12th case of mad cow confirmed in Japan

[PaulTB]

It is interesting to see that amomg the cases of BSE found in Japan (first 4 listed in Paul's link), the cows were all over 5 years old.

All 12 or the first 4 listed in my link?

That seems to confirm that it is difficult to detect the disease among younger cows,

Not really. You could equally take it that cows were more likely to have been exposed further back. It is correct that tests can be are less reliable when the cows haven't had time for the disease to progress for long but just exactly how much that is true depends on which tests are being talked about.

during the incubation period. This is what scares me the most when I hear the authorities saying that "it is safe because the test were negative" (obvious nonsense).

It's 'safe' (on a purely statistical basis) because vCJD turned out to be far less easy to get than feared. The long (and unknown) period before it takes effect made it a great scare target but it now seems fairly clearly to have peaked in the country where the problem first surfaced.

http://www.cjd.ed.ac.uk/figures.htm

A country where Mad Cow disease was, and is, much more rampant that it is now in Japan - however poor the tests.

http://www.defra.gov.uk/animalh/bse/.../overview.html

Oh and this link
http://ije.oupjournals.org/cgi/conte...tract/32/5/784
suggests that the best fit for incubation period is 11 years. With the peak BSE cases in the UK occurring at 1992/1993
http://www.defra.gov.uk/animalh/bse/...aphs/repts.pdf
this would be consistent with peak vCJD cases in 2003/2004.