AR-News: (US)CHRONIC WASTING DISEASE UPDATE 2004 (02)

[Ronda Roaring]

Civitas <civitas at linkny.com> wrote:Date: Wed, 19 May 2004 02:53:11 -0400 (EDT)
From: ProMED-mail 

Subject: PRO/AH> Chronic wasting disease update 2004 (02)

CHRONIC WASTING DISEASE UPDATE 2004 (02)
****************************************
A ProMED-mail post

ProMED-mail a program of the
International Society for Infectious Diseases


Date: 18 May 2004
From: Rochelle S Spicer-Monroe 
Source: National Science Foundation, 12 May 2004 [edited]


New research supports theory that indirect transmission of CWD is possible
in mule deer
- --------------------------------------------------------------
A team of researchers has reported that chronic wasting disease (CWD) can
be transmitted through environments contaminated by whole carcasses or
excrement of animals infected with the pathogen that causes CWD. The
research confirms long-held theories that CWD can be indirectly spread
through environmental sources, in addition to direct interactions between
infected and healthy mule deer.

Funded by the National Science Foundation (NSF) and the National Institutes
of Health, the study results were published online last week in the journal
Emerging Infectious Diseases
. The authors are
Colorado Division of Wildlife (DOW) veterinarians Michael Miller and Lisa
Wolfe, Colorado State University (CSU) scientist Thomas Hobbs and
University of Wyoming scientist Elizabeth Williams.

"Diseases like CWD 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. The knowledge will substantially alter how we manage the
disease in wild and domestic animals."

Based on anecdotal observations, "we have long suspected that CWD 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 CWD epidemics, and
illustrate how potentially complex these epidemics may be in natural
populations."

Added Williams, "We've had a great deal of circumstantial evidence
suggesting that indirect transmission occurs. The experimental findings
show that we need to consider several potential exposure routes when
attempting to control this disease."

Hobbs said the research could be important in helping to slow the spread of
CWD. "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 was reduced. "Our findings that
contaminated environments can cause transmission means that these declines
in infection rates may be much slower than would be predicted by models
that only consider animal-to-animal transmission." Miller said that while
the research shows environmental contamination is possible in a captive
setting, the impacts in the wild are still unknown.

The research confined healthy deer in 3 sets of separate paddocks. In the
1st set, healthy deer were exposed to another deer already infected with
CWD; in the 2nd set, deer were exposed to carcasses of deer that had died
of CWD; in the 3rd set, deer were confined in paddocks where infected deer
had previously been kept. A few of the healthy deer contracted CWD under
all 3 exposure scenarios over the course of one year.

Chronic wasting disease is a fatal neurological ailment of elk,
white-tailed deer and mule deer. Most researchers believe the disease is
caused by an aberrant prion protein that misfolds in the brain, destroying
brain tissues as it progresses. Clinical signs 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 CWD.

Federal and state health officials have found no connection between CWD and
human health. As a precaution, officials recommend that the meat of animals
infected with CWD should not be eaten.

"Although live deer and elk still seem the most likely way for CWD to
spread geographically, our data show that environmental sources could
contribute to maintaining and prolonging local epidemics, even when all
infected animals are eliminated," Miller said. He said the appropriateness
of various culling strategies may depend on how quickly the CWD agent is
added to or lost from the environment.

[media contact: Cheryl Dybas 703/292-7734]

- -- 
ProMED-mail



[Then one has to wonder whether this is an infectious disease, and is the
prion an infectious agent? This is perhaps a rhetorical question and may
not yet have a justifiable answer. &shy; Mod.TG]

[see also:
Chronic wasting disease update 2004 (01) 20040408.0959]

.............tg/pg/sh


		
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