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Also known as: '''''BSE — Bovine Spongiform Encephalopathy''''', '''''TSE — Transmissible Spongiform Encephalopathy'''''', '''''Mad Cow Disease''''', '''''Scrapie — a transmissible prion affecting sheep that causes non-febrile neurological disease''''', '''''PrP - (Prion protein) proteinaceous infectious particle''''', '''''PrP^ab — Abnormal Prion Protein''''',  '''''PrP^res —  Resistant Prion Protein'''''',  '''''PrP^sc —  Scrapie Prion Protein'''''  

Also known as: '''''BSE — Bovine Spongiform Encephalopathy — Mad Cow Disease'''''

==Introduction==

==Introduction==

[[File:Histology BSE.jpg|thumb|200px|left|This micrograph of brain tissue reveals the cytoarchitectural histopathologic changes found in bovine spongiform encephalopathy. The presence of vacuoles, i.e. microscopic “holes” in the grey matter, gives the brain of BSE-affected cows a sponge-like appearance when tissue sections are examined in the lab.]]

[[File:Histology BSE.jpg|thumb|200px|right|This micrograph of brain tissue reveals the cytoarchitectural histopathologic changes found in bovine spongiform encephalopathy. The presence of vacuoles, i.e. microscopic “holes” in the grey matter, gives the brain of BSE-affected cows a sponge-like appearance when tissue sections are examined in the lab.]]

BSE was first recognised in the United Kingdom in 1986 after a huge epidemic in the UK involving over 100,000 diseased cattle. With the exception of France and Portugal, the number of infected animals in other countries has remained low. The disease is now worldwide and has occurred in Europe, Asia, Middle East and North America.  

BSE was first recognised in the United Kingdom in 1986 after a huge epidemic in the UK involving over 100,000 diseased cattle. With the exception of France and Portugal, the number of infected animals in other countries has remained low. The disease is now worldwide and has occurred in Europe, Asia, Middle East and North America.  

Bovine spongiform encephalopathy (BSE) is a progressive, fatal and non-febrile neurological disorder affecting adult cattle. BSE belongs to a group of diseases called transmissible spongiform encephalopathy (TSE) and other TSE’s include Creutzfeldt-Jakob disease in humans, scrapie in sheep, chronic wasting disease (CWD) in  elk and deer and feline spongiform encephalopathy has been found within cats in the UK.   BSE is a prion disease and can be caused by an infectious or genetic disorder.  It occurs when a natural prion PrP changes in conformation into the pathogenic isoform PrP^sc and causes the spongy degeneration of the brain. In genetic prion diseases, this may be caused by a somatic mutation in the PrP^c gene or in infectious BSE, exposure to foreign PrP^sc may start this  conformation, leading to a progressive cascade of conformational change of natural PrP^c into PrP^sc <ref name="Pruisiner, 1997" />. Cattle became exposed to the abnormal prions through the feeding of ruminant-derived protein within feedstuffs such as meat-and-bone meal (MBM). It is thought that changes in the rendering process of the MBM increased the survival of scrapie-like materials (prions) from infected sheep carcasses and the recycling of infected bovine materials lead to the spread of BSE through infected MBM. There is no evidence to support the horizontal transmission of BSE under natural circumstances but there is evidence supporting vertical transmission <ref name="Wilesmith 1997">Wilesmith, J.W., Ryan,  J.B.M., 1997. Absence of BSE in the offspring of pedigree suckler cows affected by BSE in Great Britain. Veterinary Record, 141(10):250-251; 5 ref.</ref>, <ref name="Donnelly 1998">Donnelly ,C.A., 1998. Maternal transmission of BSE: interpretation of the data on the offspring of BSE-affected pedigree suckler cows. Veterinary Record, 142(21):579-580; 9 ref..</ref>, <ref name="Fatzer 1998">Fatzer,  R., Ehrensperger,  F., Heim,  D., Schmidt,  J., Schmitt,  A., Braun,  U., Vandevelde,  M., 1998. Investigation of 182 offspring of cows with bovine spongiform encephalopathy (BSE) in Switzerland. Part 2. Epidemiological and neuropathological results. Schweizer Archiv für Tierheilkunde, 140(6):250-254; 14 ref.</ref>, <ref name="Schreuder, 1998">  Schreuder BEC, 1998. Epidemiological aspects of scrapie and BSE including a risk assessment study. ISBN 90-393-1636-8. Thesis University of Utrecht..</ref>, <ref name="OIE 2000">OIE, 2000. Bovine spongiform encephalopathy. In: OIE Manual of Standards for diagnostic tests and vaccines. Office International des Epizooties, edition 4, 457-460.</ref>.  BSE is notifiable and unlike scrapies is considered a zoonosis.

 

Bovine spongiform encephalopathy (BSE) is a '''progressive, fatal and non-febrile neurological''' disorder affecting adult cattle. BSE belongs to a group of diseases called '''[[:Category:Transmissible Spongiform Encephalopathies|transmissible spongiform encephalopathy (TSE)]]''', also referred to as '''prion diseases'''. It can be caused by an '''infectious''' or '''genetic''' disorder.  It occurs when a natural prion PrP changes in conformation into the pathogenic isoform PrP^sc and causes the spongy degeneration of the brain. In genetic prion diseases, this may be caused by a somatic mutation in the PrP^c gene or in infectious BSE, exposure to foreign PrP^sc may start this  conformation change, leading to a progressive cascade of conformational change of natural PrP^c into PrP^sc <ref name="Pruisiner, 1997" />.  

 

Cattle became exposed to the abnormal prions through the feeding of ruminant-derived protein within feedstuffs such as meat-and-bone meal (MBM). It is thought that changes in the rendering process of the MBM increased the survival of scrapie-like materials (prions) from infected sheep carcasses and the recycling of infected bovine materials lead to the spread of BSE through infected MBM.  

 

There is no evidence to support the horizontal transmission of BSE under natural circumstances but there is evidence supporting '''vertical transmission''' <ref name="Wilesmith 1997">Wilesmith, J.W., Ryan,  J.B.M. (1997) '''Absence of BSE in the offspring of pedigree suckler cows affected by BSE in Great Britain.''''' Veterinary Record,'' 141(10):250-251; 5 ref.</ref>, <ref name="Donnelly 1998">Donnelly ,C.A. (1998) '''Maternal transmission of BSE: interpretation of the data on the offspring of BSE-affected pedigree suckler cows.''''' Veterinary Record,'' 142(21):579-580; 9 ref..</ref>, <ref name="Fatzer 1998">Fatzer,  R., Ehrensperger,  F., Heim,  D., Schmidt,  J., Schmitt,  A., Braun,  U., Vandevelde,  M. (1998) '''Investigation of 182 offspring of cows with bovine spongiform encephalopathy (BSE) in Switzerland. Part 2. Epidemiological and neuropathological results.''''' Schweizer Archiv für Tierheilkunde,'' 140(6):250-254; 14 ref.</ref>, <ref name="Schreuder, 1998">  Schreuder BEC (1998) '''Epidemiological aspects of scrapie and BSE including a risk assessment study.''' ISBN 90-393-1636-8. ''Thesis University of Utrecht''</ref>, <ref name="OIE 2000">OIE (2000) '''Bovine spongiform encephalopathy. In: OIE Manual of Standards for diagnostic tests and vaccines.''''' Office International des Epizooties'' (edition 4), 457-460.</ref>.  BSE is '''notifiable''' and unlike [[Scrapie|scrapie]] is considered a '''zoonosis'''.

==Signalment==

==Signalment==

The disease has a very long incubation period (average  4 – 5 years ) and mainly affects animals aged 4-6 years old.  It causes progressive neurological signs which can last several months and results in mortality. There is no breed or sex predilection, however the incidence of BSE in dairy cows is much greater than beef cows, possibly correlated to the greater use of concentrate rations containing MBM.   

The disease has a '''very long incubation period''' (average  4 – 5 years ) and mainly affects animals aged 4-6 years old.  It causes progressive neurological signs which can last several months and results in mortality. There is no breed or sex predilection, however the '''incidence of BSE in dairy cows is much greater than beef cows''', possibly correlated to the greater use of concentrate rations containing MBM.  

Spongiform encephalopathies also occurred in new species such as the greater kudu, nyala, Arabian onynx, Scimitar horned oryx, eland, gemsbok, bison, ankole, tiger, cheetah, ocelot, puma, and domestic cats, during the 1990s  <ref name="Benbow, 1990">Benbow, G.M., 1990. Zoo animal BSE. Vet. Rec., 126:441. </ref>,  <ref name="Collinge, 2001">Collinge, J., 2001. Prion diseases of humans and animals: their causes and molecular basis. Ann. Rev. Neurosci., 24:519-550.</ref> ,  <ref name="Pruisiner, 1997">Prusiner, S.B., 1997. Prion diseases. In: Viral pathogenesis. Nathanson, et al., eds. Philadelphia, USA: Lippin-Cott-Raven Publishers, 871-911.</ref>  and in 2005 a goat was confirmed positive for BSE in France. To date there is no scientific evidence that experimental oral BSE challenge of pigs and poultry with brain material from cattle with BSE results in disease.

    

Spongiform encephalopathies also occurred in new species such as the greater kudu, nyala, Arabian onynx, Scimitar horned oryx, eland, gemsbok, bison, ankole, tiger, cheetah, ocelot, puma, and domestic cats, during the 1990s  <ref name="Benbow, 1990">Benbow, G.M. (1990) '''Zoo animal BSE.''''' Vet. Rec.'' 126:441. </ref>,  <ref name="Collinge, 2001">Collinge, J. (2001) '''Prion diseases of humans and animals: their causes and molecular basis.''''' Ann. Rev. Neurosci.'' 24:519-550.</ref> ,  <ref name="Pruisiner, 1997">Prusiner, S.B. (1997) '''Prion diseases. In: Viral pathogenesis. Nathanson, et al., eds. Philadelphia, '''''USA: Lippin-Cott-Raven Publishers,'' 871-911.</ref>  and in 2005 a goat was confirmed positive for BSE in France. To date there is no scientific evidence that experimental oral BSE challenge of pigs and poultry with brain material from cattle with BSE results in disease.

==Clinical Signs==

==Clinical Signs==

==Refereneces==

==Refereneces==

<references/>

<references/>

[[Category:Transmissible_Spongiform_Encephalopathies]]

[[Category:Transmissible_Spongiform_Encephalopathies]]

[[Category:To_Do_-_CABI review]]

[[Category:To_Do_-_CABI review]]