk tissue area, Burkhardt said: "Liberally trim and remove all damaged tissue and surrounding tissue."

After all consumable meat has been processed, carefully remove the head and neck by cutting between the neck vertebrae using a knife designated for that purpose only. This will eliminate any contact with the brain, eyes, tonsils and additional lymph nodes.

"Using even a hand saw (to cut through the neck) would provide more risk than a knife," Burkhardt warned.

Clean knives and other equipment and disinfect them by soaking them for one hour in a 50/50 solution of household chlorine bleach and water.

Many hunters save their buck's antlers by sawing through the skull plate. "The recommendation is to use a hack saw blade only for that purpose and then dispose of it," Molina said.

The presence of chronic wasting disease in Wisconsin deer was first announced by the Department of Natural Resources in February. So far, 31 deer have tested positive for the disease, all in the Mount Horeb area.

For deer shot in the chronic wasting disease eradication zones, where infected deer have been found, or in the surrounding CWD management zone, meat from each deer should be kept separate. If your deer was tested for the disease, wait for the results before eating the meat.

At this point, Burkhardt said, carcass disposal remains an unresolved issue for the meat processing industry.

For individuals, the past practice was to simply put the bones in the garbage. This year, he said: "Because there have been a lot of concerns with this stuff going into landfills, they (hunters) may want to check with their local provider as to the suitability of that."

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