FACT SHEET # 2 Bovine Spongiform Encephalopathy (BSE)
FACT SHEET # 2 BOVINE SPONGIFORM ENCEPHALOPATHY (BSE)
(Adapted from Animal and Plant Health Inspection Service)
Bovine spongiform encephalopathy (BSE), also known as "mad cow disease," is a chronic, degenerative disease affecting the central nervous system of cattle. Worldwide, there have been more than 178,000 cases since the disease was first diagnosed in 1986 in Great Britain. The disease has also been confirmed in native-born cattle in Belgium, Denmark, France, Germany, Ireland, Italy, Luxembourg, Liechtenstein, the Netherlands, Northern Ireland, Portugal, Spain and Switzerland. It has also been diagnosed in cattle exported from Great Britain to Oman, the Falkland Islands, Germany, Denmark, Canada, Italy, and the Azores. However, over 95% of all BSE cases have occurred in the United Kingdom.
BSE is not known to exist in the United States.
No cases of BSE have been confirmed in the USA despite 10 years of active surveillance. BSE belongs to the family of diseases known as transmissible spongiform encephalopathies (TSE's). A transmissible agent, which is yet to be fully characterized, causes these diseases. TSE's share the following common characteristics:
a. a prolonged incubation period of months or years;
b. a progressive debilitating neurological illness which is always fatal;
c. pathological changes appear to be confined to the central nervous system (CNS).
d. the transmissible agent elicits no detectable specific immune response in the host that has inhibited the development of a live animal diagnostic test.
Clinical Signs of BSE in Cattle
Affected animals may display changes in temperament, such as nervousness or aggression; abnormal posture; incoordination and difficulty in rising; decreased milk production; or loss of body condition despite continued appetite. There is no treatment, and affected cattle die. The incubation period ranges from 2 to 8 years. Following the onset of clinical signs, the animal's condition deteriorates until it dies or is destroyed. This usually takes from 2 weeks to 6 months. Most cases in Great Britain have occurred in dairy cows between 3 and 6 years of age.
Causative Agent of BSE
The causative agent of BSE as well as other TSE's is yet to be fully characterized. Three main theories on the nature of the agent have been proposed:
· An unconventional virus.
· A prion or abnormal protein, capable of causing a cell to produce more abnormal protein.
· A virino or "incomplete" virus.
The BSE agent (1) is smaller than most viral particles and is highly resistant to heat, ultraviolet light, ionizing radiation, and common disinfectants that normally inactivate viruses or bacteria; (2) causes no detectable immune or inflammatory response in the host; and (3) has not been observed microscopically.
How BSE is Currently Diagnosed
There is no test to detect the disease in a live animal. Microscopic examination of the brain is the primary laboratory method used to confirm a diagnosis of BSE. There are also several techniques used to detect the prion (PrPres) protein.
Have other Animal TSE's been found in the US?
TSE's HAVE been found in the United States: Scrapie in sheep and goats, transmissible mink encephalopathy, and chronic wasting disease of deer and elk.
Cause of BSE in Great Britain
BSE in Great Britain is believed to have been caused by animal feed containing contaminated meat and bone meal. The causative agent is suspected to be from either scrapie-affected sheep or cattle with a previously unidentified TSE. Changes in rendering practices in the early 1980's may have potentiated the agent's survival in meat and bone meal.
Outcome of the one Case in Canada
There have been NO cases of BSE in native cattle in North America. The one case of BSE in a single cow in Canada imported from Great Britain has been dealt with by destroying the affected cow and all its herd mates, as well as other cattle determined to be a risk by animal health officials in Canada.
Transmission of BSE
There is no evidence that BSE spreads horizontally, i.e., by contact between unrelated adult cattle or from cattle to other species. Some evidence suggests that maternal transmission may occur at an extremely low level. Results of British research show that there is approximately a 9-percent increase in the occurrence of BSE in offspring of BSE-affected dams as compared to calves born to dams where BSE was not detected. The study did not ascertain if this was the result of genetic factors of true transmission. The research did however point out that at this level if maternal transmission does occur it alone will not sustain the epidemic.
BSE
The UK's Spongiform Encephalopathy Advisory Committeee (SEAC) concluded that although there was no direct scientific evidence of a link between BSE and variant Creutzfeldt-Jakob Disease (vCJD), based on current data and in the absence of any credible alternative, the most likely explanation was that the cases were linked to exposure to BSE. Subsequent research with mice provided evidence that BSE and vCJD have the same signature or are the same "strain."
USDA Actions
The USDA policy has been to be proactive. APHIS has taken measures in surveillance, prevention, education, and response. Import restrictions have been in place since 1989, and active surveillance efforts began in 1990. The USDA continually monitors and assesses all ongoing events and research findings regarding spongiform encephalopathies, as new information and knowledge may lead to revised conclusions and prevention measures. APHIS has also created a Transmissible Spongiform Encephalopathy (TSE) Working Group to analyze risks of BSE to the United States, disseminate accurate information about TSE's, and act as a reference source for responding to questions about TSE's.
APHIS has actively shared information and met with State and Federal agencies, including the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the Food Safety and Inspection Service (FSIS), the National Institute of Health (NIH), and stakeholders to assure proper actions are taken in response to changing knowledge and information concerning BSE. BSE is a reportable disease by accredited veterinarians.
What types of BSE surveillance is being done?
USDA-APHIS, in cooperation with USDA-FSIS and State diagnostic laboratories, has a comprehensive surveillance program.
· APHIS educates veterinary practitioners, veterinary laboratory diagnosticians, industry and producers on clinical signs and pathology of BSE.
· APHIS monitors the remaining cattle imported from the United Kingdom.
Between 1981 and 1989, 496 cattle were imported from the United Kingdom and the Republic of Ireland. These U.K. imports have been traced, and there were only 4 cattle alive in the United States as of February 1999. All of these animals have been under quarantine since April 1996. In July 1989, the importation of live ruminants from the United Kingdom was banned.
In addition, 2 head of cattle imported from Belgium in 1996 are under quarantine. APHIS, in cooperation with the States and industry, continues to purchase these animals for diagnostic purposes. No evidence of BSE has been found in any of these imported animals.
Does the United State permit the feeding of ruminant protein to ruminants?
On August 4, 1997, the Food and Drug Administration (FDA) prohibited the feeding of most mammalian proteins to ruminants.
What proactive initiatives are underway to educate farmers, veterinarians, extension agents, etc.?
An important part of the USDA's active surveillance program is in the training of veterinary practitioners in the clinical signs, diagnosis and sample submission for BSE. Over 250 Federal and State veterinarians throughout the U.S. have been trained in the recognition of Foreign Animal Diseases (FAD's) including BSE. Videotapes of cattle showing clinical signs of BSE have been distributed to veterinarians in Federal and State governments, veterinary diagnostic laboratories, and pathology departments of veterinary colleges. In addition, APHIS personnel have given numerous presentations to various animal health groups.
What measures has USDA-APHIS taken to prevent the introduction of BSE?
To prevent BSE from entering the United States, APHIS restricted the importation of live ruminants and certain ruminant products form countries where BSE is known to exist as of July 21, 1989.
Certain products (serum, glands, collagen, etc. to be used in cosmetics) cannot be imported into the United States, except under special permit for scientific, educational or research purposes. Importation requests for ruminant material are considered individually, and authorization is granted only to those materials that would not allow exposure to ruminants in the United States.
Has the importation of cattle semen and embryos from BSE-affected countries been allowed?
Yes. No BSE infectivity has been detected in embryos, semen, or reproductive tissues of BSE-affected cows and bulls. Embryo transfer experiments are underway in cattle and all interim results are negative, thus far. However, due to the inconclusive findings of the maternal transmission study on BSE and two studies, which found sheep scrapie to be transmitted via embryo transfer, the importation of embryos from BSE-affected and high-risk countries has been suspended.
What actions are taken at USDA-inspected slaughter establishments to ensure that cattle with BSE would not enter the human food supply?
All cattle presented for slaughter in the United States are inspected before slaughter by FSIS for signs of central nervous system impairment. Any animals exhibiting neurologic signs during this inspection are condemned, and the meat is not permitted for use as human food. The brains from these animals are submitted to USDA's National Veterinary Services Laboratories for analysis.
Does USDA have a response plan in the event a case of BSE or TSE is diagnosed in U.S. cattle?
In 1990, APHIS developed a plan to respond to a confirmation of BSE in the U.S. In August 1996, a joint APHIS-FSIS working group updated this BSE response plan. The purpose of the plan is to provide a step-by-step plan of action in the event that a case of BSE is detected in the United States. The plan outlines those events that should take place, including identification of a suspect animal, confirmation, the Epidemiologic investigation, animal and herd disposition activities, and communication of information.
(Adapted from Animal and Plant Health Inspection Service)
Bovine spongiform encephalopathy (BSE), also known as "mad cow disease," is a chronic, degenerative disease affecting the central nervous system of cattle. Worldwide, there have been more than 178,000 cases since the disease was first diagnosed in 1986 in Great Britain. The disease has also been confirmed in native-born cattle in Belgium, Denmark, France, Germany, Ireland, Italy, Luxembourg, Liechtenstein, the Netherlands, Northern Ireland, Portugal, Spain and Switzerland. It has also been diagnosed in cattle exported from Great Britain to Oman, the Falkland Islands, Germany, Denmark, Canada, Italy, and the Azores. However, over 95% of all BSE cases have occurred in the United Kingdom.
BSE is not known to exist in the United States.
No cases of BSE have been confirmed in the USA despite 10 years of active surveillance. BSE belongs to the family of diseases known as transmissible spongiform encephalopathies (TSE's). A transmissible agent, which is yet to be fully characterized, causes these diseases. TSE's share the following common characteristics:
a. a prolonged incubation period of months or years;
b. a progressive debilitating neurological illness which is always fatal;
c. pathological changes appear to be confined to the central nervous system (CNS).
d. the transmissible agent elicits no detectable specific immune response in the host that has inhibited the development of a live animal diagnostic test.
Clinical Signs of BSE in Cattle
Affected animals may display changes in temperament, such as nervousness or aggression; abnormal posture; incoordination and difficulty in rising; decreased milk production; or loss of body condition despite continued appetite. There is no treatment, and affected cattle die. The incubation period ranges from 2 to 8 years. Following the onset of clinical signs, the animal's condition deteriorates until it dies or is destroyed. This usually takes from 2 weeks to 6 months. Most cases in Great Britain have occurred in dairy cows between 3 and 6 years of age.
Causative Agent of BSE
The causative agent of BSE as well as other TSE's is yet to be fully characterized. Three main theories on the nature of the agent have been proposed:
· An unconventional virus.
· A prion or abnormal protein, capable of causing a cell to produce more abnormal protein.
· A virino or "incomplete" virus.
The BSE agent (1) is smaller than most viral particles and is highly resistant to heat, ultraviolet light, ionizing radiation, and common disinfectants that normally inactivate viruses or bacteria; (2) causes no detectable immune or inflammatory response in the host; and (3) has not been observed microscopically.
How BSE is Currently Diagnosed
There is no test to detect the disease in a live animal. Microscopic examination of the brain is the primary laboratory method used to confirm a diagnosis of BSE. There are also several techniques used to detect the prion (PrPres) protein.
Have other Animal TSE's been found in the US?
TSE's HAVE been found in the United States: Scrapie in sheep and goats, transmissible mink encephalopathy, and chronic wasting disease of deer and elk.
Cause of BSE in Great Britain
BSE in Great Britain is believed to have been caused by animal feed containing contaminated meat and bone meal. The causative agent is suspected to be from either scrapie-affected sheep or cattle with a previously unidentified TSE. Changes in rendering practices in the early 1980's may have potentiated the agent's survival in meat and bone meal.
Outcome of the one Case in Canada
There have been NO cases of BSE in native cattle in North America. The one case of BSE in a single cow in Canada imported from Great Britain has been dealt with by destroying the affected cow and all its herd mates, as well as other cattle determined to be a risk by animal health officials in Canada.
Transmission of BSE
There is no evidence that BSE spreads horizontally, i.e., by contact between unrelated adult cattle or from cattle to other species. Some evidence suggests that maternal transmission may occur at an extremely low level. Results of British research show that there is approximately a 9-percent increase in the occurrence of BSE in offspring of BSE-affected dams as compared to calves born to dams where BSE was not detected. The study did not ascertain if this was the result of genetic factors of true transmission. The research did however point out that at this level if maternal transmission does occur it alone will not sustain the epidemic.
BSE
The UK's Spongiform Encephalopathy Advisory Committeee (SEAC) concluded that although there was no direct scientific evidence of a link between BSE and variant Creutzfeldt-Jakob Disease (vCJD), based on current data and in the absence of any credible alternative, the most likely explanation was that the cases were linked to exposure to BSE. Subsequent research with mice provided evidence that BSE and vCJD have the same signature or are the same "strain."
USDA Actions
The USDA policy has been to be proactive. APHIS has taken measures in surveillance, prevention, education, and response. Import restrictions have been in place since 1989, and active surveillance efforts began in 1990. The USDA continually monitors and assesses all ongoing events and research findings regarding spongiform encephalopathies, as new information and knowledge may lead to revised conclusions and prevention measures. APHIS has also created a Transmissible Spongiform Encephalopathy (TSE) Working Group to analyze risks of BSE to the United States, disseminate accurate information about TSE's, and act as a reference source for responding to questions about TSE's.
APHIS has actively shared information and met with State and Federal agencies, including the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the Food Safety and Inspection Service (FSIS), the National Institute of Health (NIH), and stakeholders to assure proper actions are taken in response to changing knowledge and information concerning BSE. BSE is a reportable disease by accredited veterinarians.
What types of BSE surveillance is being done?
USDA-APHIS, in cooperation with USDA-FSIS and State diagnostic laboratories, has a comprehensive surveillance program.
· APHIS educates veterinary practitioners, veterinary laboratory diagnosticians, industry and producers on clinical signs and pathology of BSE.
· APHIS monitors the remaining cattle imported from the United Kingdom.
Between 1981 and 1989, 496 cattle were imported from the United Kingdom and the Republic of Ireland. These U.K. imports have been traced, and there were only 4 cattle alive in the United States as of February 1999. All of these animals have been under quarantine since April 1996. In July 1989, the importation of live ruminants from the United Kingdom was banned.
In addition, 2 head of cattle imported from Belgium in 1996 are under quarantine. APHIS, in cooperation with the States and industry, continues to purchase these animals for diagnostic purposes. No evidence of BSE has been found in any of these imported animals.
Does the United State permit the feeding of ruminant protein to ruminants?
On August 4, 1997, the Food and Drug Administration (FDA) prohibited the feeding of most mammalian proteins to ruminants.
What proactive initiatives are underway to educate farmers, veterinarians, extension agents, etc.?
An important part of the USDA's active surveillance program is in the training of veterinary practitioners in the clinical signs, diagnosis and sample submission for BSE. Over 250 Federal and State veterinarians throughout the U.S. have been trained in the recognition of Foreign Animal Diseases (FAD's) including BSE. Videotapes of cattle showing clinical signs of BSE have been distributed to veterinarians in Federal and State governments, veterinary diagnostic laboratories, and pathology departments of veterinary colleges. In addition, APHIS personnel have given numerous presentations to various animal health groups.
What measures has USDA-APHIS taken to prevent the introduction of BSE?
To prevent BSE from entering the United States, APHIS restricted the importation of live ruminants and certain ruminant products form countries where BSE is known to exist as of July 21, 1989.
Certain products (serum, glands, collagen, etc. to be used in cosmetics) cannot be imported into the United States, except under special permit for scientific, educational or research purposes. Importation requests for ruminant material are considered individually, and authorization is granted only to those materials that would not allow exposure to ruminants in the United States.
Has the importation of cattle semen and embryos from BSE-affected countries been allowed?
Yes. No BSE infectivity has been detected in embryos, semen, or reproductive tissues of BSE-affected cows and bulls. Embryo transfer experiments are underway in cattle and all interim results are negative, thus far. However, due to the inconclusive findings of the maternal transmission study on BSE and two studies, which found sheep scrapie to be transmitted via embryo transfer, the importation of embryos from BSE-affected and high-risk countries has been suspended.
What actions are taken at USDA-inspected slaughter establishments to ensure that cattle with BSE would not enter the human food supply?
All cattle presented for slaughter in the United States are inspected before slaughter by FSIS for signs of central nervous system impairment. Any animals exhibiting neurologic signs during this inspection are condemned, and the meat is not permitted for use as human food. The brains from these animals are submitted to USDA's National Veterinary Services Laboratories for analysis.
Does USDA have a response plan in the event a case of BSE or TSE is diagnosed in U.S. cattle?
In 1990, APHIS developed a plan to respond to a confirmation of BSE in the U.S. In August 1996, a joint APHIS-FSIS working group updated this BSE response plan. The purpose of the plan is to provide a step-by-step plan of action in the event that a case of BSE is detected in the United States. The plan outlines those events that should take place, including identification of a suspect animal, confirmation, the Epidemiologic investigation, animal and herd disposition activities, and communication of information.