Fwd: BSE crosses the Atlantic

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" grasshopper "

Mon, 22 Dec 2003 03:58:30 -0000

BSE crosses the Atlantic

 

 

BSE crosses the Atlantic

 

New Scientist vol 178 issue 2397 - 31 May 2003, page 6

 

 

The US and Canada were warned that some of their cattle might have

mad cow disease. But neither country has been testing enough animals

to rule this out

 

 

THE discovery of a BSE-infected cow in Canada confirms warnings from

European scientists three years ago that cattle in North America

could be infected. And if Canadian cattle are infected it is likely

that the disease is also present in the US.

 

The US and Canada test so few animals that low levels of BSE

infection would not be detected. Indeed, the number Canada tests

would be unlikely to reveal a level of infection any lower than what

the UK now has. Other countries have found many more cases after

increasing testing when the first infected cattle were reported.

 

What's more, neither country has taken any of the measures needed to

prevent people being infected by meat from diseased cattle

(see " What to do now " ). Even if people are eating infected meat,

there are unlikely to be many cases of vCJD, the human disease

linked to BSE. In the UK, the country worst hit by the disease, it

is thought unlikely that there will be more than 200 vCJD cases in

total. But BSE could still have a huge economic impact on the

massive $400 billion North American beef industry.

 

The Canadian case was an eight-year-old Black Angus beef cow in the

western province of Alberta. The province tests a sample of " high-

risk " cattle: those found dead or disabled on farms, or with

neurological symptoms, or that have been rejected by the abattoir.

Such animals are up to 10 times as likely as other animals to have

undetected BSE, so they are ideal for monitoring purposes.

 

This cow was rejected by an abattoir late in January because it had

pneumonia. The result was not announced until 20 May due to delays

caused by a backlog in testing, the 10 days it takes to do the test

that Canada uses, and the need to confirm the finding at the world

BSE reference laboratory at Weybridge in England.

 

Unlike Canada's only previous case, diagnosed in 1993 in a cow born

in Britain in 1987, this animal was born in Canada and must have

been infected there, probably by eating contaminated feed eight

years ago. Canada's Agriculture minister Lyle Vanclief insists it is

an " isolated case " . But cases of BSE don't happen spontaneously, and

other cattle would have eaten the same feed. " There must be more

cases, " says Marcus Doherr of the University of Bern in Switzerland,

a leading expert on BSE epidemiology. " For every case we detect, we

estimate there were three to five animals exposed. "

 

Europe has been urging North Americans to do more testing, Doherr

says. In 2000, he and other scientists working for the European

Commission concluded that BSE could be circulating at low levels in

the US and Canada, because British cattle imported before 1990 were

recycled as feed (New Scientist, 10 June 2000, p 4). The risk would

have peaked between 1993 and 1997. The Alberta cow was born in 1995.

 

But North America has been slow to test for BSE and does not use the

fast tests developed in Europe. This is partly because these tests

tend to produce false positives, which could be a headache in a

country that claims to be BSE-free.

 

In Alberta, which has 2.5 million cattle over 18 months old, the

target group for testing, only 1655 animals have been tested for BSE

since 1996 - half of them last year. Because so few animals are

being tested, infected cattle could go undetected. The 849 high-risk

cattle Alberta tested last year would only have been enough to

reliably detect a prevalence of infection in the high-risk group of

0.035 per cent, slightly more than the current rate in the UK. Of

course, there is a big margin of error: the true prevalence could be

lower or higher.

 

The situation is slightly better in the US, where nearly 20,000

cattle found dead on farms were tested for BSE last year. All were

negative. But the sample is still far too small to rule out the

existence of BSE in the US herd.

 

And until the US border was closed to Canadian beef last week, the

two countries' cattle industries were closely integrated. Last year,

Alberta shipped over half a million live cattle to the US. They also

trade large volumes of meat and bonemeal for feeding to animals -

the main way BSE is transmitted.

 

 

What to do now

 

The US and Canada should use the rapid tests developed in Europe to

test as many sick and dead animals as possible. Some apparently

healthy animals should also be tested at slaughter to ensure that

farmers do not stop sending sick animals to the slaughterhouse for

fear BSE will be discovered on their farms.

 

The US should drop the $75 fee it charges farmers who bring reject

animals for rendering. This encourages farmers to quietly bury them,

so they cannot be tested.

 

If BSE is found:

 

Ban all ruminants (cattle and sheep) being turned into meat and bone

meal (MBM) for feeding to animals. The US and Canada still allow

ruminants to be fed to non-ruminants, and vice versa. But Europe's

experience suggests this consistently leads to ruminants eating

ruminants, because of accidental contamination in feed mills,

failure to follow the rules and farmers feeding, say, pig feed to

cows to avoid waste.

 

Better still, completely ban the use of MBM, as Europe did when it

discovered that it was too complicated to ban some feeds for some

animals. Both the US and Canada insist they already have adequate

procedures in place, but a US General Accounting Office report last

year found many feed companies aren't following the rules.

 

Remove from food the parts of cattle most likely to transmit the

disease to people, including the brain, spinal cord and spleen.

 

Ban mechanical separators for extracting meat from the spinal cord

for hot dogs and sausages.

 

Stop abbatoirs using stun guns that can scatter brain tissue onto

parts of the animal eaten by people (the US is considering this).

 

 

 

 

 

 

Debora MacKenzie

 

 

 

 

 

 

 

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