Deer can spread chronic wasting disease through saliva and blood, which means no part of an infected animal can be considered safe to eat, Colorado researchers discovered.
Up to now, there has been a widespread feeling that as long as the brain or lymph nodes were avoided, the rest of the deer was safe to eat.
The results of the study led by Colorado State University scientists will be reported in today's edition of Science.
Some herds in Colorado have no cases of CWD, and others have very low incidence. But among some herds around Fort Collins and Rocky Mountain National Park, the infection rate is as high as 6 percent.
And because deer with the disease, which causes them to stagger and lose weight, make themselves more frequent targets of hunters, chances can be quite good that the deer a hunter kills in an area with a high infection rate has CWD.
The first of Colorado's rifle seasons for deer and elk begins Oct. 14.
While there is no proof that humans can get CWD from eating the flesh of an infected deer, such cross-species transfer has been seen in a related prion-type illness - mad cow disease.
Ed Hoover, CSU microbiology professor and principal scientist for the study, suggests that hunters pay strict attention to the advice from the Colorado Division of Wildlife: Don't eat any part of a deer until its brain and lymph nodes have been tested for the presence of the abnormal prions that signal CWD.
Hunters also should wear gloves when they dress an animal to guard against accidental infection.
The finding that saliva can provide a pathway for the disease means CWD can spread easier than scientists previously thought, Hoover said.
Grooming and nibbling are common social behavior among deer. A diseased deer may chew on the hair of a noninfected deer. Later, when the healthy deer grooms itself, it can get infected through the saliva on the hair.
The CSU team used about a dozen deer that were kept indoors to ensure they couldn't get CWD from any source but the variables used in the study.
One group of deer were given the saliva of known infected deer to ingest. Parts of their tonsils were then clipped and tested for the presence of the abnormal prions that comprise CWD. Some had the disease in three months, others got it within a year.
A second group injected with the blood of infected deer also developed the disease. That means, according to researchers, that CWD can spread throughout a deer's body and throughout its flesh, albeit in smaller concentrations than in the brain and tonsils.
It also means that CWD possibly could be transferred through the bite of a mosquito.
Hoover's group already has embarked on a follow-up study.
In the hunt
Â• The first of Colorado's rifle seasons for deer and elk begins on Oct. 14.
scanlon@RockyMountainNews.com or 303-442-8729
Copyright 2006, Rocky Mountain News. All Rights Reserved.
Bad News for Venison Eaters--Mad Cow-Like Disease Among Deer is Highly Infectious
Study sounds CWD alarm
CSU scientists find disease can spread in deer saliva, blood
By Bill Scanlon
Rocky Mountain News, October 6, 2006
Straight to the Source