Lecture 20 Outline
Biological Warfare (anthrax etc.)
Micrograph of Bacillus anthracis
The face of Biological Warfare
What makes a good biological weapon?
survivability outside of the body, allowing the aggressor to spread store the material, put it in warheads or other dispersal means, and apply the bug in the field
the biological agent must virulent, causing death or severe miasma
the weapon should be quick-acting without a long lag time between dispersal and debilitating illness
the biological agent should be easily dispersed, preferably as a powder, and should also be infectious through person-to-person contact
the agent should be easy to grow in large quantities and not require sophisticated equipment or training
the agent should also be inexpensive to grow in quantity, especially for unfunded terrorists
Generally, the types of agents used as biological weapons cause systemic diseases, hemorrhagic fevers, pneumonias, or involve toxins and biological poisons
Anthrax
Anthrax is caused by Bacillus anthracis, an aerobic gram(+) rod-shaped bacterium
it was first described by Robert Koch (inventor of the agar plate among other things) in 1877
anthrax is usually found in sheep, cattle and goats
the bacteria can make spores that are very resilient in the environment and can persist many decades in soil
grazing animals pick up the bacteria from soil
the bacterium often infects the skin and caused large pustules to form
the cutaneous form of anthrax is very treatable with penicillin although septicemia can ensue in some cases
the pneumonic form of anthrax is 100% fatal unless treated early
it starts with flu symptoms and then suddenly explodes into septicemia, shock and death
unfortunately by the time the obvious symptoms appear it is too late for treatment
Anthrax is the obvious choice for bioterrorists
it can survive many years in soil, can be kept as dried spores easily dispersed
it is very easy to grow the bacterium at low cost with minimal technology
it is a silent killer that can be obtained from infected animals in the field
one gram of anthrax spores is 100 million lethal doses (if evenly dispersed)
it 50 kg of spores were dropped from a plane over a 2 km stretch of sky upwind of a city of 500,000, nearly 1 in 5 is likely to die and many more will be ill
remember that Iraq had tons of this material during the Gulf War
Many suitable bioweapons are intracellular parasites
these microbes are difficult to kill once they are hidden within the patients cells
various typhuses like Rocky Mountain spotted fever can be used
tularemia: survives and grows in phagocytes
brucellosis: undulant fever, grows in macrophages that take it to the lymph nodes
Chlamydia is a common venereal infection
a particular species causes psittacosis (parrot fever) that can be contracted from birds and is quite deadly
Q fever is caused by coxiella and leads to infections and degeneration of the heart
gas gangrene spreads in dead tissue and kills muscle cells
plague is very deadly in its pneumonic form
viral diseases look good on the surface since they can be quite deadly very rapidly
however, often times the virus is not stable outside the body, especially enveloped viruses like HIV
also some viruses can be difficult to grow in the laboratory much less by the ton
smallpox however is easy to grow, very stable, and quite deadly
smallpox stocks still exist and could be used to make weapons
fungi often make spores that are very stable and easily dispersed
histoplasmosis, cryptococcosis, and coccidiomycosis (San Joaquin Valley Fever) are possible candidates
toxins like those from cholera, botulism or shellfish are possible bioweapons
aflatoxin from the fungus Aspergillus is a serious problem for animals and probably humans
this toxin is very easy to grow in large quantity
note however that toxins are not as effective weapons as live microbes
the toxins are essentially just dangerous chemicals
using toxins is more akin to chemical warfare, than biological warfare
the toxin will not reproduce and grow in its host like a microbe would and thus large amounts must be evenly distributed to be effective
How can we protect ourselves?
this is very tough and very expensive
everyone will not wear a gas mask all the time and we can't live in filtered air
we can stockpile antibiotics and vaccines, but this also costs big bucks
detecting bioweapon attacks is crucial it seems
an automated system to alert authorities of the release of an agent could help prevent its spread
ELISA technique
ELISA - enzyme-linked immunosorbent assay
take a plate that has tiny cups cut into it - a 96-well plate
coat the inside of the well with a specific antibody (specific for let's say cholera toxin)
then add the sample to be tested (for cholera toxin)
the antibodies will bind the antigen which they are specific for (the cholera toxin-specific antibodies will bind cholera toxin)
everything that doesn't bind (things that aren't cholera toxin) will be washed away
then a second antibody, specific for the same antigen (cholera toxin) is added
it binds to the antigen making a sandwich having antibody bread and antigen filling
the second antibody has a reporter on it (let's say it is radioactive)
free antibody is washed away and only the antibody-antigen sandwiches remain
by measuring the signal (radioactivity) one can tell how much antigen (cholera toxin) was present in the tested sample
this entire process can be automated
so imagine a system set up in Penn Station New York that samples the air every 30 minutes for anthrax bacilli
