- Hello Jeff and Patricia,
-
- I hope you don't mind me butting in again, but I see
- you are also worried about TSEs and the Environment,
- and rightly so. I have done research on this for the
- past few years, so I wish to share this data with you.
-
- Your story:
-
- Admission Of Possible CWD/BSE Contaminated Ground
-
- From Patricia Doyle, PhD
- http://www.rense.com/general33/contam.htm
-
- Now, please let me add my 2 cents worth of support to
- this...
-
- CWD/TSEs & ENVIRONMENT CONTAMINATION
-
- I believe it to be very irresponsible to dispose
- of clinical/sub-clinial cases of CWD or any animal
- with TSEs in landfills...
-
- TSS
-
- Aguzzi warns of CWD danger
-
- The TSE family of diseases also includes chronic wasting
disease (CWD)
- in deer, a condition that has spread in the US in recent
years (Nature
- 416, 569; 2002). Speaking at the Days of Molecular Medicine
conference
- in La Jolla in March, prion expert Adriano Aguzzi issued
a strong
- warning against underestimating this form of TSE.
-
- "For more than a decade, the US has by-and-large
considered mad cows
- to be an exquisitely European problem. The perceived
need to protect
- US citizens from this alien threat has even prompted
the deferral of
- blood donors from Europe," he said. "Yet the
threat-from-within
- posed by CWD needs careful consideration, since the evidence
that CWD
- is less dangerous to humans than BSE is less-than-complete.
Aguzzi
- went on to point out that CWD is arguably the most mysterious
of all
- prion diseases.
-
- "Its horizontal spread among the wild population
is exceedingly
- efficient, and appears to have reached a prevalence unprecedented
even
- by BSE in the UK at its peak. The pathogenesis of CWD,
therefore,
- deserves a vigorous research effort. Europeans also need
to think
- about this problem, and it would be timely and appropriate
to increase
- CWD surveillance in Europe too." Aguzzi has secured
funding from the
- National Institutes of Health to investigate CWD, and
the effort will
- be lead by Christina Sigurdson in his department at the
University of
- Zurich. KAREN BIRMINGHAM, LONDON
-
- This quote from Dr. Gambetti is especially significant
since he is the
- rather cautious TSE researcher under contract with the
Centers for Disease
- Control to examine the brains of individuals who have
died of CJD.
- -----------------
-
- Pierluigi Gambetti, director of the National Prion Disease
Pathology
- Surveillance Center at Case Western Reserve University
in Cleveland,
- said all deer should be tested for chronic wasting disease
before any
- processing is done.
-
- "There is no way around it," he said. "Nobody
should touch that meat
- unless it has been tested."
-
- http://www.ledger-enquirer.com/mld/...ion/3954298.htm
-
-
- TSEs And The Environment
-
- The LANCET
- Volume 351, Number 9110 18 April 1998
-
- BSE: the final resting place
-
- How to dispose of dangerous waste is a question that
has vexed the human
- race for hundreds of years. The answer has usually been
to get it out of
- sight--burn it or bury it. In Periclean Athens, victims
of the plague
- were incinerated in funeral pyres; in 14th century Venice,
a law
- stipulated that Black Death corpses should be buried
to a minimum depth
- of 5 feet; and now, as the 20th century draws to a close,
we are
- challenged by everything from industrial mercury to the
smouldering
- reactors of decommissioned atomic submarines.
-
- The Irish Department of Agriculture will convene an expert
panel on
- April 27-29 to discuss the disposal of tissues from animals
with bovine
- spongiform encephalopathy (BSE). Proper disposal of tissues
from
- infected cattle has implications for both human and animal
safety.
- Safety for human beings is an issue because there is
now unassailable if
- still indirect evidence that BSE causes infections in
man in the form of
- "new variant" Creutzfeld-Jakob disease (nvCJD).1-3
Safety for animals is
- also an issue because BSE-affected cattle could possibly
transmit
- disease to species other than cattle, including sheep,
the species that
- was almost surely the unwitting source of the BSE epidemic.
-
- The first matter to consider is the distribution of infectivity
in the
- bodies of infected animals. The brain (and more generally,
the central
- nervous system) is the primary target in all transmissible
spongiform
- encephalopathies (TSE), and it contains by far the highest
concentration
- of the infectious agent. In naturally occuring disease,
infectivity may
- reach levels of up to about one million lethal doses
per gram of brain
- tissue, whether the disease be kuru, CJD, scrapie, or
BSE. The
- infectious agent in BSE-infected cattle has so far been
found only in
- brain, spinal cord, cervical and thoracic dorsal root
ganglia,
- trigeminal ganglia, distal ileum, and bone marrow.4 However,
the much
- more widespread distribution of low levels of infectivity
in human
- beings with kuru or CJD, and in sheep and goats with
scrapie, suggests
- that caution is advisable in prematurely dismissing as
harmless other
- tissues of BSE-infected cattle.
-
- A second consideration relates to the routes by which
TSE infection can
- occur. Decades of accumulated data, both natural and
experimental, have
- shown clearly that the most efficient method of infection
is by direct
- penetration of the central nervous system; penetration
of peripheral
- sites is less likely to transmit disease. Infection can
also occur by
- the oral route, and the ingestion of as little as 1 g
of BSE brain
- tissue can transmit disease to other cattle.5 Infection
by the
- respiratory route does not occur (an important consideration
with
- respect to incineration), and venereal infection either
does not occur
- or is too rare to be detected.
-
- How can tissue infectivity be destroyed before disposal?
The agents that
- cause TSE have been known almost since their discovery
to have awesome
- resistance to methods that quickly and easily inactivate
most other
- pathogens. Irradiation, chemicals, and heat are the three
commonest
- inactivating techniques. Irradiation has proved entirely
ineffective,
- and only a handful of a long catalogue of chemicals have
produced more
- than modest reduction in infectivity. The most active
of these are
- concentrated solutions of sodium hypochlorite (bleach)
or sodium
- hydroxide (lye). As for heat, even though the agent shares
with most
- other pathogens the feature of being more effectively
damaged by wet
- heat than by dry heat, boiling has little effect, and
steam heat under
- pressure (autoclaving) at temperatures of 121ºC
is not always
- sterilising. To date, the most effective heat kill requires
exposure of
- infectious material to steam heat at 134ºC
for 1 h in a porous-load
- autoclave.6 Exposure to dry heat even at temperatures
of up to 360ºC for
- 1 h may leave a small amount of residual infectivity.7
The standard
- method of incineration, heating to about 1000ºC
for at least several
- seconds, has been assumed to achieve total sterilisation,
but needs
- experimental verification in the light of suggestions
that rendered
- tissue waste might find some useful purpose as a source
of heating fuel.
-
- Thus, TSE agents are very resistant to virtually every
imaginable method
- of inactivation, and those methods found to be most effective
may, in
- one test or another, fail to sterilise. It seems that
even when most
- infectious particles succumb to an inactivating process,
there may
- remain a small subpopulation of particles that exhibit
an extraordinary
- capacity to withstand inactivation, and that, with appropriate
testing,
- will be found to retain the ability to transmit disease.
Also, almost
- all available inactivation data have come from research
studies done
- under carefully controlled laboratory conditions, and
it is always
- difficult to translate these conditions to the world
of commerce. Even
- when the data are applied in the commercial process,
the repetitive
- nature of the process requires vigilance in quality control
and
- inspection to ensure adherence to its regulations.
-
- The final issue that must be addressed is the "lifespan"
of the
- infectious agent after disposal if it has been only incompletely
- inactivated beforehand. Given the extraordinary resistance
of the agent
- to decontamination measures, the epidemiological and
experimental
- evidence indicating that TSE agents may endure in nature
for a long time
- should come as no surprise. The first real clue to this
possibility came
- from the Icelandic observation that healthy sheep contracted
scrapie
- when they grazed on pastures that had lain unused for
3 years after
- having been grazed by scrapie-infected sheep.8
-
- Support for this observation was obtained from an experiment
in which
- scrapie-infected brain material was mixed with soil,
placed in a
- container, and then allowed to "weather" in
a semi-interred state for 3
- years.9 A small amount of residual infectivity was detected
in the
- contaminated soil, and most of the infectivity remained
in the topmost
- layers of soil, where the tissue had originally been
placed--in other
- words, there had been no significant leaching of infectivity
to deeper
- soil layers.
-
- It is therefore plausible for surface or subsurface disposal
of
- TSE-contaminated tissue or carcasses to result in long-lasting
soil
- infectivity. Uncovered landfills are a favourite feeding
site for
- seagulls, which could disperse the infectivity.10 Other
animals might do
- likewise, and if the landfill site were later used for
herbivore
- grazing, or tilled as arable land, the potential for
disease
- transmission might remain. A further question concerns
the risk of
- contamination of the surrounding water table, or even
surface
- waste-water channels, by effluents and discarded solid
waste from
- treatment plants.
-
- A reasonable conclusion from existing data is that there
is a potential
- for human infection to result from environmental contamination
by
- BSE-infected tissue residues. The potential cannot be
quantified because
- of the huge number of uncertainties and assumptions that
attend each
- stage of the disposal process.
-
- On the positive side, spongiform encephalopathy can be
said to be not
- easily transmissible. Although the level of infectivity
to which
- creatures are exposed is not known, it is probably very
low, since sheep
- that die from scrapie, cattle that die from BSE, and
human beings who
- die from nvCJD represent only a small proportion of their
respective
- exposed populations.
-
- Whatever risk exists is therefore extremely small, but
not zero, hence
- all practical steps that might reduce the risk to the
smallest
- acceptable level must be considered. What is practical
and what is
- acceptable are concepts that will be hammered out on
the anvil of
- politics: scientific input, such as it is, already waits
in the forge. A
- fairly obvious recommendation, based on the science,
would be that all
- material that is actually or potentially contaminated
by BSE, whether
- whole carcasses, rendered solids, or waste effluents,
should be exposed
- to lye and thoroughly incinerated under strictly inspected
conditions.
- Another is that the residue is buried in landfills to
a depth that would
- minimise any subsequent animal or human exposure, in
areas that would
- not intersect with any potable water-table source. Certainly,
it has
- been, and will continue to be, necessary in many instances
to accept
- less than the ideal.
-
- Paul Brown
-
- Laboratory of Central Nervous System Studies, National
Institute of
- Neurological Disorders and Stroke, Bethesda, MD 20892,
USA
-
- 1 Will RG, Ironside JW, Zeidler M, et al. A new variant
of
- Creutzfeldt-Jakob disease in the UK. Lancet 1996; 347:
921-25 [PubMed].
-
- 2 Bruce M, Will RG, Ironside JW, et al. Transmissions
to mice indicate
- that 'new variant' CJD is caused by the BSE agent. Nature
1997: 389:
- 498-501.
-
- 3 Collinge J, Sidle KCL, Heads J, Ironside J, Hill AF.
Molecular
- analysis of prion strain variation and the aetiology
of 'new variant'
- CJD. Nature 1996; 383: 685-90 [PubMed].
-
- 4 Wells GAH, Hawkins SAC, Green RB, et al. Preliminary
observations on
- the pathogenesis of experimental bovine spongiform encephalopathy
(BSE):
- an update. Vet Rec 1998; 142: 103-06 [PubMed].
-
- 5 Collee JG, Bradley R. BSE: a decade on--part 2. Lancet
1997; 349:
- 715-21 [PubMed].
-
- 6 Taylor DM. Exposure to, and inactivation of, the unconventional
agents
- that cause transmissible degenerative encephalopathies.
In: Baker HF,
- Ridley RM, eds. Methods in molecular medicine: prion
diseases. Totawa
- NJ: Humana Press, 1996: 105-18.
-
- 7 Brown P, Liberski PP, Wolff A, Gajdusek DC. Resistance
of scrapie
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