|
Chronic
wasting disease (CWD) is an infectious neurological disease of cervids,
which include North American deer and elk. CWD is a transmissible
spongiform encephalopathy (TSE), caused by an abnormal protein or "prion."
This is similar to the disease agent that causes scrapie in sheep and BSE
in cattle.
From the
time the disease was first recognized as a clinical entity in 1967 it has
mostly been limited to the geographic region of the western states and
western Canada. More recently, it has spread into some mid-west states,
then as far east as New York (diagnosed in March 2005) and most recently
found in free roaming deer in West Virginia. The disease has not been
diagnosed in any countries other than the United States and Canada, and
there is no evidence of any relationship between CWD and other prion
diseases in animals or man.
CWD was
first reported in captive mule deer in the mid 1960s from a wildlife
facility in Colorado. The exact origin of the disease cannot be
established because, like many diseases, it may have existed for a while
before it was recognized as a separate disease. That fact, along with the
long incubation of prion diseases, makes it very difficult to pinpoint the
cause of the original cases of the disease. CWD is a disease of adult
deer, with the youngest documented case being in an 18-month-old deer.
Most cases fit into the three- to four-year-old range, and have
occasionally been seen in the eight- to nine-year-old range.
Chronic
wasting disease is named for its most consistent characteristic—chronic
weight loss accompanied by dehydration. The disease causes progressive
degeneration of the central nervous system. Other clinical signs include
changes in temperament (loss of fear of humans, nervousness,
hyperexcitability), changes in behavior (teeth grinding, walking in
repetitive patterns), incoordination, excessive thirst and urination,
drooping of the head and ears, and excessive salivation. The incubation
period (the time between becoming infected and showing signs of illness)
is usually 18 to 24 months, but can range up to 36 months. The health of
the animal usually deteriorates over a period of 12 months. There is no
treatment for CWD and the infection is 100 percent fatal.
While the
exact method of transmission is unknown, most experts think that CWD is
most likely spread among cervids (deer) through contact with bodily fluids
such as blood, saliva, urine and feces. Evidence exists that the disease
may be transmitted from mother to offspring. The disease may be
transmitted simply through a contaminated environment. Feeding areas tend
to concentrate deer and may facilitate animal-to-animal transmission. For
that particular reason, the disease prevalence in positive captive herds
may approach 90 percent. And because of the concentration of animals and
the environmental factors, it is very difficult to eradicate from a
captive herd once the disease enters the herd.
Again, it
is worth emphasizing that CWD has no proven human health risk. Because BSE
is also a TSE, questions have been raised about the public health
implications of CWD. A thorough investigation was done by the Center for
Disease Control (CDC) and Prevention after two cases of classical
Cruetzfeldt-Jacobs Disease (CJD), a human TSE was diagnosed in two men who
were avid deer hunters. All related factors of these cases have been
thoroughly investigated by the CDC and the official declaration from the
center is that while caution in the hunting and processing of deer in CWD
endemic areas is recommended, there is no known risk to the human
population.
The State
of Alabama Department of Agriculture and Industries, in cooperation with
the USDA Veterinary Services and the Alabama Department of Conservation
and Natural Resources have developed a CWD Surveillance Program through
our state veterinary diagnostic laboratory system. Over the last three
years more than 2,000 deer were sampled as a part of the surveillance
program and all have tested negative for CWD. The surveillance program is
already underway this year as well. There have been no CWD positive deer
diagnosed in Alabama or neighboring states, and Alabama conservation laws
restricting the importing of deer into the state serves as a firewall to
keep the disease out.
It is
strongly suggested that meat from deer that appear sick not be consumed.
There are a number of diseases that could cause deer to be ill, some of
which could affect humans. It is also recommended that the meat should be
deboned using rubber gloves and be free of brain tissue, spinal cord or
lymph nodes. If a hunter or landowner should see or harvest a deer that
appears sick please contact the Alabama Department of Conservation and
Natural Resources at 334-242-3469 or my office at 334-240-7253 to
determine if any testing would be needed.
I want to
encourage sportsmen and women to continue enjoying the outdoors of Alabama
by hunting and rest assured of the safety of this great natural
resource.
Happy New
Year!
|
