Changes

==Clinical Signs==

==Clinical Signs==

[[File:BSE 2.jpg|thumb|200px|left|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. BSE-affected cattle show '''progressive neurological and behavioural changes''', abnormalities of posture and movement, recumbency, '''changes in sensation and temperament''' and increased aggression.  Nervousness, tremors, falling, hyperaesthesia to sound and touch and '''progressive weakness and hind-limb ataxia''' and agalactia or '''decreased milk yield''' are the most prominent clinical signs. 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.  

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.  

For countries that are BSE free, preventative measures are ruminant to ruminant feed ban, import controls and surveillance.

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. 

For surveillance, a number of rapid tests on brain samples have been developed and approved by the European Union. These include the Western Blot test (detection of PrP^res),  Luminescence immunoassay (detection of disease specific prion proteins), and Chemiluminescent ELISA test.

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

To reduce the risk to humans developing variant Creutzfeldt-Jakob Disease (vCJD) all visible nervous

 

and lymphatic tissue that are classified as '''specified risk materials (SRM) are removed''' during the processing of cattle as well as the removal of any suspect animals from the human food chain.   

 

BSE is extremely difficult to control due to its long incubation period and the fact that the altered prions are extremely resistant to heat and chemicals.  Stringent preventive measures are in place to stop the spread of the disease, prevent cattle and human exposure and to eradicate BSE from the animal population.  The most important of these measures has been the feed ban issued in 1988, prohibiting the feeding of ruminant derived meat and bone meal (MBM) to ruminants <ref name= Hoinville, 1994">Hoinville, L.J. (1994) '''Decline in the incidence of BSE in cattle born after the introduction of the 'feed ban'.''''' Veterinary Record,'' 134(11):274-275; 12 ref.</ref> and the adoption of the ban by the EU in 1994.  Post mortem testing schemes and culling of infected cohort animals have also helped to reduce the spread of BSE.  So far they have resulted in a significant decrease in the number of BSE cases in the UK and other affected countries. Currently, the number of cases in the UK is decreasing.

For countries that are BSE free, preventative measures are ruminant to ruminant feed ban, import controls and surveillance.

Specified risk material of ''cattle'' includes: brain, eyes (retina), trigeminal ganglia, the spinal cord, the dorsal root ganglia, mesentery, intestines (duodenum to rectum) and tonsils.

[http://www.oie.int/en/animal-health-in-the-world/official-disease-status/bse/ List of Member Countries' BSE risk status from the World Organisation for Animal Health (OIE)]

SRM in ''sheep and goats'' include: spleen, ileum, spinal cord, brain, eyes and tonsils.

In 1996, cattle over the age of 30 months were eliminated from the food chain within the UK under the '''‘over thirty months scheme’''' (OTMS).  This ban has now been lifted and it is now compulsory to test all cattle over the age of 48months for BSE.

and lymphatic tissue that are classified as specified risk materials (SRM) are removed during the processing of cattle as well as the removal of any suspect animals from the human food chain.  Specified risk material of cattle includes: brain, eyes (retina), trigeminal ganglia, the spinal cord, the dorsal root ganglia, mesentery, intestines (duodenum to rectum) and tonsils.  SRM in sheep and goats include: spleen, ileum, spinal cord, brain, eyes and tonsils.  In 1996, cattle over the age of 30 months were eliminated from the food chain within the UK under the ‘over thirty months scheme’ (OTMS).  This ban has now been lifted and it is now compulsory to test all cattle over the age of 48months for BSE.

==Refereneces==

==Refereneces==

[http://www.oie.int/en/animal-health-in-the-world/official-disease-status/bse/ BSE disease distribution map and further information from the World Organisation for Animal Health (OIE)]

[http://www.oie.int/en/animal-health-in-the-world/official-disease-status/bse/ BSE disease distribution map and further information from the World Organisation for Animal Health (OIE)]

 

 

[[Category:Transmissible_Spongiform_Encephalopathies]]

[[Category:Transmissible_Spongiform_Encephalopathies]]

[[Category:Neurological Diseases - Cattle]]

[[Category:Neurological Diseases - Cattle]]

[[Category:Zoonoses]]

[[Category:Zoonoses]]

[[Category:To_Do_-_CABI review]]

[[Category:CABI Expert Review]]