Өвчний тодорхойлолт, үүсгэгч шалтгаан, эмгэг жам, эмнэл зүйн шинж тэмдэг

1. Сэдэв 6: Прионы өвчнүүд
• Тархи нугасны эд сархиагтах халдварт эмгэг
• Үхрийн тархины эд сархиагтах эмгэг
• Хонины скрепи

2. • Prion diseases or transmissible spongiform encephalopathies
(TSEs) are a family of rare progressive neurodegenerative
disorders that affect both humans and animals.
• They are distinguished by
 long incubation periods;
 characteristic spongiform changes associated with neuronal
loss;
 and a failure to induce inflammatory response.
DEFINITION OF DISEASE

3. • The causative agents of TSEs are believed to be prions.
• The term “prions” refers to abnormal, pathogenic agents that
are transmissible and are able to induce abnormal folding of
specific normal cellular proteins called prion proteins that are
found most abundantly in the brain.
• The functions of these normal prion proteins are still not
completely understood.
• The abnormal folding of the prion proteins leads to brain
damage and the characteristic signs and symptoms of the
disease.
• Prion diseases are usually rapidly progressive and always fatal.
CAUSATIVE AGENTS

4. Identified Prion Diseases
• Listed below are the prion diseases identified to date.
Human Prion Diseases
• Creutzfeldt-Jakob Disease (CJD)
• Variant Creutzfeldt-Jakob Disease (vCJD)
• Gerstmann-Straussler-Scheinker Syndrome
• Fatal Familial Insomnia
• Kuru

5. Animal Prion Diseases
• Bovine Spongiform Encephalopathy (BSE)
• Chronic Wasting Disease (CWD)
• Scrapie
• Transmissible mink encephalopathy
• Feline spongiform encephalopathy
• Ungulate spongiform encephalopathy

6. Research indicates that the first probable infections of BSE in cows
occurred during the 1970’s with two cases of BSE being identified in
1986. BSE possibly originated as a result of feeding cattle meat-and-bone
meal that contained BSE-infected products from a spontaneously
occurring case of BSE or scrapie-infected sheep products.
BSE

7. The BSE epizootic in the United Kingdom peaked in January 1993 at almost
1,000 new cases per week. Since then, the annual numbers of BSE cases in
the United Kingdom have dropped sharply—
 2 cases in 2015
 11 cases in 2010
 225 cases in 2005
 1,443 cases in 2000
 14,562 cases in 1995
Cumulatively, through the end of 2015, more than 184,500 cases of BSE had
been confirmed in the United Kingdom alone in more than 35,000 herds.

8. Strong epidemiologic and
laboratory evidence exists for a
causal association between a
new human prion disease
called variant Creutzfeldt-Jakob
disease (vCJD) that was first
reported from the United
Kingdom in 1996 and the BSE
outbreak in cattle.

9. Control Measures
Public health control measures, such as surveillance, culling
sick animals, or banning specified risk materials, have been
instituted in many countries, particularly in those with
indigenous cases of confirmed BSE, in order to prevent
potentially BSE-infected tissues from entering the human
food supply.
The most stringent control measures include a UK program
that excludes all animals more than 30 months of age from
the human food and animal feed supplies. The program
appears to be highly effective.

10. Prevention
To prevent BSE from entering the United States, severe
restrictions were placed on the importation of live
ruminants, such as cattle, sheep, and goats, and certain
ruminant products from countries where BSE was known
to exist. These restrictions were later extended to include
importation of ruminants and certain ruminant products
from all European countries.

11. On August 23, 2001, the Department of Health and Human Services (HHS)
issued a department-wide action plan outlining steps to improve scientific
understanding of BSE and other transmissible spongiform encephalopathies
(TSEs). The action plan has four major components:
 Surveillance for human disease is primarily the responsibility of CDC.
 Protection is primarily the responsibility of the Food and Drug
Administration (FDA).
 Research is primarily the responsibility of the National Institutes of Health
(NIH).
 Oversight is primarily the responsibility of the Office of the Secretary of
DHHS.

12. Strains of BSE
There is increasing evidence that there are different strains
of BSE:
• the typical or classic BSE strain responsible for the
outbreak in the United Kingdom and
• two atypical strains (H and L strains).

13. CWD in Animals
CWD is a
progressive, fatal
disease that affects
the brain, spinal
cord, and many
other tissues of
farmed and free-
ranging deer, elk,
and moose.

14. • Like other prion diseases, CWD may have an incubation period of over a
year and clear neurological signs may develop slowly.
• Deer, elk, reindeer, sika, and moose with CWD may not show any signs of
the disease for years after they become infected.
• As CWD progresses, infected animals may have a variety of changes in
behavior and appearance. These may include:
 drastic weight loss (wasting)
 stumbling
 lack of coordination
 listlessness
 drooling
 excessive thirst or urination
 drooping ears
 lack of fear of people

15. Scrapie
• Scrapie is one of the diseases called transmissible spongiform
encephalopathies (TSEs) or ‘prion’ diseases.
• These diseases have long incubation periods during which an
abnormal protease-resistant isoform of a prion protein
accumulates in the central nervous system.

16. World distribution of scrapie
• Scrapie is present in several European Union member states,
especially the United Kingdom, Canada, the United States,
Iceland, India, Japan and Brazil. Israel has also reported
outbreaks of scrapie, with the most recent being in early 2007.
• There have been isolated reports of scrapie from a number of
countries including New Zealand (1954) and the Republic of
South Africa (1972). In these instances, the disease was confined
to imported sheep and was eradicated by destruction of the
affected group.
Scrapie

17. Atypical scrapie is a different disease to ‘classical’ scrapie
Atypical scrapie is a non-contagious, sporadic, degenerative brain condition
which can arise spontaneously in older sheep and, less commonly, in goats.
Atypical scrapie is a separate disease to classical scrapie. Atypical scrapie has
been diagnosed in more than 20 countries worldwide. Most countries
that test large numbers of sheep for classical scrapie have found cases of
atypical scrapie.
Scrapie

18. • Sheep that develop atypical scrapie show neurological signs
such as lack of coordination, head pressing and circling.
• Veterinarians should routinely submit samples from sheep
exhibiting neurological signs
• Atypical scrapie does not require OIE notification and cases
do not impact on trade.
Scrapie