Live testing created for deer Move may help stop spread of chronic wasting

December 10, 2001 The Denver Post by Theo Stein
Colorado researchers have developed the first live test for chronic wasting disease, a breakthrough that is expected to help them control the spread of the fatal brain-eating malady in wild deer herds.

While the new tonsil test will never replace hunter-harvest surveys, it does give researchers a way to evaluate deer herds that can't be hunted, such as those in suburban settings or in Rocky Mountain National Park.

And it will also help researchers determine how land-use patterns affect the spread of CWD in northeast Colorado and adjacent parts of Wyoming. Some researchers suspect residential areas may act as deer refuges, unnaturally concentrating the animals and increasing the spread of the disease. 'It's a gigantic step,' said Terry Messmer, a University of Utah professor who studies wildlife conflicts of the new test. 'Anything that will help us develop long-term control measures is significant.'

The new test works because the mutant proteins that cause the disease concentrate in deer tonsils and other lymph system tissue during its early stages. Biologists must first tranquilize the animals before snipping off a piece of tonsil with a biopsy tool. The animal is then tagged for later identification and released.

But obtaining tonsil samples from live deer is several times more expensive than testing hunter-killed animals.

And the test doesn't work on elk, so it won't prevent the slaughter of 1,500 elk exposed to a current outbreak of CWD on Colorado ranches.

'It's like getting a nifty new screwdriver for your tool kit,' said Mike Miller, a Colorado Division of Wildlife veterinarian and a principal investigator in the study. 'It will come in handy from time to time, but if you're pounding nails, it's not going to replace a hammer.'

The new test was developed jointly by the wildlife agency and the CSU Natural Resource Ecology Lab with the aid of a $ 2.1 million National Science Foundation grant.

Miller said the procedure is evolutionary rather than revolutionary, as it builds on overseas research on a live test for scrapie, a related neurological disorder in sheep.

The DOW has been using tonsils instead of brain samples to diagnose CWD in deer heads turned in by hunters for two years. DOW began evaluating deer tonsils as a potential indicator in 1996.

Tom Hobbs, senior scientist with the Colorado State University Natural Resource Lab, said the procedure conclusively demonstrated its worth during this summer's field trial, when crews took tonsil samples from 160 deer near Livermore and Estes Park.

'We had very good agreement with hunter-harvest data,' Hobbs said.

About five percent of the 117 deer darted in Estes Park had the disease. Sixteen percent of the 44 deer sampled near Livermore were CWD positive.

With results in hand, the DOW now intends to go relocate sick animals identified by the test to remove them and others that might be incubating the disease. Heavily-infected herds revealed by future testing will also be targeted for culling.

'When you look at the potential economic impact across the West, mule deer are basically the bread and butter for wildlife agencies,' said Messmer, who is also a director with the Mule Deer Foundation. 'If it jumps to wild populations outside northeast Colorado and starts to spread, it could be catastrophic not only for mule deer but for state agencies.' Anything that can be done to prevent the spread of the disease is critical, he said.

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