Early tests of high-risk Ohio deer show no traces of chronic wasting disease. Labs soon to perform more extensive tests
REYNOLDSBURG – Everything will change for Dr. Sheila D. Grimes if she finds a pink-stained sample of tissue from a deer’s brain on her microscope slide.
That will signal the arrival of chronic wasting disease in Ohio’s white-tailed deer herd. It will have a major impact on hunting and might indicate a threat to human health.
“It would mean a lot more work, a lot more testing… and a lot more concern,” said Grimes, a veterinary pathologist who is spearheading the Ohio Department of Agriculture’s deer-testing program.
Chronic wasting disease, or CWD, is one of a family of fatal neurological disorders called transmissible spongiform encephalopathies. Best known of these disorders is mad cow disease, which has spread to cows in Europe and Asia, and variant Creutzfeldt-Jakob disease, which kills people who consume beef from animals infected with mad cow.
Disease moves east
The deer disease has been found in Western states for decades and is gradually moving east.
Ohio’s Animal Disease Diagnostic Laboratory — an unobtrusive one-story brick building outside Columbus — is one of 15 federally approved centers testing for chronic wasting disease around the country.
Grimes and her team of seven scientists recently completed CWD testing on 1,101 deer from Indiana under a contract with the federal government. They now are getting started on 650 deer shot in December by Ohio hunters.
Testing for CWD is “very time-consuming and very labor intensive,” Grimes said, explaining that it requires care and skill in tracking and record-keeping as well as analysis by a trained pathologist.
Since beginning the testing in December, the Ohio lab has not detected CWD.
Testing is being coordinated by the Ohio Department of Agriculture, the Ohio Department of Health, the Ohio Department of Natural Resources and the U.S. Department of Agriculture.
Deer also checked for TB
Ohio’s deer are being checked for both CWD and bovine tuberculosis, which has been found in Michigan’s herd. Ohio previously tested for TB in deer in 1996, 1998 and 2000 with negative results.
The state lab can process about 100 to 150 deer per week, with a CWD test costing $15 per animal and the tuberculosis test, $5.50.
Sections of the brain are analyzed for chronic wasting disease; the lymph nodes are tested for bovine tuberculosis.
The CWD tests use immunohistochemical staining, the most-accepted means of detection and the standard test ordered by the USDA. The test is antibody-based.
Like all transmissible spongiform encephalopathies, CWD is marked by the presence of abnormally shaped proteins, called prions, in the brain. Antibodies bind to abnormal prions in the deer tissue. The test allows a colored agent to be bound to the material.
The Ohio deer being tested were killed by hunters in the southeast part of the state, near Toledo and in Wayne, Holmes, Geauga and Ashtabula counties, where there are large numbers of deer farms. Such farms have been blamed by some people for the spread of chronic wasting disease around the country.
Of the 650 Ohio deer being tested, about 30 were taken by hunters to the state lab for CWD analysis. The rest were killed by hunters and selected by the Ohio Division of Wildlife.
The state’s CWD testing of Ohio deer is expected to be completed in late February or early March. Tuberculosis testing will take longer to complete.
No sign of disease here
The lab already has tested a few high-risk Ohio deer for CWD and has found no evidence of the disease in these animals that had been losing weight in the wild and were brought in by the state.
Grimes said the actual finding is “not detected.” The lab does not say the results are negative, because CWD has a long incubation period.
Results from the lab in Reynoldsburg are being forwarded to the USDA’s National Veterinary Services Laboratory in Ames, Iowa,which will make any official announcements about CWD.
The disorder was first reported in 1967 in captive deer in Colorado and until the 1990s was restricted to animals along the Colorado-Wyoming line.
Then it turned up in Nebraska, South Dakota, Montana, New Mexico, Oklahoma and Kansas, and the Canadian provinces of Alberta and Saskatchewan. It was confirmed in Wisconsin’s wild deer herd last year, on a Minnesota elk farm last summer and in Illinois last November.
Transmission a mystery
Experts don’t know how CWD is transmitted from animal to animal.
The disease attacks and alters the brain. Symptoms include excessive salivation, trouble swallowing, difficulty judging distance, a lack of coordination and drooping ears. It’s always fatal.
Though there are no confirmed cases of chronic wasting disease infecting a person, there is anecdotal evidence of a few hunters who ate deer or elk later dying of rare neurological disorders.
In Wisconsin, where 32 deer have been confirmed with CWD, state officials expect to test 200,000 deer this year, and efforts are under way to kill 25,000 deer to wipe out the wild herd in an infected area west of Madison.
Ohio soon could be testing up to 20,000 deer a year for the federal government, although the state first needs new equipment to automate the testing process, said Dr. Beverly Byrum, director of the lab.
Already, the lab has been bolstered by the addition of six CWD testing modules with $180,000 in new high-tech equipment from the USDA.
To test for CWD, a deer’s head is removed in the field, placed on ice and sent to the lab within 48 hours. A portion of the brain — the obex — is removed, along with lymph nodes.
Grimes said a test of the brain samples takes seven to 10 days.
Studies have shown that the abnormal prion protein that triggers CWD is first detected in the obex portion of the brain stem. As the disease spreads, the prions can be later found in other parts of the animal.
The obex is not big — perhaps 2 to 3 centimeters in length. The three pairs of deer lymph nodes are also small, about 2 centimeters in diameter.
Getting to the deer’s brain stem and to the lymph nodes begins at what looks like a kitchen sink where lab workers, armed with power tools and wearing protective gear, cut their way into the carcasses.
The deer heads then are shipped to an out-of-state incinerator for disposal.
Ohio lab one of first
The Ohio facility was one of the first six labs around the country to be made part of the growing national CWD testing.
That resulted from its proficiency in testing for scrapie — a transmissible spongiform encephalopathy that attacks sheep and goats — under a 2001 federal program, Byrum said.
In 2001-02, Ohio had more confirmed scrapie cases (38) and more infected flocks (13) than any other state.