Cambios

Also known as: '''''BSE — Mad Cow Disease'''''

También conocida como: '''''EEB - Enfermedad de las Vacas Locas'''''

==Introduction==

==Introducción==

[[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.]]

[[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.]]

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" />.  

La EEB fue reconocida por primera vez en Reino Unido en 1986 tras una gran epidemia  en la que se vieron envueltos más de 100.000 animales enfermos. Con la excepción de Francia y Portugal, el número de animales infectados en otros países se ha mantenido bajo. La enfermedad está ahora distribuida por todo el mundo y existen datos de casos producidos en Europa, Asia, Oriente Medio y América del Norte.

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.  

La encefalopatía espongiforme bovina (EEB) es una enfermedad '''nerviosa progresiva, mortal y no febril''' que afecta a los bovinos adultos. Pertenece a un grupo de enfermedades llamadas '''[[:Categoría:Encefalopatías Espongiformes Transmisibles|encefalopatías espongiformes transmisibles (EET)]]''', también conocidas como '''enfermedades priónicas'''. Puede ser causada por una enfermedad '''genética''' o '''infecciosa'''. Se produce cuando la conformación de los priones naturales PrP se transforma en la isoforma patógena PrP ^sc y produce degeneración espongiosa del cerebro. En las enfermedades priónicas genéticas, este hecho puede ser causado por una mutación somática en el gen PrP ^c. En la encefalopatía espongiforme bovina infecciosa, la exposición a un prion PrP ^sc  extraño puede iniciar este cambio de conformación, lo que da lugar a una cascada progresiva de cambios en la conformación de los priones naturales PrP ^c a PrP ^sc <ref name="Pruisiner, 1997" />.  

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'''.

El ganado se infectó por primera vez con los priones anormales a través de la alimentación con piensos que contenían proteínas derivadas de ingredientes tales como harina de carne y huesos (HCH) procedentes de rumiantes. Se cree que los cambios en el proceso de fabricación de HCH aumentaba la supervivencia de materiales similares a scrapie (priones) de las canales de ovino infectadas y el uso de despojos infectados de la misma especie bovina pudo conducir a la propagación de la EEB a través de la HCH infectada.

==Signalment==

No existen datos para afirmar la posibilidad de transmisión horizontal de la EEB en circunstancias naturales, pero hay datos que apoyan la '''transmisión vertical''' <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>. La EEB es una enfermedad de '''declaración obligatoria''' y a diferencia del [[Scrapie|scrapie]] se considera '''zoonosis'''.

 

==Características==

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==

==Signos Clínicos==

[[File:BSE 2.jpg|thumb|200px|right|A cow suffering from BSE - recumbent, low body condition score and difficulty rising.]]

[[File:BSE 2.jpg|thumb|200px|right|A cow suffering from BSE - recumbent, low body condition score and difficulty rising.]]

The first sign is usually '''separation from the herd''' and '''reluctance to move''' into the milking parlour and the cows may respond by with vigorous kicking.  

The first sign is usually '''separation from the herd''' and '''reluctance to move''' into the milking parlour and the cows may respond by with vigorous kicking.  

Other clinical signs include anorexia, weight loss, bruxism, ptyalism, trismus, pruritus, dull rough coat and ophthalmic signs including blindness, lacrimation, ptosis and prolapsed third eyelid.  

Other clinical signs include anorexia, weight loss, bruxism, ptyalism, trismus, pruritus, dull rough coat and ophthalmic signs including blindness, lacrimation, ptosis and prolapsed third eyelid.  

==Diagnosis==

==Diagnóstico==

A preliminary diagnosis can be made on observation of the above clinical signs. The disease is characterized by '''accumulation of prion protein in the medulla oblongata''' (obex) region of the brain, as well as other tissues (lymph nodes, spleen, tonsils, etc) and can be confirmed on post mortem by the presence of the following histological changes in the brain: bilateral symmetrical vacuolation and immunohistochemical demonstration of the accumulation of the disease specific PrP^sc in the grey matter of the brain, gliosis, hypertrophy of astrocytes, neuronal degeneration and cerebral amyloidosis.  

A preliminary diagnosis can be made on observation of the above clinical signs. The disease is characterized by '''accumulation of prion protein in the medulla oblongata''' (obex) region of the brain, as well as other tissues (lymph nodes, spleen, tonsils, etc) and can be confirmed on post mortem by the presence of the following histological changes in the brain: bilateral symmetrical vacuolation and immunohistochemical demonstration of the accumulation of the disease specific PrP^sc in the grey matter of the brain, gliosis, hypertrophy of astrocytes, neuronal degeneration and cerebral amyloidosis.  

   

   

'''Differential diagnosis''': hypomagnesemia, nervous acetonemia, [[Lead Poisoning|lead poisoning]], intracranial tumours, and infectious diseases such as [[Rabies|rabies]], [[listeriosis]] , [[Aujeszky's Disease|Aujeszky’s disease]] and cerebro-cortical-necrosis (CCN).

'''Differential diagnosis''': hypomagnesemia, nervous acetonemia, [[Lead Poisoning|lead poisoning]], intracranial tumours, and infectious diseases such as [[Rabies|rabies]], [[listeriosis]] , [[Aujeszky's Disease|Aujeszky’s disease]] and cerebro-cortical-necrosis (CCN).

==Treatment==

==Tratamiento==

There is currently no vaccine or treatment protocol for this disease.

Actualmente no existe una vacuna o protocolo de tratamiento para esta enfermedad.

==Control==

==Control==