ARLINGTON, Virginia, May 13, 2004 (ENS): Transmission of chronic
wasting disease can take place not just through animal-to-animal
direct contact but also by exposure to environments
contaminated by whole carcasses or excrement of infected
animals, a team of researchers from Colorado and Wyoming
Colorado Division of Wildlife veterinarians Michael
Miller and Lisa Wolfe, Colorado State University scientist
Thomas Hobbs and University of Wyoming scientist Elizabeth
Williams made the discovery, and they expect it to change
the way wildlife managers handle their responses to
the disease, which is similar to mad cow disease.
Miller said, "We have long suspected that chronic
wasting disease could be transmitted when healthy deer
were exposed to excreta and carcasses of mule deer that
had the disease," said Miller. "Our findings
show that environmental sources of infection may contribute
to chronic wasting disease epidemics, and illustrate
how potentially complex these epidemics may be in natural
The research confined healthy deer in three sets of
separate paddocks. In the first set, healthy deer were
exposed to another deer already infected with chronic
wasting disease; in the second set, deer were exposed
to carcasses of deer that had died of chronic wasting
disease; in the third set, deer were confined in paddocks
where infected deer had previously been kept.
A few of the healthy deer contracted chronic wasting
disease under all three exposure scenarios over the
course of one year.
"We've had a great deal of circumstantial evidence
suggesting that indirect transmission occurs,"
said Williams. "The experimental findings show
that we need to consider several potential exposure
routes when attempting to control this disease."
"Ultimately, we want to develop models that predict
the behavior of the disease," Hobbs explained.
"For example, we would like to predict how prevalence
changes over time in different areas of Colorado."
Hobbs said previous disease models have been based
on animal-to-animal contact as the sole source of infection
and that disease prevalence was expected to decline
as the number of infected animals is reduced. But the
new finding that contaminated environments can transmit
the disease means that declines in infection rates may
be much slower than would be predicted by models that
only consider animal-to-animal transmission."
Most researchers believe the disease is caused by an
aberrant prion protein that misfolds in the brain, destroying
brain tissues as it progresses in the same process that
causes mad cow disease and its human form variant Creutzfeldt-Jakob
Symptoms include lethargy, excessive salivation, loss
of wariness of predators and slowly deteriorating body
condition. The disease is always fatal and there is
no known cure or treatment to prevent chronic wasting
Federal and state health officials have found no connection
between chronic wasting disease and human health. As
a precaution, officials recommend that the meat of animals
infected with chronic wasting disease should not be
Chronic wasting disease is a fatal neurological ailment
of elk, white-tailed deer and mule deer.
Miller said that while the research shows environmental
contamination is possible in a captive setting, the
impacts in the wild are still unknown.
"Diseases like chronic wasting disease are poorly
understood and of rising concern," said Sam Scheiner,
program director in NSF's division of environmental
biology, which funded the research. "This study
provides significant new information showing the potential
for transfer of the infection through the environment
after many months.
Originally posted at: http://www.ens-newswire.com/ens/may2004/2004-05-13-097.asp