1. Presented by hadah al- khaldi
mad caw disease
Presented by
hadah al- khaldi

2. History of Mad Cow Disease:
BSE, or bovine spongiform encephalopathy, was first noticed in the United Kingdom in Cattle became infected with this disease as a result of being fed ground up sheep parts, which were contaminated with scrapie, a common disease among sheep. As a result of the public's demand for cheap food, the meat industry has been forced to increase their milk and meat yield in a way which does not cost a lot for the industry or the consumer. This involved giving the cattle, who are normally herbivores, a protein-based feed made from animal offal (innards). The disease was able to survive in the sheep offal, even after being subjected to extreme temperatures during processing procedures of the feed. Therefore, this disease was able to transmit from the sheep population to cattle.

3. Transmission:
it can be transmitted from one animal species to another. Scrapie and BSE come from the same type of disorder, spongiform encephalopathy, but are found in two different species. Further experimentation has shown that it can be transmitted to other animals, such as mice, monkeys, pigs, and felines as well. For many years zoo animals were fed protein supplements made from the offal of British cattle.

4. Even though the use of British beef for food supplements was banned in 1996, effects are still being seen. As recently as March 1999, monkeys and lemurs in French zoos have been identified as infected with a form of spongiform encephalopathy. These animals had not been fed offal from British cattle for three years, but as a result of the long incubation period of this type of disorder, from 2 to 8 years, these animals, who previously appeared healthy, are now showing symptoms similar to BSE. This evidence illustrates how easily the disease can be transmitted from one animal species to another, but BSE becomes a greater problem when it poses a threat to humans.

5. Human Risks:
What is the risk that BSE will infect humans?
It appears the risk of infection is dependent on:
Susceptibility to infective agent. Susceptibility depends on both species differences and within species protein sequence variations.
Dose of infective agent.

6. Infectivity of bovine tissues and body fluids
Highest infectivity
brain
spinal cord
eye
Medium infectivity
spleen
tonsil
lymph node
ileum
proximal and distal colon
pituitary gland
adrenal gland
cerebrospinal fluid
placenta
pineal gland

7. Low infectivity
peripheral nerve
liver
lung
pancreas
bone marrow
thymus
nasal mucosa
No infectivity
skeletal muscle (meat)
heart
mammary gland - milk, colostrum
blood - blood clot, serum or plasma
kidney
thyroid gland
salivary gland
ovary
uterus
testis
seminal vesicle
fetal tissues
hair
skin
bone
cartilaginous tissue
connective tissue
bile
saliva
urine
feces

8. What is Mad Cow Disease?
Mad cow disease, or bovine spongiform encephalopathy (BSE), is a fatal brain disorder that occurs in cattle and is caused by some unknown agent. In BSE, the unknown agent causes the cow's brain cells to die, forming sponge-like holes in the brain. The cow behaves strangely and eventually dies. The connection between BSE and humans was uncovered in Great Britain in the 1990s when several young people died of a human brain disorder,

9. The Disease Causing Agent
The disease appears to be caused by an unconventional infectious agent, originally believed to be a "slow virus," a "self-replicating protein.
Recently the causitive agent was found to be an abnormal conformation form (PrPsc) of a normally occurring protien (PrP). PrP is the abbreviation used to identify the normal "prion" protein. This agent is extremely resistant to heat and to normal sterilization processes. PrPsc does not evoke a detectable immune response or inflammatory reaction in host animals.

10. Why is the manifest late?
Takes time to switch to infectious PrP.
Takes time to infect other normal PrP.
Takes time to cause brain damage
What is the PrP?
The prion protein, PrP, is a normal cell protein present on nerve cell membranes. The gene for PrP is present in most mammals. However, PrP's normal function is unclear; mice without the protein appear to be fine.

11. PrP's amino acid sequences are highly conserved across species (>85% identity between human, mouse, sheep and cattle). This similarity permits PrP from one species to interact with PrP from another species (a requirement for infectivity)
Resistance of PrPsc
. Some loss of infectivity occurs at temperatures above 100°C

12. Electron Microscopy of a Prion

13. PrP
PrPsc
Structure high in alpha-helix.
Structure high in beta-structure.
Protease susceptible.
Core residues are protease resistant.
Monomeric species.
Forms multimeric aggregates.

14. We don't know the agent that causes BSE, but we do know the following
The agent's size must be as small or smaller than a virus.
You can't kill it by cooking or freezing
Disinfectants don't work
It does not appear to have genetic information

15. Pathology: Movement of PrP following oral exposure
1) PrPsc enters the body when foods are consumed
- MBM for BSE.
2) PrPsc pass through the
- Esophagus into
- Acidity of the stomach
- And the destructive enzymes of the small intestine
Enough PrPsc may remain intact to be absorbed and cause infection.
PrPsc traverse the intestine going into lymph nodules ( Peyer’s patches ) of
the distal intestine (ileum).
PrPsc may replicate in follicular dendritic cell of the Peye’s patches.
Most of the other proteins consumed are converted to small polypeptides or
into fee amino acids before being absorbed and entering the blood or lymph
systems. .

16. - Follicular dendritic cells.
3) PrPsc are transferred to the spleen and are found on the surface of
- T lymphocytes.
- B lymphocytes.
- Follicular dendritic cells.
PrPsc probably proliferate here before infecting the nervous system.
Without involvement of the lymphoreticular system or during
Immunodepression, infection is possible but impaired.
Stimulation of B and cells or immune system enhances infection
4) Despite the presence of B and T lymphocytes in the circulation, neither
blood nor most peripheral tissues containing and continuously exposed
to blood are infectious.
5) PrPsc eventually establish and multiply within the brain and spinal cord
forming plaques, killing nervous and disrupting brain function.

17. The main sites affected are:
1) Thalamus.
2) Cerebllum.
Clinical signs of BSE include:
abnormally stilted gait
high stepping
heightened sensory perception
itching
anorexia
excessive licking
death.

18. Diseases caused by infected prion protein:
Prion diseases are often called spongiform encephalopathies because of the post mortem appearance of the brain with large vacuoles in the cortex and cerebellum. Probably most mammalian species develop these diseases. Specific examples include:
Scrapie: sheep
TME (transmissible mink encephalopathy): mink
CWD (chronic wasting disease): muledeer, elk
BSE (bovine spongiform encephalopathy): cows

19. Control and Prevention
avoid beef and beef products altogether.
if eating meat, then select beef or beef products that have less opportunity for contamination from nervous tissue (solid muscle cuts vs. processed sausages or hamburgers).
milk or milk products are not believed to pose any risk from the BSE agent.
Diagnostic Tests and Surveillance
There is no approved laboratory test able to detect the disease in live animals. Veterinary pathologists confirm BSE by microscopic examination of brain tissue.

21. New enzyme can destroy mad cow disease protein
KAGOSHIMA (Kyodo) A Kagoshima University research team has discovered a new enzyme that is capable of breaking down a protein particle believed to be the transmitter of mad cow disease, university sources said Saturday.
Treatment / Cure?
There is no cure for BSE or CJD

22. Thank You