bovine spongiform encephalopathy by bishajit
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BISHAJIT DEBNATHID. -113-079-031
Bovine Spongiform Encephalopathy
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It was first described in Britain in 1986.
The disease is considered to have spread from Great Britain from export of contaminated Meat-and-Bone-Meal(MBM) in Europe(19 countries reported at least one case of non imported cattle) plus Israel and Japan.
BSE was first recognized in the UK in 1988 , which has the highest yearly incidence of the disease, from its discovery to 2002 more than 180,000 cases were reported.
History of Disease
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A fatal prion disease of cattle that affects the nervous system,
resembles or is identical with scrapie of sheep and goats, and is probably transmitted by infected tissue in food called also mad cow disease.
BOVINE SPONGIFORM ENCEPHALOPATHY
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The infectious agent in BSE is believed to be a specific type of misfolded protein called a prion.
Prion = Proteinaceous infectious particle Normal Protein: PrPC (C for cellular)
Prion proteins carry the disease between individuals and cause deterioration of the brain.
BSE is a type of transmissible spongiform encephalopathy (TSE)
CAUSATIVE AGENT OF BSE
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The natural hosts are cattle.
Some cases have also occurred in antelopes and feline (cats, tiger, puma etc).
A range of other species including mice, pigs, and sheep has been infected experimentally.
Humans are thought to be susceptible (vCJD).
Susceptible species
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United Kingdom£3.7 billion total by end of 2001-02In 1996-97
£850 million for compensationPrior to 1996
£288 million on research, surveillance, compensation
Very costly, far reaching disease
Economic Impact
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Reasons for emergence
- Feed contaminated with scrapie or unknown BSE - Spontaneous - Changes in feed processing
Maternal transmission - Possible, low risk - Retrospective offspring culling
Current thought - Spread via ingestion of BSE contaminated feed
Animal Transmission
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Humans consuming cattle products infected with BSE can develop vCJD
◦ Brain and spinal tissue
Consumption of milk and milk products
Dose required not known
Genetic susceptibility
◦ All human cases have been homozygous for methionine at codon 129 of PrPC
Human Transmission
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DEPARTMENT OF MICROBIOLOGY, PRIMEASIA UNIVERSITY
Incubation: 2-8 years
Initial neurological signs◦ Apprehension, fear, easily startled, depressed
Final stages
Excitable, hyperreflexia, hypermetria, ataxia, muscle fasciculation, tremors.
Autonomic dysfunction: reduced rumination, bradycardia and altered heart rhythm
Hyperesthesia or hyperreflexia.
Incubation Period and clinical Sign
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Terminal state
◦ Decreased rumination◦ Loss of body weight and condition, despite good appetite
There is no treatment for BSE
Affected herds
◦ 2-3% morbidity◦ 100% mortality
Visible Sign and Treatment
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The BSE testing protocol calls for an initial rapid test called an Enzyme-Linked Immunosorbent Assay (ELISA).
If the ELISA test is inconclusive, samples are sent for confirmatory testing to the National Veterinary Services Laboratories (NVSL).
An immunohistochemistry test is conducted at NVSL and, concurrently, an OIE-approved Western Blot is conducted at the National Animal Disease Center (NADC).
These tests are designed to detect the presence of BSE-specific abnormal prion protein in the brain tissue.
DIAGNOSIS
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June 24, 2005
- New BSE confirmatory testing protocol
IHC & Western Blot
confirmatory tests
Positive result on either test considered positive for BSE
“Inconclusive” BSE rapid screening tests.
Post Mortem Tests for BSE
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No effective treatment or vaccine
Surveillance program
Blood/plasma donation restrictions
USDA bans importation of ruminants from countries with BSE.
Persons who have traveled or resided in the U.K. for 3 or more cumulative months from 1980 to 1996.
Vaccination/Prevention
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Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a fatal neurodegenerative disease (encephalopathy) in cattle that causes a spongy degeneration in the brain and spinal cord.
The infectious agent, although most highly concentrated in nervous tissue, can be found in virtually all tissues throughout the body, including blood.
CONCLUSION
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THANK YOU
DEPARTMENT OF MICROBIOLOGY, PRIMEASIA UNIVERSITY