The Basics of Chronic Wasting Disease – Part 1

Chronic Wasting Disease is an ailment affecting all cervids (members of the deer family of species). This primer on the disease will educate you on this serious affliction.

What Is Chronic Wasting Disease?

By now most of my readers know that I do a lot of research and that the findings of my research are a large part of what I write about. A lot of my research is done in the field, observing animals and recording their actions. But I also do background research to find out what others have discovered about whatever subject I intend to write about.

Lately I have spend a lot of time on the Internet looking for all the information I could find on Chronic Wasting Disease (CWD), Transmissible Spongiform Encephalopathies (TSE’s), prions (PrP, pronounced PREE-ons), and variant Creutzfeldt-Jakob Disease (vCJD). I’ve looked at several articles, documents and research findings on the World Health Organization (WHO) website, the United States Department of Agriculture (USDA) website and their Animal and Plant Health Inspection Services (APHIS) website, the Health and Humans Services (HHS) website, the Center for Disease Control (CDC) website, the National Institute of Health (NIH) website, the United States Geological Survey (USGS) website, the Chronic Wasting Disease Alliance website, NOVA’s website, the Nature website and several research institute and university websites.

As a result of all my background research on CWD I’ve got a file folder about an inch thick filled with information on CWD and other TSE’s. Although there is a lot of information about CWD the web, much of it is about hypotheses, theories, scientific findings, and future research into the possible cause of CWD. But, what I wanted to find out during my research was “What are TSE’s? What is a prion? And how is CWD spread?” And more importantly, “How infectious is CWD to deer and elk, and can humans become infected with CWD?”

What Are TSE’s?

TSE’s are a group of fatal, degenerative, neurological disease of animals and humans. The animal forms of TSE’s include scrapies in sheep, which has been known for several hundred years; Transmissible Mink Encephalopathy (TME) in mink; Feline Spongiform Encephalopathy (FSE) in cats, Bovine Spongiform Encephalopathy (BSE) or Mad Cow Disease in cattle; and Chronic Wasting Disease (CWD) in white-tailed deer, mule deer, black-tailed deer, and elk in North America. Mice and hamsters have also been infected with TSE’s in laboratory research.

The human forms of TSE’s include Kuru disease found in the Fore tribe of Papua, New Guinea with infection occurring from contact with diseased individuals, or after consuming the brain tissue of diseased individuals; Gerstmann-Straussler-Schenker syndrome (GSS) which occurs in persons with an apparent hereditary predisposition; Fatal Familial Insomnia (FFI) which occurs in families, and appears sporadically; Creutzfeldt-Jakob Disease (CJD) which appears sporadically in about 1 in 1 million people, which has also caused infections in individuals who have received transplants or other products from previously diseased individuals, or who have come in contact with contaminated surgical instruments; and variant Creutzfeldt-Jakobs Disease (vCJD) which is believed to be have caused infections in humans who have eaten Mad Cow Disease infected beef.

Most scientists accept the theory that TSE’s are caused by little-understood abnormal protein called a prion (PrP), which is a form of protein found in the cells of the nervous system and other body tissues. However, some scientists question whether or not prions are the infective agent of TSE’s. There are also theories that TSE’s may be caused by bacteria known as Spiroplasma or by a virus or virino. There is also a hypothesis that TSE’s may occur as the result of a nutritional copper deficiency. Many scientists in the wildlife community dismiss these alternative ideas, and most of the research into the cause of CWD is in the area of prions.

Prions

Nobel Prize winning neurologist Dr. Stanley Pruisner first described an abnormal form of a prion that was resistant to enzymes that break down normal proteins. These abnormal, protease resistant prions have the ability to transform normal prions into an abnormal state. These abnormal prions accumulate in the in the brain, lymph nodes and tonsils. This accumulation of prions in the brain of infected animals and humans produces sponge-like holes in the brain, and eventually results in death.

Variant Creutzfeldt-Jakobs Disease

Variant CJD is similar to Creutzfeldt-Jakobs Disease (CJD) in that it is found in humans. But, it varies from CJD in that it looks different under a microscope. And instead of just spontaneously occurring (like cancer does) it is believed to be infectious, occurring in humans who have eaten beef from Mad Cow Disease infected cattle. Variant CJD has occurred in people as young as 29 years old, whereas CJD rarely occurs in people under 65. Variant CJD also appears to have a longer duration of illness; 14 months as opposed to 4.5 months for CJD, and it may have as long as a 10 year incubation period. As of November 2002, 139 cases of vCJD in humans have been linked to Mad Cow Disease infected beef.

To continue to part two of this article, click here.

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