The Basics of Chronic Wasting Disease – Part 5
Pursue The Outdoors 06.21.11
To read part four of this article, click here.
Can Humans Become Infected With CWD?
Reports on the infectious nature of CWD in the media have been carefully worded to state that, “there is no evidence that CWD can be transmitted to humans.” However, this statement may be misleading, or misunderstood. A November 4, 2002, article on the Department of Health and Human Services’ website states, “Scientists do not know yet whether deer or elk with CWD might also transmit some form of TSE disease to people who eat or have close contact with them. With CWD beginning to spread over a wider geographical area in the United States, however, answering this question is of critical public health importance.”
An article on the United States Department of Agriculture’s website states, ” To date, there is no evidence that CWD has been transmitted or can be transmitted to humans under natural conditions. However, there is not yet strong evidence that such transmissions might occasionally cause diseases in humans, additional epidemiological and laboratory studies could be helpful. Such studies include molecular characterization and strain typing of the agents causing CWD in deer and elk and CJD in potentially exposed patients. Ongoing national surveillance for CJD and other neurological cases will remain important to assess the risk, if any, of CWD transmission to humans.” It may be several years before scientists are able to detect CWD in humans, because it is believed that it may take 10 or more years for CWD to manifest itself in humans.
Species Barriers
TSE diseases may not cause infections in animals of different species because of what scientists refer to as “species barriers.” Depending on how wide or strong this barrier is between different species, diseases like TSE’s may not cross the barrier between non-related species. In other words, it maybe difficult for a human to become infected with some new or existing form of TSE after they have eaten CWD infected meat. However, there is a hypothesis that the more times a TSE in transmitted through different animals of the same species, the stronger it becomes; and the stronger the TSE becomes, the more likely it is to cross the species barrier.
This may explain how the TSE known as scrapies in sheep resulted in the TSE known as Mad Cow Disease in cattle. Prior to the discovery of Mad Cow Disease in Great Britain, meat by-products of poultry, sheep and cattle were often used to feed livestock. If scrapies infected sheep by-products were fed to cattle, and the meat by- products from those cattle were fed to other cattle, the scrapies TSE may have become strong enough to cause Mad Cow Disease in the cattle. The Mad Cow Disease in the cattle may then have become strong enough to cause variant Creutzfeldt-Jakobs disease in humans who ate diseased beef.
This same sequence of events may have resulted in sheep scrapies causing CWD in mule deer or elk in the research facility in Colorado where CWD was first described. Since it is not likely that the mule deer in the research facility were fed scrapies infected meat by-products, it can be assumed that the mule deer were either infected after coming into close physical contact with infected sheep; or they may have eaten scrapies infected soil or licked some other surface (such as feed, feed bunks, fencing or buildings) which resulted in the infection of the deer. Because the species barrier between mule deer and elk is not very wide, diseased mule deer may then have infected elk. Or the elk may have been infected in some way by the sheep.
Although there is currently no evidence that CWD can be transmitted to humans, it was also previously believed that Mad Cow Disease could not be transmitted to humans. When talking about Mad Cow Disease in 1995, Steven Dorell, of the United Kingdom national media stated, “No conceivable risk.” John Major, then of the British Parliament, stated, “No conceivable risk, beef is safe … (in any meaningful sense of the word).” Despite these claims the human form of a TSE (referred to as variant Creutzfeldt-Jakob Disease) has been strongly linked to exposure of the TSE agent in Mad Cow Disease infected beef. Between October 1996 and November 2002, 129 cases of vCJD have been reported in the United Kingdom, six cases in France, and one case each in Ireland, Italy, Canada and the United States.
Chronic Wasting Disease is a serious concern for every outdoorsman, whether he be a hunter, conservationist or both. Keep up with updates on CWD and other hunting and conservation news at Outdoor Hub.
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