Market Farming

[Sojourner <sojournr AT missouri.org>]

Shelley Pasco wrote:
> 
> Liz, I think what scares me more about these products are the unknowns. I
> remember hearing that no one could be sure that steaming or baking bone meal
> would render the mad-cow prions inactive.

Dry heat will not destroy the prion.  Steam will destroy most but not
all of the prion.  Pressurized steam at the correct pressure/temp will
destroy the prion.

> There's just no way to know
> because it can have an incubation period of up to 20 years.

Twenty years is excessive.  The incubation period is 3 to 9 years.

> Who's been
> testing that?

The World Health Organization and any number of other organizations and
research facilities.  WHO tests worldwide for BSE (bovine spongiform
encephalopathy) as well for a number of other pathogens as part of a
world-wide epidemiology watch.

> Sojourner said that there haven't been any cases found
> here (YET). There may be animals or people running around
> with the prions in their systems, just waiting to become
> active.

Highly unlikely.  There has never been any evidence of the prion or the
disease in 15 years, 5 times the minimum incubation period and nearly
double the max.  There has been more than enough time for BSE to appear
in this country.

> The thing is, I'm not certain enough that it's safe. I
> don't want to absorb these things.

In order to be infected you must

1) ingest a significant amount of infected meat or other material, or
receive an injection of say a growth hormone from infected cattle. 
There are several such substances but they are rare and I don't remember
other than the growth hormone what they are.

For obvious reasons we have no statistical data on how much infected
material one must eat to have x percent risk of contracting BSE, but its
a lot.  Much more than you would get handling bone meal, even assuming
it were infected (and there has never been any infected material found
in this country, they even chased down about 500 cows that had been
imported from Britain and tested for BSE in those cows and the other
cattle they had been around and none was ever found).

Injected material (like the growth hormones), on the other hand, carries
a much much higher risk with much smaller quantities, again, assuming it
actually contains infectious material.

Only neural tissue has been found to be infectious, so even if a cow is
infected, the meat must be contaminated by neural tissue (brain, spinal
column, retinal tissue) to contain any infectious material.  This
lessens risk of exposure even more.

2) The prion must survive the species barrier - it is difficult for
non-human TSEs (Transmittable Spongiform Encephalopathies) to infect
humans.  They had great difficulty infecting mice with BSE under near
perfect laboratory conditions.  It can be done, and it can happen, but
its highly unlikely.  Even in Britain, during the period when BSE was
epidemic among cattle, fewer than 20 people came down with vCJD, which
is now believed to be linked to BSE.  This was during the time period
when estimates ranging from 3% to as high as 5% of retail beef may have
come from infected cattle.

3) You have to be genetically susceptible to CJD (Cruetzfeldt-Jakob's
disease, a human TSE which BSE mimics in humans).  There is a genetic
marker for this in humans, I forget which codon its on, but if you're
really really interested I'm sure I could dig it up.

It's very, very hard for a human to contract BSE even when exposed to
infected materials.  Your chances of getting killed in an auto accident
are much much higher.

Life cannot be made risk free.  I hate to bring it up again, but there's
always the possibility there's a meteorite out there with your name on
it.  <VBG>

I'm not trying to belittle your fears, but in all honesty you are
worrying about something that your risk of ever being exposed to, let
alone actually managing to contract it, is so vanishingly small as to be
negligible.  You're far more likely to be struck by lightning.

> I wouldn't mind composting offal from my own animals that
> have been fed only vegetable proteins, but not if they've
> been fed animal products.

Its certainly reasonable to take ordinary precautions, and I share your
distaste for the way feedlot cattle are fed (and poultry as well). 
There are a lot of good reasons to avoid agbiz factory meats; that's why
I'm planning on raising my own.  But in all honesty, fear of contracting
BSE is not one of them.

-- 
Holly ;-D
Contrary Peasant
sojournr AT missouri.org