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teamasc
Forum Admin
1348 Posts |
 Posted - 09/13/2009 : 19:49:30
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September 10, 2009
Study Spells Out Spread of Brain Illness in Animals
By SANDRA BLAKESLEE
Researchers are reporting that they have solved a longstanding mystery
about the rapid spread of a fatal brain infection in deer, elk and moose
in the Midwest and West.
The infectious agent, which leads to chronic wasting disease, is spread
in the feces of infected animals long before they become ill, according
to a study published online Wednesday by the journal Nature. The agent
is retained in the soil, where it, along with plants, is eaten by other
animals, which then become infected.
The finding explains the extremely high rates of transmission among
deer, said the study’s lead author, Dr. Stanley B. Prusiner, director
of the Institute for Neurodegenerative Diseases at the University of
California, San Francisco.
First identified in deer in Colorado in 1967, the disease is now found
throughout 14 states and 2 Canadian provinces. It leads to emaciation,
staggering and death.
Unlike other animals, Dr. Prusiner said, deer give off the infectious
agent, a form of protein called a prion, from lymph tissue in their
intestinal linings up to a year before they develop the disease. By
contrast, cattle that develop a related disease, mad cow, do not easily
shed prions into the environment but accumulate them in their brains and
spinal tissues.
There is no evidence to date that humans who hunt, kill and eat deer
have developed chronic wasting disease. Nor does the prion that causes
it pass naturally to other animal species in the wild.
Besides mad cow and chronic wasting disease, the prion diseases include
Creutzfeldt-Jakob, which leads to dementia and death in humans. Each of
these diseases is caused by a different strain, and all strains behave
somewhat differently.
In the case of chronic wasting disease, “it turns out prions exploit
the oldest trick in the book used by pathogens and parasites,” said
Mike Miller, a veterinarian at the Colorado Division of Wildlife who is
an expert on chronic wasting disease.
“Fecal-oral transmission is very effective,” Dr. Miller continued.
Each deer excretes about two pounds of fecal pellets a day. As wild
herds move around, or captive herds are trucked between states, more
soil becomes infected.
In captive herds, up to 90 percent of animals develop the disease, Dr.
Prusiner said. In wild herds, a third of animals can be infected.
“This is an important finding,” said Judd M. Aiken, a leading prion
expert who is director of the Alberta Veterinary Research Institute in
Canada and who was not involved in the new study. “Most of us
suspected that prions might be spread in feces, but we needed proof.”
“The fact that prions are shed at a preclinical stage of the disease
is very significant,” Dr. Aiken added.
The study was carried out in two parts. First, Dr. Miller and his team
infected five mule deer by feeding them brain tissue from an infected
animal. They took fecal samples before infection and at three to six
months afterward. The deer came down with chronic wasting disease 16 to
20 months later.
Four to nine months after infection, the deer began shedding prions in
low levels in their feces, even though they had no symptoms.
Surprisingly, an infected deer could shed as many prions at this stage
as would accumulate in its brain during terminal disease.
In the second part of the experiment, Erdem Tamguney, an assistant
professor at Dr. Prusiner’s institute, created a strain of mice with
deerlike prions in their brains.
When Dr. Tamguney inoculated the brains of these mice with feces from
infected but asymptomatic deer, half developed symptoms of chronic
wasting disease. Fourteen out of 15 fecal samples transmitted the
disease to some of the mice.
Dr. Aiken said prions tended to bind to clay in soil and to persist
indefinitely. When deer graze on infected dirt, prions that are tightly
bound to clay will persist for long periods in their intestinal regions.
So there is no chance chronic wasting disease will be eradicated, he
said. Outside the laboratory, nothing can inactivate prions bound to
soil. They are also impervious to radiation.
Todd Alexander
ASC Membership Services Manager
talexander@team-asc.com
www.team-asc.com
734-552-4839
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brianjordan
Junior Member
161 Posts |
Posted - 09/14/2009 : 08:44:11
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That is most certainly bad news. Does this mean we shouldn't even be eating venison? More and more people are coming down with Dementia and other brain-related illnesses.
Brian Jordan
810-348-1667
jegorah@yahoo.com
michigan sportsman handle: brian
*** Taking care of land is everyone's responsiblity. Please do your part to clean up litter when you see it while out scouting or hunting. *** |
Edited by - brianjordan on 09/14/2009 08:46:55 |
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teamasc
Forum Admin
1348 Posts |
Posted - 09/14/2009 : 15:58:33
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As long as you aren't eating the raisinettes in the woods, this wouldn't effect you, since the study shows the prions aren't in the meat, only the intestines at the time of this high infection period. Also, they aren't entirely sure that it can transmit to humans at this point.
Todd Alexander
ASC Membership Services Manager
talexander@team-asc.com
www.team-asc.com
734-552-4839 |
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Not good news regarding CWD.
