Bse

Bovine Spongiform Encephalopathy or BSE, also known as Mad Cow disease, was first diagnosed in Great Britain in 1986. (1) BSE is another form of Transmissible Spongiform Encephalopathlies (TSE). TSE's are transmissible because they are capable of being spread from one animal to another. TSE's are spongiform because they cause the appearance of sponge like wholes in the brain. TSE's are encephalopathic because they are neurodegenerative diseases of the brain.(13) BSE is a progressive, fatal neurological disease of adult cattle that resembles scabies of sheep and goats. BSE also has been transmitted experimentally to pigs, sheep, mice, mink, Maraque monkeys, and marmosets. BSE has also been diagnosed in several species of captive ungulates including nyala, gemsbok, eland, Arabian Oryx, Kudu, Scimitar Oryx, Ankole Cow, and Bison. It has also been diagnosed in at least five species of felids including Puma, Cheetah, Ocelot, Lion, and Tiger. Only the United Kingdom has experienced a significant epidemic although other countries have had lower incident rates of BSE. Cattle populations in other countries have become infected as a result of the importation of meat and bone meal from countries with the disease.

The molecular nature of the disease of the disease causing agent is uncertain. The disease is associated with an abnormal form of a membrane protein, PrP(prionprotein). A hypothesis was formed for which this abnormal protein is assumed to be the infectious agent of the disease. BSE develops as the result of food borne exposure to contaminated meat and bone meal in feeding rations. There is no sex or breed disposition although there has some evidence suggesting a maternal link for calves of infected cows. The modal age at onset is -5 years and can span the commercial lifespan of the infected cattle. The pathogenesis of the disease is unknown, but studies indicate that that after oral ingestion of infected feed, the agent replicates in the Peyer's patches of the ileum followed by migration via the peripheral nerves to the Central Nervous System.

Initial clinical findings are subtle and are behavioral in nature. (8) Signs and symptoms of BSE in cattle include the following:

Affected cattle may display changes in temperament, such as nervousness or aggression;

Ð'* Abnormal posture;

Ð'* Poor coordination and difficulty in rising;

Ð'* Decreased milk production;

Ð'* Loss of body condition despite continued appetite;

Ð'* The incubation period ranges from 2 to 8 years;

Ð'* There is no treatment, and affected cattle die;

Ð'* Death generally occurs within 6 months of onset of the disease. (2)

Ð'* The spread of BSE is thought to be through feeding infected bone meal and feeding other high-risk materials such as spinal cords, brains, eyes, tonsils. The majority of BSE cases has been confirmed in the United Kingdom, but it has also been confirmed in the following countries:

Ð'* Belgium, Denmark, France, Germany, Italy, Ireland, Liechtenstein, Luxembourg, the Netherlands, Northern Ireland, Portugal, Spain, Switzerland, Japan, Austria, Finland, Greece, Czech Republic, Slovakia, and Slovenia. In addition, animals with BSE have been imported into Canada, Falkland Islands and Oman.(3) BSE has been detected in 182,000 cattle in more than 35,000 different herds in the UK since the first detection in 1986, and in more than 3800 cattle in other countries throughout the world. BSE is zoonotic but non-contagious because it is not excreted, thereby preventing horizontal transmission of the disease from animal to animal. It fits the definition of a production disease because its transmission is dependent on feed management practices.(13)

Ð'* The origin of the first BSE case remains a mystery, but transmission has been linked to the feeding of mammalian derived proteins through established rendering practices. One popular theory holds that BSE originated from the feeding of Meat and Bone meal contaminated with scrapies. Scrapies is another form of TSE that affects sheep. There are large numbers of infected sheep in the UK and the fact that sheep with scrapies was rendered together with cattle tends to support the theory. Feeding Meat and Bone meal from sheep back to cattle could have broke the species barrier. (13) (see table two)

Ð'* USDA announced on December 23, 2003 that a cow slaughtered on December 9, 2003, at a facility in Moses Lake, Washington had tested positive for BSE. The USDA determined that the cow originated from a herd in Mabton, Washington. The herd was placed under quarantine . The following day, USDA-FSIS issued a Class II meat recall of 10,410 pounds of beef generated from the 20 cows cows slaughtered with the BSE positive cow. It was determined that the BSE posive cow had been born in Alberta, Canada before the mammalian feed ban regulation of 1997. On December 27, 2003 Secretary of Agriculture Ann. M. Veneman announced the following actions:

Ð'* 1._ A ban on non-ambulatory disabled(downer) cattle from the human food chain

Ð'* 2.) A "test and hold" policy that mandates that meat from cattle tested for BSE be held until the test result is final

Ð'* 3).Removal of SRM's from the human food supply

Ð'* 4). Banning spinal cord and dorsal root ganglia from advanced meat recovery (AMR)

Ð'* 5). Ban on the use of Mechanically separated beef from the Human food supply

Ð'* 6). A ban on air injection stunning(13)

Ð'* June of 2005 a BSE was confirmed from a bovine animal born in the United States through additional tests conducted in England According to the press release the animal was blocked from entering the human food supply through the firewall system set up by USDA. This animal was born before the feed ban instituted by FDA. There has been an estimated total of 388,309 BSE tests of animals considered high risk conducted in the United States and only 3 times has there been an inconclusive screening result.(4)

Ð'* FDA FEED BAN

Ð'* was one of the first steps taken by the United States government. The ban on feeding of mammalian protein to ruminants was undertaken in 1997. Since the only discovered route in which BSE can be transmitted is the feeding of infected mammalian tissue, this regulation