SALEM, Ohio – Canadian agricultural officials continue to track possible sources of last week’s confirmed case of bovine spongiform encephalopathy, or BSE, in a 6-year-old beef cow in Fairview, Alberta.
The test that returned positive was taken Jan. 31. The emaciated cow had been condemned for suspected pneumonia, prior to slaughter, following routine surveillance.
Testing delay. It wasn’t until two weeks ago that the head was tested for BSE. One of the still-unanswered questions is why it took more than three months for the additional testing to take place.
Preliminary tests at a provincial laboratory and at Canada’s National Centre for Foreign Animal Disease couldn’t rule out BSE, so samples were sent to the World Reference Laboratory in Webridge, United Kingdom. The lab there verified the presence of BSE.
Only one case so far. The Canadian Food Inspection Agency immediately quarantined the farm and the remaining 191 head of cattle were killed and tested. Rapid diagnostic tests have all come back negative for BSE.
Cow owner Marwyn Peaster moved to Canada from Mississippi. Last Thursday, Peaster told Canadian media he bought the cow and 69 others in August 2002.
Two other farms where the cow was housed prior to joining Peaster’s herd were immediately quarantined. The animals were killed and removed for testing May 24-25.
As of Tuesday, May 27, Canada had placed 17 cattle herds under quarantine in Alberta, Saskatchewan and British Columbia.
The herds are being investigated related to the infected cow’s movement and the movement of her offspring. The three British Columbia farms are being investigated for feeding practices that may not have followed the feed ban.
The mother of the infected animal has been identified and was killed and also tested for BSE.
To date, more than 400 head of cattle have been destroyed.
“The clinical signs of BSE can sometimes be very subtle in the early stages,” said Lisa Ferguson, senior staff scientist at the USDA’s Animal and Plant Health Inspection Service in a teleconference May 22.
The incubation period ranges from two to eight years.
The USDA could not say whether any offspring came into the United States or whether any of the cow’s herdmates came from the United States.
U.S. actions. After being notified by Canada May 20, the United States immediately closed its borders to imports of ruminants or ruminant products, which includes cattle, sheep and goats, from Canada.
The USDA also immediately sent a technical team to Canada to assist the investigation.
Canada is the United States’ largest live cattle supplier and its second largest processed beef supplier. Approximately 1.7 million head of U.S. cattle imports in 2002 came from Canada, according to the USDA.
Approximately 60,000 dairy replacements move from Canada into the United States each year.
There has never been a recorded case of BSE in the United States.
Cause. Bovine spongiform encephalopathy, also called “mad cow disease,” is a chronic, degenerative disease affecting the central nervous system of cattle.
The BSE agent is found in the central nervous system tissue such as the brain or spinal cord; it is not found in meat.
The disease, which is not contagious, is caused by abnormal proteins called prions, according to Penn State veterinarian Larry Hutchinson.
These prions are thought to be transmitted through feed containing rendered byproducts of infected animals.
The United States has banned the use of animal protein in animal feed since 1997 and the USDA routinely tests feed samples to determine compliance. Last year, the department tested 600 domestic and 600 import feed samples.
USDA officials said last week tracing the infected cow’s feed for the last six years will be difficult.
Since 1989, the United States has also banned imports of cattle and cattle products from countries where BSE is known to exist.
Transmission of BSE. There is no evidence that BSE spreads through contact between unrelated adult cattle of from cattle to other species.
Some evidence suggests that maternal transmission may occur at an extremely low level.
Safeguards. There is no test to diagnose BSE in live animals. Diagnosis can only be confirmed by examining an animal’s brain after its death.
All live U.S. cattle are inspected by a veterinarian before going to slaughter. If an animal shows signs of a neurological disorder, it doesn’t enter the food chain and is tested for BSE.
Samples are sent overnight to a federal lab, where the average turn-around time for the test is eight days.
The United States has had an active federal BSE surveillance program since 1990. Nationally, USDA tested 19,990 cattle for BSE in fiscal year 2002.
As part of that surveillance program, for example, the Ohio Department of Agriculture sent 451 brain tissue samples to the federal lab in Ames, Iowa, in 2002. So far in federal fiscal year 2003, Ohio has sent 300 samples. The samples are collected by both state and federal inspectors, said Ohio Director of Agriculture Fred Dailey.
“We believe our surveillance is done at a level that we would find a one in a million case in the United States, if it was here,” said USDA’s Lisa Ferguson.
No cattle have ever been diagnosed with BSE in the United States.
Worldwide problem. Since 1986, approximately 187,000 cases of BSE have occurred among nearly 34,000 herds, mostly in the United Kingdom.
The UK epidemic peaked in 1993, with nearly 1,000 new cases reported weekly.
About two-thirds of those cases were in dairy herds.
The diseases has been confirmed in numerous other countries, including Japan, Israel, Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Italy, the Netherlands, Portugal, Spain and Switzerland.
Related diseases. BSE belongs to a family of diseases known as transmissible spongiform encephalopathies (TSEs).
This family includes a number of other animal diseases including scrapie in sheep, chronic wasting disease in deer and elk, and transmissible mink encephalopathy.
BSE has also been linked to similar human diseases, including a variant of Creutzfeldt-Jakob disease.
Get the details:
National Cattlemen’s Beef Association
Food and Drug Administration
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