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Chronic Wasting Disease (CWD) is a contagious neurological disease affecting deer, elk and moose. It causes a spongy degeneration of the brains of infected animals resulting in emaciation, abnormal behavior, loss of bodily functions and death.

CWD belongs to a group of diseases known as transmissible spongiform encephalopathies (TSEs). Within this family of diseases, there are several other variants that affect domestic animals. Scrapie has been identified in domestic sheep and goats for more than 200 years. Bovine is a spongiform encephalopathy (BSE) in cattle (also known as "mad cow disease"), and transmissible mink encephalopathy in farmed mink.
Clinical Features:

Adults: 17 months to >15 years
Most 3-5 years
Sex: males, females
No strict seasonality
Clinical duration: days to >1year, usually months
Incubation period: min: ~17 months, max: unknown

Diagnosis
Clinical signs of CWD alone are not definitive diagnosis based on an examination of the brain for spongiform lesions and/or accumulation of the CWD. This test is based on use of monoclonal antibodies and chromogens to detect accumulation. The parasympathetic vagal nucleus in the dorsal portion of the medulla oblongata at the obex is the most important site to examine for diagnosis of CWD because of its early involvement following infection. The segment of the medulla oblongata required for testing can be easily and swiftly removed from the brain through the foramen magnum and the specimen appropriately preserved. The obex still in 10% of when alive and the rest of the brain must be frozen.

It is important to test the lymph nodes which commonly require the tester to cut the head and neck off the deer for accurate testing of CWD.

It is critically important that the correct portion of the brain be sampled for a meaningful test. The parasympathetic vagal nucleus in the dorsal portion of the medulla oblongata at the obex is the most important site to examine.
Photo Courtesy of Wyoming Game and Fish Department