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From: TSS ()
Subject: Japans 2 young cases of BSE amount of abnormal PrP very small
Date: May 16, 2007 at 11:39 am PST

BSE infection from young cattle to mice not confirmed

The Asahi Shimbun

Experiments on mice showed that mad cow disease in two cattle aged 21 and 23
months old was not contagious, a finding that could change attitudes about
food safety.

The results of the tests, contained in an interim report compiled by a
health ministry-commissioned research group, might lead to a conclusion that
humans can safely eat meat from cattle up to 23 months old, even if they
were infected with bovine spongiform encephalopathy (BSE), or mad cow

The latest finding could also influence Japan's conditions on beef imports
from the United States. Japan currently limits U.S. beef imports to cattle
20 months old or younger when slaughtered.

"If the infection cannot be confirmed through the experiments between mice,
then it would be difficult to verify the infectiousness (of BSE)," an expert

The research group, headed by Tetsutaro Sata, chief of the Department of
Pathology at the National Institute of Infectious Diseases, is now compiling
a detailed academic paper based on the findings.

The Ministry of Health, Labor and Welfare is also preparing to report the
study to the Cabinet Office's Food Safety Commission, according to sources.

The 23-month-old cow was born in October 2001 and processed at a plant in
Ibaraki Prefecture in October 2003, according to the researchers. The
21-month-old cow was born in January 2002 and processed in Hiroshima
Prefecture in November 2003.

Both cows were confirmed as infected with BSE when they were processed. It
is rare for cattle that young to have BSE.

Cattle are confirmed to be contaminated with BSE if an abnormal prion
protein, the substance that triggers the disease, is detected in the

The young cattle had only between 1/500 and 1/1000 of the amount of prion
protein found in other BSE-infected cows, so the research group conducted
experiments at the National Institute of Animal Health in Tsukuba, Ibaraki
Prefecture, to see if the prion protein was infectious.

The group injected fluid taken from the brains of the two cows into the
brains of mice that were genetically modified to make them more susceptible
to the disease.

Under ordinary circumstances, the mice would develop abnormalities in about
220 days.

But reports and other information obtained by The Asahi Shimbun showed that
five mice injected with the brain fluid of the 23-month-old cow survived 600
to 860 days. Six mice injected with the fluid from the 21-month-old cow
lived for 505 to 927 days.

Not one of the mice was confirmed as being infected with BSE.

The researchers also injected brain fluid from mice used in the earlier
experiments into the brains of other mice to double check the infectiousness
of the disease in the young cattle.

The second set of mice injected with brain fluid showed no signs of BSE
contamination after at least 495 days.

BSE is more easily passed on from mouse to mouse than from cow to mouse.

The first BSE-contaminated cow in the United States was confirmed in
December 2003, prompting Japan to ban U.S. beef imports.

In negotiations for the resumption of the imports, Washington called on
Tokyo to adopt international standards set by the World Organization for
Animal Health, which says boneless meat from cattle aged 30 months or
younger are safe.

But Japan argued that the restriction should be applied to cattle as young
as 20 months because of the two young cows confirmed with BSE in Japan. The
United States eventually accepted Japan's argument and reached an agreement.

"From the perspective of food safety, I think that the decision at the time
to declare the cows as infected with BSE and to exclude meat (from cattle
aged 20 months or older) from the market was not wrong," said Takashi
Yokoyama, chief of the Research Center for Prion Diseases at the National
Institute of Animal Health who was in charge of the experiments. "That
decision is totally unrelated to the latest experiments."

Still, Kiyotoshi Kaneko, professor of physiology at Tokyo Medical
University, said the results do not provide a 100-percent guarantee of the
safety of beef.

"I think that rather than saying that BSE was not infectious, it is more
appropriate to say that the amount of abnormal prion protein was very small,
and it did not effectively multiply in the mice," Kaneko said. "It is
reasonable to assume that there is not much of a risk to human health, but I
wonder how far we can generalize the results of the experiments to humans."
(IHT/Asahi: May 9,2007)

Public should have say
Atsushi Miyazaki / Yomiuri Shimbun Staff Writer

In its recent interim report on the two domestically raised cows that were diagnosed with bovine spongiform encephalopathy (BSE) in 2003, the health ministry's research team said it could not confirm the infectiousness of the two cows--23 months old and 21 months old--through animal experiments.

Blanket testing of domestic cattle started in 2001 after a BSE-infected cow was found for the first time in Japan. The range of inspection has been narrowed to those that are older than 21 months, but effective blanket testing continues.

So far, 32 head of cattle have been diagnosed with BSE, and most of them were aged 30 months or older. But the 2003 discovery of BSE in the 23-month-old and 21-month-old cows shocked experts and other concerned parties.

BSE, or mad cow disease, is caused by abnormal prions as they propagate gradually over a period of years in the brain of an infected cow. The amount of accumulated abnormal prions is small in the case of young cows, causing little chance for those who eat the meat of young cows to develop a variant of Creutzfeldt-Jakob disease. Therefore, cows aged 30 months or older are subject to BSE testing under international standards.

In past negotiations with the United States over beef imports, Japan consistently demanded that imported beef come from cows aged 20 months or younger. This was because of concerns over the infectiousness of the young domestic cows that were found to have BSE.

For this reason, the research team examined the infectiousness by injecting liquid extracted from the brains of the two cows into those of mice, but could not confirm the rate of infection after about 2-1/2 years of observation.

If the same results are reached in the team's final report to be compiled at the end of the current fiscal year, Japan may lose the ground for its assertion that imported beef should come from cows aged 20 months or younger.

The amount of abnormal prions in the two cows was one-500th or one-1,000th of that usually found in infected cows. So there has been suspicion about the infectiousness since the two cows were found to be infected with BSE.

The Paris-based World Organization for Animal Health (OIE) is likely to acknowledge the safety of U.S. beef to a certain extent and designate the United States as a country qualified to export its beef regardless of the age of the cows.

Based on OIE's expected judgment and the ministry team's research results, the United States is expected to strengthen its demand for Japan to ease its beef import restrictions. In this case, Japan will face increasing pressure to raise the age of cows subject to testing to the international standard.

But some experts point out that the ministry's interim research results do not necessarily rule out the danger posed by young cows infected with BSE. The team's chief researcher, Tetsutaro Sata, who manages the National Institute of Infectious Diseases Pathology Department, said, "The volume of abnormal prions in the brains of a mouse was less than what can be detected by the present technology, but there is a possibility of the volume increasing over time."

In fact, many aspects concerning prions have yet to be scientifically elucidated. Scientists still do not know how many abnormal prions need to enter the body to cause the infection. It also remains to be seen whether results from infection testing on mice can be applied to humans. The international standard in BSE testing must be followed, but it is equally important to continue research for scientific verification of risk judgments.

The progress of technology has made it possible to detect amounts as small as a trillionth of a gram of hazardous chemical substances such as agrochemicals. Technological advances reveal new risks. If a slight amount of abnormal prions is detected in a young cow that was earlier judged to have almost no BSE infection, it is necessary to scrupulously weigh the risks and benefits to be had by admitting beef imports.

Prof. Tadashi Kobayashi of the Osaka University Center for the Study of Communication-Design said, "When science exposes a low risk, it should be society--not scientists--that judges whether to accept it."

Behind the continued blanket testing of cows is consumers' lingering anxiety over the safety of beef. In this sense, it becomes even more important for the government--as part of its risk management--to promote so-called risk communication with the people by telling them precise information about the scientific risk.

The Food Safety Commission, which has looked into the safety risks of U.S. beef, will discuss this matter shortly. In a commission meeting on May 10, participants expressed strong dissatisfaction with the government for a delay in disclosing the research results. One of them said, "We have not received any report on the research results [from the government], even though we've been calling for public disclosure for 1-1/2 years."

Risk communication is premised on telling the people precisely what has or has not been scientifically elucidated. Scientific conclusions should not be treated as a "final endorsement of safety." Constant efforts must be made to publicize the results of scientific efforts.

(May. 17, 2007)


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