Chronic wasting disease (CWD)
It is significant in prion disease. It affects in farmed animals and wild animals. It is prion disease of white-tailed deer, mule and
randomly in moose. It was discovered in 1970 by E.S Williams. It is exotic
disease. It is contagious. It is endemic in world. It was analyzed at Colorado
Division of Wildlife Foothills Wildlife Research. It spreads due to shortage of
food and stress. Mostly it has occurred in USA.
 |
| Chronic wasting disease (CWD) |
Pathology
It came from experimented infected animals. It causes
gradually weight loss. It changes behavior such as isolation and depression in
animals. Hypersalivation, odontoprisis, esophageal dilation, ataxia with head
tumor, regurgitation, aspiration pneumonia and polyuria are symptoms.
Environmental stress cause death. In central nervous system lesions are
appeared in gray matter. Hypertrophy, neuronal degeneration and astrocytic
hyperplasia can be appeared. Amyloid plaques are observed by hematoxylin-eosin
staining of brain. Vacuoles surrounds the brain cells. Immunohistochemistry
provides better result to observe spongiform. In brain, spinal cord, nerves,
ganglia, endocrine tissues and lymph nodes CWD accumulate. Vagus nerve is
affected extremely. Prions also start to grow in skeletal muscle. In saliva,
blood, urine prions present.
Prions in Environment
CWD is captive. Horizontal transmission to wild herds are
high. CWD also effect cervids of skeletal muscle. Fungi enzymes, heat,
proteases, chemical disinfectants, UV radiations, soil inhabitants digesters
and by mineral phases prion dispersed. In aquatic areas prion also travel to
mineral and metal deposits. It is spread from infected animals through help of
forage and water sources. In food, water and bedding prion can be observed.
Cervids are present on apical skin layer. Soil contamination can cause CWD.
Transmission
It is highly contagious disease. It can be transmitted from
infected saliva, feces and urine. It was not identified that what exactly
natural source of CWD. CWD is spontaneous disease of cervids. BSE is possible
source of sheep scrapie. By intracerebral inoculation sheep scrapie prion
spread disease to elk. At polymorphic codon diseased elk can be heterozygous or
homozygous. Minimize transmission of CWD is in cattle. Wolves, coyotes and
bears can get this disease.
CWD strains
In different animals and different incubation periods
different CWD strains are present. Spongiform lesions variation is difficult to
identify. It has been confirmed that there are two strains of CWD.
Diagnosis
At the starting of this disease there are no symptoms that’s
why it is difficult to identify. In later stages of this disease symptoms are
severe. There is progressive weight loss, hypersalivation, ataxia and
polydipsia in later stages. Immunohistochemistry, ELISA test are performed to
detect CWD. Amplification methods are done to observe prions. Ultrasensitive
immunoassays and antibodies are used to detect infection.
Treatment
This disease is fatal. There are no vaccines and
prophylactic treatment available.
Prevention
It is impossible to control CWD. In future it is difficult to eradicate. It is needed to clean environment. Public awareness is necessary. And during handling the meat wear rubber gloves.