|
North
Carolina Proactive Against Deer Disease
 Raleigh,
N.C. (May 16) - In response to a national wildlife disease situation,
the N.C. Wildlife Resources Commission yesterday adopted an emergency
rule to keep North Carolina's deer herd healthy. The target of the emergency
rule, Chronic Wasting Disease (CWD), came to national attention on September
21, 2001, when the U.S. Secretary of Agriculture issued a "declaration
of emergency" concerning CWD in captive elk.
Chronic Wasting Disease
(CWD) is a transmissible spongiform encephalopathy (TSE) of deer and elk.
A progressive disease, CWD typically induces chronic weight loss leading
to death. The majority of infected animals also experience behavioral
changes, including decreased interactions with other animals, listlessness,
lowering of the head, blank facial expression and repetitive walking in
set patterns. Most deer show increased drinking and urination and
may have excessive salivation and grinding of the teeth.
Wildlife professionals
have identified CWD in wild herds of deer and/or elk in Wyoming, Nebraska,
Colorado, South Dakota, Wisconsin and Saskatchewan. The disease also occurs
in captive herds in South Dakota, Nebraska, Colorado, Oklahoma, Montana
and Kansas and two Canadian provinces. Although the disease has not appeared
in any deer or elk in North Carolina, recently private individuals have
imported deer from infected states. Therefore, to protect native wildlife
and keep North Carolina CWD-free, the Commission is banning all importation
of live animals from the family Cervidae (which includes deer and elk)
into the state and transportation of these animals within the state, effective
May 17, 2002.
Although transmitted
between animals, the pathway of disease transmission from one animal to
the next is unknown. The CWD incubation period can last up to five years
(possibly longer) which compounds the problem of diagnoses. Currently,
the only way wildlife professionals have to diagnose CWD is through post-mortem
examination.
Citizens who currently
hold cervids legally in captivity can continue to do so, but must abide
by the transport and import restrictions. The Commission will consider
in July if further restrictions on captive herds are necessary. There
are no proposed changes to deer hunting regulations.
TSEs are neurological
diseases characterized by empty spaces in the brain matter, creating a
"spongy" appearance. Other known TSEs are: scrapie in sheep,
bovine spongiform encephalopathy in cattle, Creutzfeldt-Jakob Disease
and New Variant Creutzfeldt-Jakob Disease in humans. However, epidemiologists
with the Federal Centers for Disease Control and Prevention in Atlanta
and at the Colorado Department of Public Health and Environment studying
CWD found no link between it and any neurological disease that affects
humans. Finally, researchers—using controlled experiments with penned
animals—have documented no natural transmission of CWD from deer
or elk to livestock.
| Chronic
Wasting Disease Factsheet |
The Disease
Chronic wasting
disease (CWD) is a transmissible spongiform encephalopathy (TSE)
of deer and elk. TSEs are neurological diseases characterized
by microscopic empty spaces in the brain matter, creating a "spongy"
appearance. First recognized as a clinical "wasting" syndrome in
1967 in mule deer in a wildlife research facility in northern Colorado,
CWD was identified as a TSE in 1978. Other TSEs are:
scrapie in sheep, bovine spongiform encephalopathy in cattle, Creutzfeldt-Jakob
Disease and New Variant Creutzfeldt-Jakob Disease in humans.
However, there is no known relationship between CWD and any other
TSEs of animals or people.
To date, CWD
has been found only in cervids (members of the deer family) in North
America. Most cases of CWD occur in adult animals. CWD
is a progressive disease typified by chronic weight loss leading
to death. Behavioral changes also occur in the majority of
cases, including decreased interactions with other animals, listlessness,
lowering of the head, blank facial expression, and repetitive walking
in set patterns. Excessive salivation and grinding of the
teeth also are observed. Most deer show increased drinking
and urination.
CWD Locations
CWD has been
diagnosed in captive elk herds since 1978 in several states and
in two Canadian provinces. The locations of captive elk herds
with known CWD infection are: South Dakota, Nebraska, Colorado,
Oklahoma, Montana, Kansas, Alberta and Saskatchewan. Transportation
of elk from these herds is prohibited.
In the mid-1980s,
CWD was detected in free-ranging deer and elk in contiguous portions
of northeastern Colorado and southeastern Wyoming. In 2001,
CWD was also found in free-ranging deer in the southwestern corner
of Nebraska (adjacent to Colorado and Wyoming) and on February 2002
in Wisconsin. The areas of northern Colorado, southern Wyoming,
and southwestern Nebraska and southeastern Wisconsin in which free-ranging
deer and/or elk positive for CWD have been found are referred to
as the endemic areas. The is no transportation of cervids from infected
captive heards and wild cervids have not been translocated from
the endemic areas, either.
Species prone
to CWD include Rocky Mountain elk, mule deer, white-tailed deer,
and black-tailed deer. Researchers have placed CWD infected
deer and elk in close contact with wild ruminants and domestic cattle,
sheep, and goats to test for disease transmission. So far there
has been no evidence of disease transmission. Research is
ongoing to further explore the possibility of transmission of CWD
to other species.
The source
of infection
The agent
responsible for CWD (and other animal TSEs) has not been completely
characterized. The theory with the most supporting evidence
is that the CWD agent of infection is a prion. A prion is an abnormal
form of a normal protein, known as cellular prion protein, most
commonly found in the central nervous system. The abnormal
prion protein "infects" the host animal by promoting conversion
of normal cellular prion protein to the abnormal form. The
CWD agent is smaller than most viral particles and does not evoke
any detectable immune response in the host animal. Based on
experience with other TSE agents, the CWD agent is assumed to be
resistant to enzymes and chemicals that normally break down proteins,
as well as resistant to heat and normal disinfection procedures.
Stanley Prusiner,
a neurologist at the University of California's School of Medicine
won the Nobel Prize for Medicine in 1997 for his more than twenty
years of work investigating the pathogens responsible for TSEs.
He deduced that proteins that lack DNA called "protease resistant
prions" are the agents that transform other normal prions into their
own image, though scientists aren't sure if or how protease resistant
prions are naturally transmitted in a particular species.
Diagnosis
Researchers
are developing live-animal diagnostic tests for CWD. Until
such time as a live test is available, definitive diagnosis is based
on postmortem examination (necropsy) and testing. Scientists use
a technique called immunohistochemistry to test brain tissue for
the presence of the abnormal prion protein to diagnose CWD. Currently,
only the immunohistochemistry test can confirm CWD. Aspiration pneumonia,
which may be the actual cause of death, also is a common finding
in animals affected with CWD. On microscopic examination,
lesions of CWD in the central nervous system resemble those of other
TSEs.
Information
provided by:
USDA
Animal and Plant Health Inspection Service
Colorado Division of Wildlife
More Information
USDA—Animal
and Plant Health Inspection Service
USDA
and Dept of Interior Working Together
Wisconsin
Department of Natural Resources
Colorado
Division of Wildlife
University
of Wyoming Veterinary Laboratory
|
|
