or loss of condition without noticeable loss of appetite. Affected cattle die. The 

 causative agent of the disease is not completely characterized, and there is neither any 

 treatment nor a vaccine to prevent BSE. The incubation period is from 2 to 8 years. 

 Following the onset of clinical signs, the animal's condition deteriorates until it either 

 dies or is destroyed. This process usually takes from 2 weeks to 6 months. 



The preferred method for disposal of BSE-infected carcasses is incineration or 

 alkaline digestion. Under no circumstances should BSE suspects be used for human 

 or animal consumption. 



The Cause of BSE and Tissues Affected — Ihc agent responsible for BSE is 

 smaller than the smallest known virus and is extremely resistant to heat and to 

 normal sterilization processes. It also does not evoke any detectable immune response 

 or inflammatory reaction in host animals. 



Three main theories on the nature of the agent ha\e been advanced: ( 1 ) the agent is a 

 virus with unusual characteristics, (2) the agent is a prion (an exclusively host-coded 

 protein that is modified to a partially protease-resistant form after infection), and 

 (3) the agent is a virino (a small, noncoding regulat(H\ nucleic acid coated with a 

 host-derived protective protein). 



In cattle naturally infected with BSE, the BSE agent has been found onl\ in brain 

 tissue, in the spinal cord, and in the retina. In experimentally infected cattle, the 

 distal ileum, bone marrow, dorsal root ganglion, and trigeminal ganglion trom 

 experimentally infected cattle were also found to be infective. To date, no evidence 

 of infectivity has been detected in milk or muscle tissue. 



Testing — Currently, there is no test to detect the disease in a live animal. BSE is 

 confirmed b\' either histopathologic examination ol brain tissue or b\' the detection 

 of an abnormal protein called a prion via one of several methods that also require 

 brain tissue. BSE is so named because brain tissue taken from infected cattle looks 

 spongy when examined under a microscope. 



Epidemiologic data suggest that, in the United Kingdom, BSE is an extended 

 common-source epidemic involving animal feed containing contaminated meat-and- 

 bone meal as a protein source. There are different scientific hypotheses concerning 

 the origins of the disease. It may have been caused by feeding cattle rendered protein 

 produced from the carcasses of scrapie-infected sheep or cattle with a previously 

 unidentified TSE. There is no evidence that BSE spreads horizontally, that is, by 

 contact between unrelated adult cattle or contact between cattle and other species. 



Eradication and Control Efforts — Agricultural officials in the United Kingdom 

 and other countries affected with BSE have taken actions to eradicate or control the 

 disease. These entail prohibiting the inclusion of mammalian meat-and-bone meal 

 in animal feed; prohibiting the use of specified risk materials (those tissues, e.g.. 



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