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Bovine spongiform encephalopathy
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Bovine spongiform encephalopathy
Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is an incurable and always fatal neurodegenerative disease of cattle. Symptoms include abnormal behavior, trouble walking, and weight loss. Later in the course of the disease, the cow becomes unable to function normally. There is conflicting information about the time between infection and onset of symptoms. In 2002, the World Health Organization suggested it to be approximately four to five years. Time from onset of symptoms to death is generally weeks to months. Spread to humans is believed to result in variant Creutzfeldt–Jakob disease (vCJD) or Creutzfeldt–Jakob disease (CJD). As of 2024[update], a total of 233 cases of vCJD had been reported globally.
BSE is thought to occur due to an infection by a misfolded protein, known as a prion. Cattle are believed to have been infected by being fed meat-and-bone meal that contained either the remains of cattle who spontaneously developed the disease or scrapie-infected sheep products. The United Kingdom was afflicted with an outbreak of BSE and vCJD in the 1980s and 1990s. The outbreak increased throughout the UK due to the practice of feeding meat-and-bone meal to young calves of dairy cows. Cases are suspected based on symptoms and confirmed by examination of the brain. Cases are classified as classic or atypical, with the latter divided into H- and L types. It is a type of transmissible spongiform encephalopathy.
Efforts to prevent the disease in the UK include not allowing any animal older than 30 months to enter either the human food or animal feed supply. In continental Europe, cattle over 30 months must be tested if they are intended for human food. In North America, tissue of concern, known as specified risk material, may not be added to animal feed or pet food. About four million cows were killed during the eradication programme in the UK.
Four cases were reported globally in 2017, and the condition is considered to be nearly eradicated. In the United Kingdom, more than 184,000 cattle were diagnosed from 1986 to 2015, with the peak of new cases occurring in 1993. A few thousand additional cases have been reported in other regions of the world. In addition, it is believed that several million cattle with the condition likely entered the food supply during the outbreak.
Signs are not seen immediately in cattle, due to the disease's extremely long incubation period. Some cattle have been observed to have an abnormal gait, changes in behavior, tremors and hyper-responsiveness to certain stimuli. Hindlimb ataxia affects the animal's gait and occurs when muscle control is lost. This results in poor balance and coordination. Behavioural changes may include aggression, anxiety relating to certain situations, nervousness, frenzy and an overall change in temperament. Some rare but previously observed signs also include persistent pacing, rubbing and licking. Additionally, nonspecific signs have also been observed which include weight loss, decreased milk production, lameness, ear infections and teeth grinding due to pain. Some animals may show a combination of these signs, while others may only be observed demonstrating one of the many reported. Once clinical signs arise, they typically get worse over the subsequent weeks and months, eventually leading to recumbency (making the animal a downer), coma and death.
BSE is an infectious disease believed to be due to a misfolded protein, known as a prion. Cattle are believed to have been infected from being fed meat and bone meal that contained the remains of other cattle who spontaneously developed the disease or scrapie-infected sheep products. The outbreak increased throughout the United Kingdom due to the practice of feeding meat-and-bone meal to young calves of dairy cows.
BSE prions are misfolded forms of the particular brain protein called prion protein. When this protein is misfolded, the normal alpha-helical structure is converted into a beta sheet. The prion induces normally-folded proteins to take on the misfolded phenotype in an exponential cascade. These sheets form small chains which aggregate and cause cell death. Massive cell death forms lesions in the brain which lead to degeneration of physical and mental abilities and ultimately death. The prion is not destroyed even if the beef or material containing it is cooked or heat-treated under normal conditions and pressures. Transmission can occur when healthy animals come in contact with tainted tissues from others with the disease, generally when their food source contains tainted meat.
The British Government enquiry took the view that the cause was not scrapie, as had originally been postulated, but was some event in the 1970s that could not be identified.
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Bovine spongiform encephalopathy
Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is an incurable and always fatal neurodegenerative disease of cattle. Symptoms include abnormal behavior, trouble walking, and weight loss. Later in the course of the disease, the cow becomes unable to function normally. There is conflicting information about the time between infection and onset of symptoms. In 2002, the World Health Organization suggested it to be approximately four to five years. Time from onset of symptoms to death is generally weeks to months. Spread to humans is believed to result in variant Creutzfeldt–Jakob disease (vCJD) or Creutzfeldt–Jakob disease (CJD). As of 2024[update], a total of 233 cases of vCJD had been reported globally.
BSE is thought to occur due to an infection by a misfolded protein, known as a prion. Cattle are believed to have been infected by being fed meat-and-bone meal that contained either the remains of cattle who spontaneously developed the disease or scrapie-infected sheep products. The United Kingdom was afflicted with an outbreak of BSE and vCJD in the 1980s and 1990s. The outbreak increased throughout the UK due to the practice of feeding meat-and-bone meal to young calves of dairy cows. Cases are suspected based on symptoms and confirmed by examination of the brain. Cases are classified as classic or atypical, with the latter divided into H- and L types. It is a type of transmissible spongiform encephalopathy.
Efforts to prevent the disease in the UK include not allowing any animal older than 30 months to enter either the human food or animal feed supply. In continental Europe, cattle over 30 months must be tested if they are intended for human food. In North America, tissue of concern, known as specified risk material, may not be added to animal feed or pet food. About four million cows were killed during the eradication programme in the UK.
Four cases were reported globally in 2017, and the condition is considered to be nearly eradicated. In the United Kingdom, more than 184,000 cattle were diagnosed from 1986 to 2015, with the peak of new cases occurring in 1993. A few thousand additional cases have been reported in other regions of the world. In addition, it is believed that several million cattle with the condition likely entered the food supply during the outbreak.
Signs are not seen immediately in cattle, due to the disease's extremely long incubation period. Some cattle have been observed to have an abnormal gait, changes in behavior, tremors and hyper-responsiveness to certain stimuli. Hindlimb ataxia affects the animal's gait and occurs when muscle control is lost. This results in poor balance and coordination. Behavioural changes may include aggression, anxiety relating to certain situations, nervousness, frenzy and an overall change in temperament. Some rare but previously observed signs also include persistent pacing, rubbing and licking. Additionally, nonspecific signs have also been observed which include weight loss, decreased milk production, lameness, ear infections and teeth grinding due to pain. Some animals may show a combination of these signs, while others may only be observed demonstrating one of the many reported. Once clinical signs arise, they typically get worse over the subsequent weeks and months, eventually leading to recumbency (making the animal a downer), coma and death.
BSE is an infectious disease believed to be due to a misfolded protein, known as a prion. Cattle are believed to have been infected from being fed meat and bone meal that contained the remains of other cattle who spontaneously developed the disease or scrapie-infected sheep products. The outbreak increased throughout the United Kingdom due to the practice of feeding meat-and-bone meal to young calves of dairy cows.
BSE prions are misfolded forms of the particular brain protein called prion protein. When this protein is misfolded, the normal alpha-helical structure is converted into a beta sheet. The prion induces normally-folded proteins to take on the misfolded phenotype in an exponential cascade. These sheets form small chains which aggregate and cause cell death. Massive cell death forms lesions in the brain which lead to degeneration of physical and mental abilities and ultimately death. The prion is not destroyed even if the beef or material containing it is cooked or heat-treated under normal conditions and pressures. Transmission can occur when healthy animals come in contact with tainted tissues from others with the disease, generally when their food source contains tainted meat.
The British Government enquiry took the view that the cause was not scrapie, as had originally been postulated, but was some event in the 1970s that could not be identified.
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