(anthrax) has a unique place in medical history. The name Bacillus
anthracis derives from the Greek word for coal, anthrakis,
since the disease manifests itself as black, coal-like lesions on
human skin. It was the first bacterium discovered by Robert Koch
in 1877 exhibited then for the first time to cause infectious disease.
This led to the production of the first vaccine by Louis Pasteur
in 1881, when he employed attenuated live B. anthracis
to protect sheep against anthrax. Species of the genus Bacillus
are gram-positive, and form endospores that are strictly or facultatively
aerobic. Most of the nearly one hundred Bacillus species
are ubiquitous mostly in soil but also in water, and they are mostly
encountered in medical bacteriology as airborne germs; Bacillus
anthracis, the cause of the disease anthrax is an exception
to the general manifestation of the Bacillus genus due
to its increased risk. Anthrax has increasingly been used as a terrorist
tool since the September 11th terrorist crimes in the US. Hence, early detection and deterrence of biological
agents such as anthrax, as well as its containment and control,
decontamination, and medical treatment for those infected is of
extreme priority. In environmental forensics while employing the
techniques of DNA finger printing (Mitochondrion and Plasmid) and
other key bio-molecular marker strategies, law enforcement should
also be in a position to trace back to the source of such agents
for criminal prosecution purposes. NSF has now earmarked grants
to a private research firm to decipher the genetic DNA map of Bacillus
anthracis to be able to trace out whether various specimen
found in different locations are of the same origin. A comprehensive
search of MEDLINE databases from January 1966 to September 2001
using the Medical Subject Headings anthrax, Bacillus anthracis,
biological weapon, biological terrorism, biological warfare,
and biowarfare led to the conclusion that there is an immense
increasing interest on the part of medical, clinical, scientific,
public health management and law enforcement communities on the
these topics, particularly within the past decade.·
For instance, a working group comprised of representatives from
major academic medical centers and research, government, military,
public health, and emergency management institutions and agencies,
who met to develop consensus-based recommendations for measures
to be taken by medical and public health professionals following
the use of anthrax as a biological weapon against a civilian population,
exemplifies such emergent efforts (Journal of American Medical Association,
1991; 281:135-1745). Specifically, consensus recommendations
were made regarding the diagnosis of anthrax, indications and justifications
for vaccination, therapy for those exposed, post-exposure prophylaxis,
decontamination of the environment, and additional research and
development needs. Of the numerous biological agents that may be
used as weapons especially against civilians, the Working Group
on Civilian Biodefense has identified a limited number of organisms
that could cause disease and deaths in sufficient numbers to cripple
a city or region. Not surprisingly, anthrax was designated as one
of these most serious diseases. High hopes were at one juncture
vested in the Biological Weapons and Toxins Convention, which prohibited
offensive biological weapons research or production and was signed
by most countries. However, Iraq
and the former Soviet Union (currently Russia),
both signatories of the convention, have subsequently acknowledged
having offensive biowarfare programs; a number of other countries
besides the U.S. are also believed to
have such programs or certain stockpiles of these agents, as may
have some autonomous terrorist groups. The possibility of a terrorist
attack using bioweapons would be especially difficult to predict,
detect, or prevent; thus, it is among the most feared terrorist
scenarios, since the technology of production of
such biological agents is textbook based in most cases.
For centuries, anthrax has caused disease in animals and, uncommonly,
serious illness in human throughout the world. In
fact, the use of biological agents in clandestine warfare is deemed
to date back to a few millennia. Dropping covertly dead animals
in adversaries’ water supply such as in wells and “qanat” (underground
aquifers) has been practiced as far back as there is any historical
accounts of human clashes. In antiquity, it was believed that the
dead corpse’s soul would “hunt” the water, thereby making it lethally
poisonous. In retrospect, however, it actually turned out the corpse
was the hospitable source of nutrients where the proliferation of
deadly microorganisms like B. anthracis (anthrax), Colostridium
botulinum (botulism), Yersinia pestis (plague), and
viral smallpox, cholera (Vibrio cholerae), typhoid fever (Salmonella
typhi) and dysentery were the actual culprits behind the endemic
epidemics that at times annihilated an entire city in a short time.
Research on anthrax as a biological weapon began more than 80 years
ago. Today, at least 17 nations are believed to
have offensive biological weapons programs; it is
uncertain how many other countries or clandestine terrorist groups
are actively engaged in the field. Iraq
has acknowledged producing and weaponizing anthrax.
This is not surprising as Iraq
not only used chemical lethal agents against Iranian civilians,
but also against its own Kurdish minority in the north in the late
80’s. There is henceforth, sufficient evidence to conclude that
certain autonomous terrorist groups are actively working on the
acquisition, production and illegal application of biological and
chemical agents worldwide.
Naturally occurring Anthrax is generally an enzootic disease of
worldwide occurrence. An enzootic disease is endemic to a population
of animals, i.e., its occurrence changes little over time. Anthrax
in contrast, as an epizootic disease attacks large number of animal
species, similar to a human epidemic. Domestic hoofed herbivores
such as sheep, goat, cattle, camels, horses, lamas, and antelopes
are the usual victim of anthrax. For instance, during 1945 alone,
one million sheep died of anthrax infection in Southwest
Iran alone, with a simultaneous widespread cutaneous human anthrax.
Domestic animal vaccination since then has dramatically reduced
the animal mortality rate. It could, however, be transmitted to
human via contact with such infected animals. Human contact with
anthrax leads to the sub-cutaneous inoculation of spores through
incidental skin abrasions. The inhalation of spore-laden dust in
the range of 1-10 μm in particular, will lead to the less frequent,
nonetheless, more dangerous pulmonary infection; in occupational
hazard, this latter cases is also referred to as “wool-sorter’s
disease. B. anthracis spores may remain viable for years, and similar
to Clostridium botulinum (responsible for foodborne botulism) are
highly resistant to physical and, or chemical disinfecting agents.
In the U.S.
a widespread veterinary vaccine has minimized the sources of the
disease. Contaminated imported agricultural goods on occasion, has
resulted in the quarantine of goods from endemic areas.
B. anthracis is comprised of a capsule made up of polymers of D-glutamic
acid, which is not immugenic in itself. This envelope is antiphagocytic,
albeit crucial for full virulence. The bacterium also excretes two
plasmid-coded exotoxin eliciting protective antibodies: edema
factor, which is a calmodulin-dependent adenylate cyclase that
causes the elevation of intercellular cAMP, responsible for the
severe dark edema as observed in B. anthracis infections; and, lethal
toxin which is auxiliary to additional adverse effects.
anthrax: Approximately 90 percent of human cases of anthrax
are of cutaneous category. For instance, between 1944 and 1994,
224 cases of cutaneous anthrax were reported in the US;
the number was substantially higher in other less developed regions
of the world. Upon skin contact with the organism or its spores
that germinate, an itchy papule that resembles an insect bite is
induced within 1-2 days, It rapidly leads to a painless ulcer 1-3
cm in diameter, black severely swollen “malignant pustule” with
a characteristic necrotic (dying) area in the center which eventually
crusts over. The organism may invade the general circulation via
regional lymph nodes. Even though some cutaneous based anthrax cases
remain localized and ultimately heal spontaneously, the overall
mortality rate in untreated cutaneous anthrax is about twenty percent.
Deaths are rare with appropriate local and oral antimicrobial therapy,
anthrax: There were 18 reported cases of inhalational anthrax
cases in the United
States between 1900 to 1978, mostly from special
risk groups, i.e., those who directly worked with domestic animals
and products like wool; it is noteworthy to cite two of the 18 infected
were laboratory workers. The initial symptoms may resemble a common
cold or flu-type symptoms. These symptoms can worsen resulting in
serious breathing and convulsion problems, while causing detrimental
breathing in some cases when untreated in time. After typically
several days, but in rare circumstances after prolonged delays of
up to 60 days, the disease fully manifests itself. Also referred
to as “woolsorter’s disease” in the past, pulmonary anthrax is caused
by inhalation of spores in the dimension range 1-10 μm. There
are industrial micro-encapsulation technologies that would lend
itself to the stabilized production of spores in such detrimental
dimension range. The naturally occurring spore colonies are generally
much larger than the above range. When developed as a biological
weapon, the organism is encapsulated in envelopes that are sufficiently
small to increase their penetrating effectiveness via the nasal
canal and the pulmonary system. Pulmonary anthrax is characterized
by progressive hemorrhagic lymphadenitis, i.e., inflammation of
the lymph nodes. The mortality rate, if left untreated, approaches
one hundred percent. Based on primate data, it has been estimated
that the LD 50 (lethal dose sufficient to kill 50% of persons exposed
to it) for human is 2500 to 55,000 inhaled anthrax spores.
anthrax: Although very rare, this form of anthrax manifests
itself by the ingestion of spores through eating inadequately cooked
meat or unsanitized fruits and vegetables. The gastrointestinal
disease form of anthrax is characterized by an acute inflammation
of the intestinal tract. Initial signs of nausea, loss of appetite,
vomiting, and fever are followed by abdominal pain, vomiting of
blood, and severe diarrhea. Intestinal anthrax results in death
in 25% to 60% of cases when untreated in time. Gastrointestinal
anthrax is more frequent in animals, however.
B. anthracis is readily recovered from clinical specimens.
It is, however, often present in massive numbers in the form of
colonies. This organism appears under the microscope as blunt-ended
bacilli, occurring singly, in pairs, or more often as long chains.
They do not sporulate in clinical samples, but do so on culture
medium. The spores are oval and centrally located. On blood agar,
these colonies are large, grayish, non-hemolytic with irregular
boundaries. Gram-positive stain of culture smear showing non-staining
spores. Contrary to many other Bacilli, B. anthracis is non-motile,
and encapsulated in vivo. A direct immunofluorescence assay aids
in the identification of the organism. Extreme caution should be
taken to prevent transmission via aerosols when handling this organism
in the laboratory.
Treatment and prevention:
The symptoms of disease vary depending on the mode of contraction,
but symptoms usually occur within 7 days. Direct person-to-person
spread of anthrax is extremely unlikely to lead to a contagious
manifestation of the disease. Communicability is not, therefore,
a concern in managing or visiting with patients with inhalational
anthrax. The only way to acquire infection of the disease anthrax
is to be directly exposed to large numbers of spores of the microbe.
Naturally occurring B. anthracis is sensitive to antibiotics: ciprofloxacin,
penicillin, and doxycycline. Careful investigation must be followed
to assess the possible resistivity of a specific organism that may
have been mass-produced through genetic engineering, adaptation
and, or other biotechnology techniques for the mere terrorist applications.
A cell-free vaccine is available for those in high- risk occupations.
Because anthrax is considered to be a potential agent for use in
biological warfare, the Department of Defense (DoD) has had mandatory
vaccination of all active duty military personnel who might be involved
in conflict since the 1991 Desert Storm and Desert Shield Operations
in Persian Gulf against Iraq. The vaccine is reported
to be 93% effective in protecting against anthrax. The anthrax vaccine
is manufactured and distributed by BioPort, Corporation, Lansing, Michigan. The vaccine
is a cell-free non-infectious sterile ultra-filtrate (less than
0.05 μm at minimum) form of the culture of an attenuated strain
of Bacillus anthracis that contains no dead or alive bacteria.
The final product contains no more than 2.4 mg of aluminum hydroxide
as adjuvant base, a substance that when injected with an antigen,
serve to enhance the immunogenicity of that antigen. Anthrax vaccines
intended for animals should not be used in humans. Pregnant women
should be vaccinated only if absolutely necessary. The immunization
consists of three subcutaneous injections given 2 weeks apart followed
by three additional subcutaneous injections given at 6, 12, and
18 months. Annual booster injections of the vaccine are recommended
thereafter. Mild local reactions occur in
30% of recipients and consist of slight tenderness and redness at
the injection site. Severe local reactions are infrequent and consist
of extensive swelling of the forearm in addition to the local reaction.
Systemic reactions occur in fewer than 0.2% of recipients.
Epitomizing, however, it is the ultimate better understanding of
the exact macro-molecular toxins interactions in the cell and as
released by the B. anthracis that would truly relieve us of the
dangers associated with anthrax. Upon diagnosis of the infection
stage, large amount of toxins presumably comprised of three proteins,
has already been released independently into the blood stream to
be reunited in cells. Antimicrobial drugs are not any longer effective
against the control of these already circulating toxins in the body
at such juncture. This endeavor falls in the realms of the emerging
field of proteomics, an area where recent findings could help design
drugs to neutralize in vivo presence of anthrax toxins. Looking
back at the twentieth century, one might summarize the three scientific
breakthroughs: atom, computer and gene, the latter of which has
now mapped out the up to one hundred thousands human genes, which
in turn is comprised of up to one billion nitrogenous pairs on the
forty six chromosomes. A harmonic integration of these three breakthroughs
will be the main theme of the current century, in which proteomics,
the science of identification and quantitation, structural elucidation,
mechanistic functions, etc. of up to a billion proteins is on the
scientific community agenda. The two research groups at Harvard Medical School
and University of Wisconsin (R. J. Collier &
A.T. Young, Nature, November 8, 2001, 415: 15-26) have
striven to tackle that goal for anthrax. They just reported the
first anthrax protein called protective antigen, binds to a cell
receptor and facilitates the entry into the cell of the other two
proteins, which in turn while serving concurrently as hydrolytic
enzymes impair the body’s defense mechanism. One hypothesis postulates
finding a novel method of eliminating the reunion of these two enzymes
as a means of disease prevention and control. Notwithstanding, the
structural elucidation and molecular based mechanism of action of
such protein toxins are the pre-requisites toward the ultimate eradication
of not only anthrax but also of other similar biological borne diseases.
Such exciting multi-disciplinary approach, should ultimately pave
the way toward deciphering the actual effect at the molecular level.
Another possibility might be to carry out molecular modeling of
these enzymes after their structures are fully elucidated and based
on x-ray diffractions among other spectroscopic techniques. Then,
utilizing combinatorial chemistry one should then be able to model
a suitable competitive inhibitor that binds to the enzyme, thereby
incapacitating it swiftly. Alternatively, if one could pinpoint
the exact intracellular receptor to which the enzyme binds, one
should then strive to block that receptor site with benign antagonists.
For now, it is important to note that because of the resistance
of endospores to chemical disinfectants, autoclaving is the most
reliable means of decontamination. Gamma irradiation of suspicious
objects coupled with strong magnetic fields is finding increasing
merit, nevertheless, despite its extreme cost and retrofitting schemes.
Upon sufficiently suspecting the presence of a contaminated object,
the ventilation system must immediately be turned off, the section
closed off, and the area evacuated. Law enforcement authorities
must be contacted at once. A list of those individuals who were
in the immediate contaminated area should be reported to the authorities
for their immediate medical evaluation, monitoring and possible
treatment. Federal and State Departments of Health and Human Services
and Center for Disease Control among other agencies maintain excellent
sources of information accessible via Internet and phone systems.
Finally, other biological agents such as smallpox are far more dangerous
than anthrax due to their immediate epidemic characteristics. An
integrated vaccination program, possibly in coordination our allies
for a common stockpile is, therefore, warranted.
Literature Cited and Further Suggested in-depth Readings:
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Journal of American Medical Association,1991; 281:135-1745.
Williams, A. Strohl, D., Harciet, Rosse, F., Lippincotes Illustrated
Reviews: Micorbiology, 2001.
Carter A, Deutsch J, Zelicow P., Catastrophic terrorism. Foreign
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and Practices of Infectious Disease.New York,
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Zilinskas RA. Iraq's biological weapons: the past as future?
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DC: US Dept of Health and Human Services; 1995.
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Anthrax Vaccine Immunization Program in the U.S. Army Surgeon General's
Office can be reached at 1-877-GETVACC (1-877-438-8222). http://www.anthrax.osd.mil
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A modified derivation of the ancient
Greek word Anthrakis meaning coal attributed to its
black color, was later used according to IUPAC Nomenclature to denote
a class of poly-aromatic hydrocarbons referred to as Anthracenes,
and as derived form coal, tar and heavy fossil based products.