Chronic Wasting Disease
(This 742nd Buffalo Sunday News column was first published on June 19, 2005.)
It seems that every time we turn around we find another threatening disease.
Botulism is killing thousands of ducks and other water birds in Lakes Erie and Ontario. The nectria fungus is attacking many of our beautiful beech trees and the pathogen is also threatening our native oaks. (When I asked the former Buffalo forester, Ed Drabek, about this problem a few years ago, he told me that every tree has its insect invaders and its diseases.) Our jays and crows are only now rebounding from their bout with West Nile virus. So are some of us; a few human deaths were even recorded. Several years ago mad cow disease -- a.k.a. bovine spongiform encephalopathy, BSE -- forced the culling of thousands of cattle from herds in this and other countries after the disease was communicated to a few humans. New BSE cases have recently been identified in western United States and Canadian cattle.
Now we have a threat called chronic wasting disease (CWD), an illness of deer and elk that was until recently restricted to a tri-corner area of Colorado, Wyoming and Nebraska. Unfortunately, five white-tailed deer from two captive herds in Oneida County east of Syracuse have tested positive for this disease and in late April a wild deer from Oneida County east of Syracuse was confirmed to have the disease.
Like BSE, CWD attacks the brain. As in mad cow disease a rogue protein, a prion, invades healthy brain tissue, riddling it with holes. Symptoms of the unfortunate deer with this affliction include weight loss, drooling and difficulty swallowing, excessive thirst and urination, followed by loss of muscle coordination and head tremors. Their loss of weight -- wasting away -- is what gives the disease its name. Death occurs within months of the onset and there is no known cure.
Although the mode of transmission is not fully understood, it appears to be direct animal-to-animal contact or indirect exposure to contaminated food or water.
In the west where hunting is central to their economy, what has been called "a wildlife slaughter of historic scale" is underway. Biologists are hunting wild deer to test for CWD. Meanwhile hunting seasons and bag limits have been increased in hopes of stopping its spread.
The early response to CWD in New York has been thorough but less dramatic. Our state Department of Agriculture and Markets is testing and destroying deer in the herds in which the deer testing positive were found. Associated herds have been quarantined and possible links with the two infected herds investigated. Meanwhile, the Department of Environmental Conservation (DEC) is conducting intensive monitoring of the wild deer population surrounding the index herd to ensure that CWD is not spreading further among it as well. DEC is also limiting transportation and importation of deer and elk carcasses.
Normally CWD is restricted to animals of the deer family, just as BSE is to cattle. The fear is that the disease will mutate and jump species to humans as did mad cow disease. A related worry is that CWD would jump in another direction -- to cattle.
Several human deaths from prion disease in the west have suggested possible links to CWD but a study by the Centers for Disease Control tells us that "the risk, if any, of transmission of CWD to humans is low." In contrast, however, one lab experiment demonstrated that the disease could be undetectable in one group of exposed mice, then, when passed on to another group, strike with uniform deadliness. Further research is, of course, ongoing.
What should be the response to CWD? The same study suggests that hunters should "wear gloves when field-dressing carcasses...and minimize handling of brain and spinal cord tissues." Meanwhile we should all avoid eating deer meat obtained from areas where CWD has been identified. Still more important, parents should counsel children not to touch dead deer found in the wild.
I salute our federal and state agencies for taking this new threat seriously and acting promptly. Even those who have problems with the excess deer of our suburbs would not want to see this handsome species attacked by this deadly disease.-- Gerry Rising