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[no subject]
Hope this helps. Any of you who read this far can give yourself a pat on the=
=20
back.
Charles.
"You can regale your companion if you wish with the story of the time you=20
killed the Mexican with a short arm chin jab followed by a hand-edge chop to=
=20
the Adam's apple, but this might distress her. Better stick to saying=20
modestly at the right moment, 'I only know five ways of killing a man with a=
=20
single blow."
"You can regale your companion if you wish with the story of the time you=20
killed the Mexican with a short arm chin jab followed by a hand-edge chop to=
=20
the Adam's apple, but this might distress her. Better stick to saying=20
modestly at the right moment, 'I only know five ways of killing a man with a=
=20
single blow."
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<HTML><FONT FACE=3Darial,helvetica><FONT SIZE=3D2>There seems to be some co=
nfusion about anthrax so I thought this might help:
<BR>
<BR><I>B. anthracis</I>, the causative agent of anthrax, is a Gram positive,=
aerobic or facultatively anaerobic, endospore=E2=80=93forming, rod=E2=80=
=93shaped bacterium approximately 4 =C2=B5m by 1 =C2=B5m, although under the=
microscope, it frequently appears in chains of cells. In the presence=
of oxygen, and towards the end of the exponential phase of growth, one elli=
psoidal spore is formed in each cell; this does not swell the sporangium and=
is generally situated centrally, sometimes sub=E2=80=93terminally.Under ana=
erobic conditions and in the presence of bicarbonate (HCO3), the vegetative=20=
cell secretes a polypeptide (poly=E2=80=93( =E2=80=93 D=E2=80=93glutamic aci=
d) capsule. The capsule is formed <I>in vivo</I> and is one of the two virul=
ence factors of <I>B. anthracis</I>. It is also a primary diagnostic aid.
<BR>
<BR>When conditions are not conducive to growth and multiplication of the ba=
cilli, they tend to form spores. Sporulation requires the presence of free o=
xygen; within the anaerobic environment of the infected host the organism is=
in the vegetative form. Although the vegetative forms of <I>B. anthracis</I=
> grow and multiply readily on or in normal laboratory nutrient agars or bro=
ths, the evidence is that they are more "fragile" than the vegetative forms=20=
of other <I>Bacillus</I> species, dying more spontaneously in simple environ=
ments such as water or milk, and more dependent on sporulation for species s=
urvival.=20
<BR>
<BR>The spore forms are markedly resistant to biological extremes of heat, c=
old, pH, desiccation, chemicals (and thus to disinfection), irradiation and=20=
other such adverse conditions. Therefore, the spore forms are the predominan=
t phase in the environment and it is very largely through the uptake of spor=
es that anthrax is contracted. Within the infected host the spores germinate=
to produce the vegetative forms which multiply, eventually killing the host=
. A proportion of the bacilli released by the dying or dead animal into the=20=
environment (usually soil under the carcass) sporulate, ready to be taken up=
by another animal.</FONT><FONT COLOR=3D"#000000" SIZE=3D3 FAMILY=3D"SANSSE=
RIF" FACE=3D"Arial" LANG=3D"0"></FONT><FONT COLOR=3D"#000000" SIZE=3D2 FAMI=
LY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0">
<BR>
<BR>Human beings appear to be fairly resistant to anthrax infection. For exa=
mple, in 4 mills in the USA, in which unvaccinated workforces, varying in si=
ze from 148 to 655, were "chronically exposed to anthrax", annual case rates=
were only 0.6 to 1.4%. In one mill, workers were found to be inhaling 600 t=
o 1300 anthrax spores over an 8=E2=80=93hour shift without ill effect and in=
two goat=E2=80=93hair mills, <I>B. anthracis</I> was recovered from the nos=
e and pharynx of 14 of 101 healthy persons. Despite extensive exposure to an=
thrax, cases among workers in wildlife reserves are exceedingly rare.
<BR>
<BR>Unfortunately no one knows the exact amount of anthrax needed to infect=20=
a human but the recorded inhalation LD50s in non=E2=80=93human primates rang=
e from 2500 to=20
<BR>760 000 spores . The US Department of Defence bases its strategies on an=
estimate that the LD50 for humans is 8000 to 10 000 spores. However the onl=
y hard data on inhalation infectious doses in humans come from the studies i=
n goat hair processing mills (see above). In any event, substantial exposure=
is evidently necessary before the risk of inhalation anthrax becomes signif=
icant. In a recent study the highest levels found in air sampled 3 to 9 m do=
wnwind from disturbed dry, dusty anthrax carcass sites in Namibia were 20 to=
40 colony=E2=80=93forming units of spores per cubic metre. This corresponds=
to the conservative estimate that it would require about 2.5 minutes for an=
average human undergoing moderate activity to inhale 1 spore. It is, furthe=
rmore, well established that, at sizes above 5 =C2=B5m, particles face incre=
asing difficulty in reaching the alveoli of the lungs. The likelihood of inh=
aled spores penetrating far enough to induce inhalation anthrax therefore de=
pends greatly on the size of the particles to which they are attached.</FONT=
><FONT COLOR=3D"#000000" SIZE=3D3 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=
=3D"0">
<BR>
<BR></FONT><FONT COLOR=3D"#000000" SIZE=3D2 FAMILY=3D"SANSSERIF" FACE=3D"Ar=
ial" LANG=3D"0">There is, in fact, no conflict between the statements that h=
umans are fairly resistant to fatal anthrax infection and the possible aggre=
ssive use of anthrax spores. The "worst case" natural contamination in the e=
nvironment is found at the carcass sites of animals that have died of anthra=
x. In the Namibian study of 106 such sites, the highest contamination level=20=
found was just over 1 million anthrax spores per gram of soil, but 79% had l=
ess than 1000 per gram and 25% less than 10 per gram. Levels in other types=20=
of inadvertently contaminated environments (soils at tannery sites, horsehai=
r plaster, etc.) rarely exceed a few units or tens of spores per gram. Natur=
al environmental exposure to infectious doses in the normal course of human=20=
life and endeavour is, therefore, a fairly unlikely event.=20
<BR>
<BR>Aggressive scenarios, in contrast, envisage exposures to overwhelmingly=20=
massive doses (many millions of spores) which can only be created artificial=
ly. The Figure of 100 kg of dried anthrax spores, given in one article on th=
e subject as technically feasible for aggressive delivery, represents dose l=
evels in the order of 10^13 human LD50s. It must be supposed that this could=
cause substantial devastation to human and animal communities within select=
ively targeted areas.
<BR>
<BR>From a scenario point of view this means that any terrorist wanting to u=
se anthrax as a weapon is going to have to find some way of distributing lar=
ge amounts of it over a large enough area to cause major inconvenience witho=
ut alerting the white-hats to what they're up to. Aum Shinrikyo actually tes=
ted an anthrax release system on the roof of their headquarters but apparent=
ly abandoned it in favour of nerve gas.
<BR>
<BR>Hope this helps. Any of you who read this far can give yourself a pat on=
the back.
<BR>
<BR>Charles.
<BR>
<BR>"You can regale your companion if you wish with the story of the time yo=
u killed the Mexican with a short arm chin jab followed by a hand-edge chop=20=
to the Adam's apple, but this might distress her. Better stick to saying mod=
estly at the right moment, 'I only know five ways of killing a man with a si=
ngle blow."
<BR>
<BR>
<BR>"You can regale your companion if you wish with the story of the time yo=
u killed the Mexican with a short arm chin jab followed by a hand-edge chop=20=
to the Adam's apple, but this might distress her. Better stick to saying mod=
estly at the right moment, 'I only know five ways of killing a man with a si=
ngle blow."
<BR>
<BR>
<BR>
<BR>
<BR>
<BR></FONT></HTML>
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