MILITARY MEDICINE, 169, 12:958, 2004
Environmental Mimics of Chemical Warfare Agents
Guarantor: CDR David M. Clabom, MSC USN
Contributor: CDR David M. Clabom, MSC USN
There are several natural and artificial factors that mimic the
effects of chemical warfare agents, thereby causing unwarranted alarm and confusion on the battlefield. Symptoms associated with chemical warfare include paralysis, muscle
tremors, heavy salivation, severe burns, blistering, and corrosive skin injuries among others. Similar symptoms can be
produced from a variety of environmental sources, artificial
and natural. This article reviews several published and unpublished examples of environmental factors that produce syndromes similar to those caused by these agents. Examples of
such mimics include pesticides, blistering exudates from insects and plants, various types of bites, and naturally occurring diseases. The potential for confusion caused by these
factors is discussed and means of discriminating between warfare agents and naturally occurring events are identified. Recommendations for the use of this information and for needed
research are also discussed,
Introduction
n 1997, several U.S. Marines on an exercise in central Arizona
experienced severe blistering symptoms. Several individuals
exhibited very large blisters on their legs, arms, and faces, and
another victim developed a severe case of conjunctMtis in one
eye. Military medical personnel could not identify the source of
the outbreak. However, because the Marines did not appear to
be in distress, most of the victims were returned to duty. Interestingly, the appearance of the blisters reminded the Marines of
images they had seen during training sessions on chemical
warfare. Fearing possible exposure to blistering agents, some
Marines, including at least one company grade officer, were
dissatisfied with their medical treatment and threatened to seek
civilian medical care in the nearest city.
A subsequent investigation by U.S. Navy preventive medicine
personnel identified the probable cause of the blistering disease
as a small rove beetle (family: Staphylinidae) which exudes a
strong blistering agent when disturbed.' These beetles had
probably been flooded out of their normal rodent-burrow habitats by unusually heavy rains and were attracted to the lights of
the Marine encampment. As the beetles brushed against the
humans, the resulting slap stimulated the insects to exude
blistering agent, causing the large blebs and the conjunctivitis
noted in the blistering disease. The outbreak ended a few days
after the last heavy rain. The Marines had in effect suffered a
chemical attack, although the attack was not human in origin,
Although limited in scope, this episode is of interest because
of the response of the Marines to the perceived threat of chemical warfare. It demonstrates the confusion and alarm that ensues when military personnel cannot distinguish between the
symptoms caused by chemical warfare agents and similar
Navy Disease Vector Ecology and Control Center, Naval Air Station, Box 43, Jacksonville, FL 32212-0043.
This manuscript was received for review in August 2003. The revised manuscript
was accepted for publication in January 2004.
Military Medicine, Vol. 169, December 2004
symptoms caused by common environmental factors. These environmental factors are "mimics" of chemical warfare agents.
During the blistering disease incident in Arizona, where there
was no credible threat of a chemical warfare agent, it took
several weeks to find a probable cause. A definite cause was
never identified. The alarm among the Marines was significant,
but in a real wartime scenario, the confusion could be much
worse. One potential way of reducing such confusion would be
the identification of common mimics of chemical warfare agents
before arrival in the area of operations. If such knowledge was
available, medical personnel would be better able to discrimihate between indigenous maladies and the emergencies caused
by intentional use of warfare agents. As the Arizona incident
demonstrates nonmedical personnel can also benefit from this
knowledge.
On the other hand, such information might delay proper
treatment for chemical agent victims. Indeed, the speed with
which medical personnel obtain proper diagnosis and the rapidity with which they apply proper therapeutic measures can
greatly influence mortality rates after a chemical attack. Conversely, false alarms can also degrade a unit's war-fighting capabilities. The defensive measures used by the U.S. military on
the chemical battlefield are effective, but they are also very risky
and are likely to impair performance and decision making. For
example, Headly noted that antidotal atropine increases skin
and rectal temperature and compromises thermoregulation, especially in soldiers wearing protective clothing or working in hot
environments.
Unnecessary alerts might also result in the wasteful employment of limited protective gear, requiring rapid replenishment to
deployed units. This situation would be particularly important
in a war zone where supply lines can be extended and unreliable.
Weiner stated that to implement a successful chemical/biological defense response, the following three questions must be
answered" (1) How do we know the outbreak of a disease or
malady is a chemical/biological attack and not a natural epidemic? (2) What agents are being used by hostile forces? (3)
What countermeasures are available?
The first question proposed by Weiner emphasizes the importance of knowing the epidemiology and geographic distribution of chemical agent mimics. This article is intended as a
nontechnical introduction to possible chemical warfare mimics,
natural and man-made. It is by no means comprehensive, but
may serve as a general guide in predeployment planning.
Artificial Mimics of Chemical Warfare Agents
Many of the insecticides used in agriculture, public health,
and home pest control are organophosphates, a class of chemicals that includes the nerve agents VX, tabun, and sarin. The
signs and symptoms of severe intoxication with these pesticides
are very similar, although not identical, to those caused by the
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Environmental Mimics of Chemical Warfare Agents
warfare agents. The primary difference between commercial
pesticides and these chemical agents is their levels of toxicity.
For instance, sarin is approximately 1,000 times more toxic
than parathion, one of the most toxic agricultural chemicals.
Even so, a severe exposure to high levels of the more toxic
agricultural or public health insecticides would be difficult to
distinguish from a chemical attack. Exposures to agricultural
pesticides could occur simply by traversing a recently treated
field. Chemical agent detection systems might indicate chemical
warfare agent exposure in such an environment, further complicating the situation. Other potential exposures could occur
through ingestion of local insecticide-contaminated food or water. The author once inspected the warehouse of a charitable
organization that was inadvertently providing seed corn as part
of a food program. The seed corn had obviously been treated
with a pesticide to prevent insect and fungal infestations during
germination. Ingestion could have caused severe insecticide intoxication. A victim of such a severe exposure may not have time
to report the initial effects before losing consciousness and, in
fact, may not even know of his/her exposure. The similarity in
symptoms, combined with uncertainty of how a victim was exposed, would make pesticide poisoning very difficult to distinguish from the intentional use of a chemical agent in an operational environment lacking equipment for definitive chemical
analysis,
Many organophosphate insecticides such as parathion, malathion, and chlopyrifos are used in agriculture worldwide. AIthough significant legal restrictions have been placed on the use
of these chemicals in the United States, American laws are not
applicable in other countries, therefore pesticides may be in use
elsewhere long after they have been removed from American
markets.
Many of the newer pyrethroid insecticides are replacing the
older acetylcholinesterase inhibitors that include organophosphates and the carbamates. Intoxication with pyrethroids, although perhaps less likely, can cause some of the same symptomatology, causing false alarms. Other pest control products,
such as N,N-diethyl metatoluamide repellent may provide falsepositive results when applied to chemical agent detector paper
used by U.S. military personnel (D.M. Claborn, unpublished
observation).
Because of the potential for false alarms caused by agricultural compounds, predeployment intelligence estimates should
include pesticide use in the area of interest. Specific information
should include which pesticides are used, which crops are
treated, what time of year to expect treatments, and how pesticides are applied. Personnel should be aware of signs that a field
has been treated recently (e.g., numerous dead rodents or birds,
a wet deposition when surrounding fields are dry, and even
warning placards placed at the borders of fields). This knowledge could be useful in preventing false alarms and avoiding
hazardous environments,
Natural Mimics of Chemical Nerve Agents
Some animal envenomations cause symptoms similar to
those caused by nerve agents. The bite of an elapid, a snake in
the same family as the cobras and kraits, can result in heavy
salivation, paralysis, muscle tremors, and death. If the victim is
unable to communicate, his condition could be attributed to a
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chemical agent. This scenario is unlikely, but it demonstrates
the potential for confusion caused by animal envenomations. A
more likely scenario is provided by sea snakes (family Hydrophiidae}. Their venoms contain potent neurotoxins that cause paralysis, respiratory failure, and even death. Death occurs when
the venom binds to acetylcholine receptors at the neuromuscular junction. Although this is a different toxic mechanism from
that of warfare agents that inhibit acetylcholinesterase, similar
symptoms are elicited. Complicating matters even further is the
fact that the victim may not realize that he/she has been bitten;
he/she may not feel the snake attack and the fang punctures
may be invisible to the naked eye.
Another well-documented chemical mimic is that of tick paralysis, a condition in which the anesthetic injected by a feeding
tick causes progressive numbness and paralysis. If unrecognized, this condition can be rapidly fatal but it is easily cured by
removal of the tick. It is characterized by ascending symmetric,
flaccid paralysis. Tick paralysis can be confused with GuillainBarr syndrome, botulism, and myasthenia gravis; therefore,
these conditions could also be considered chemical and biological mimics by association.
Fortunately, these events would likely occur individually,
whereas nerve agents used in warfare or terrorism would probably affect several people and would be accompanied by other
observable environmental effects such as bird deaths and fish
die-offs. Nevertheless, any person showing signs of nerve disorders, especially on a sparsely populated battlefield, would always be cause for concern.
Mimics of Vesicants
Numerous environmental factors can produce dermatological
symptoms similar to those caused by vesicating warfare agents
like mustard and Lewisite. In the outbreak of blistering disease
in Arizona, diagnostic considerations included contact dermatitis, thermal or chemical bums, impetigo, herpes simplex/zos-
ter, porphyria, pemphigus, dermatitis herpetiformis, and dermatological manifestation of coccidiomycosis. This range of
possibilities includes everything from physical causes (thermal
bums) to communicable disease (coccidiomycosis). Chronic
skin conditions must also be considered. Blistering could be
something as common as poison ivy or sunburn, both of which
could affect several people at once. (Interestingly, a recent event
of "chemical warfare" using poison ivy was reported from Haiti,
when a group of government supporters attacked a group of
protesters with poison-ivy spiked water). Other conditions
such as impetigo or pemphigus, however, would probably be
limited in occurrence and would require extensive medical expertise to diagnose.
Several insects and other arthropods are known to cause
blisters as discussed earlier. Rove beetle dermatitis has been
documented in Tanzania, Australia, Okinawa, a Vietnam, 14
Egypt, a Uganda, Kenya, 7 and Peru. In at least one instance,
an entire village was evacuated in response to these beetles,
indicating that symptoms can occur in several persons at once,
as would be expected with chemical warfare. Another beetle, the
meloid known as the blister beetle, can also cause impressive
blistering, although victims usually remember handling the insect before the onset of the blisters. This is not true of rove
beetles.
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Skin irritants have also been documented with millipedes and
caterpillars. The urticaria caused by caterpillars would probably
not be confused with that caused by a blister agent like muso
tard, but it could be confused with the symptoms of phosgene
oxime, another type of chemical agent. Phosgene oxime is a
urticant or nettle agent that causes a corrosive type of skin
injury. It is not a true vesicant because it does not cause
blisters, but it affects the skin, eyes, respiratory system, and
gastrointestinal tract. Dermal symptoms include an erythematous ring within 30 s of exposure. An eschar forms in the affected area within week and the skin sloughs off after approximately 3 weeks. Similar symptoms that can be confused with
this urticaria can be caused by urticating spines on certain
caterpillars. Large-scale urticaria can be induced when caterpillar spines of large populations become airborne and spread
over a large area. In one of the largest examples of caterpillarinduced urticaria, 600 of 6,000 soldiers were affected. l, The
urticarial conditions caused by caterpillars would not be as
severe as the symptoms caused by phosgene oxime, but dermatological conditions in multiple victims would certainly cause
some concern in a potential chemical warfare environment,
The presence of chemical mimics can obviously cause unwarranted alarm and degrade the war-fighting capacity of a unit.
Deployments in environments with a risk of chemical agent
exposure are associated with intense fear of chemical warfare.
Psychologically, the impact of perceived or actual chemical attacks results in casualties from acute stress disorder, grief,
anger, scapegoating, and somatization disorders. During the
Gulf War, some military personnel exhibited panic, hyperventilation, and an inability to don respirators even when chemical
alarms were sounding. Obviously, the threat of exposure to
chemical agents, whether real or perceived, has a lasting and
adverse impact on human health,
For these reasons, a complete analysis of potential mimics
should be part of any predeployment intelligence effort for areas
of imminent or existing conflict. Especially important is a thorough knowledge of pesticide use, including type, formulation,
crop usage, and targets of the most toxic chemicals. This information could be used by unit commanders not only to help
identify false alarms, but also to avoid exposures that might
predispose individuals to serious intoxication in the event of a
subsequent chemical warfare event. Other information that
would be useful would be the types of allergenic plants, "blistering" or urticating insects, and naturally occurring disease
that might cause concern. Great care would be needed in using
this information. A delay in diagnosis could be fatal to victims of
a chemical attack and any suspect case would need to be treated
appropriately. However, proper assessment of mimics could prevent dangerous misdiagnoses and improper treatment. Perhaps
as importantly, it could prevent the unnecessary use of limited
chemical protective postures in environments where this would
be detrimental to unit effectiveness and individual health. In
addition, a postdeployment assessment of mimics could allay
fears of exposure to warfare agents.
A similar situation exists with the biological agents that also
have numerous mimics. Natural occurrences of diseases such
as anthrax and plague may be confused with intentional outbreaks caused by weaponized strains of the same agents. Also,
diseases that are similar in presentation such as monkey pox
Military Medicine, Vol. 169, December 2004
Environmental Mimics of Chemical Warfare Agents
and smallpox may be confused. This article is not intended to
address biological agents that are thoroughly reviewed
elsewhere. 4-6
Currently, acquisition of information on chemical warfare
mimics is not standardized or codified. However, the Navy Disease Vector Ecology and Control Centers in Jacksonville, Florida, and Bangor, Washington, are working jointly to acquire
certain parts of this information as part of other programs. The
mission of these centers includes acquiring information on the
risk ofvector-borne disease throughout the world. An important
part of this information is the types of agricultural pesticides
used in areas of strategic interest. Because many disease vectors develop resistance to insecticides through incidental and
long-term exposure to agricultural insecticides, information on
the local use of insecticides suggests the resistance status of
local vectors. This information, in turn, drives decision making
on what vector control measures are appropriate for troops
deploying to a given area. Although the initial purpose for gathering this information is independent of chemical warfare miraics, it can be used to identify false alarm risks by identifying
potential chemical mimics and geographical areas where such
mimics are common. Some of the other mimics are identified as
medical risks in the country-specific literature disseminated by
the Armed Forces Pest Management Board, the Armed Forces
Medical Information Center, and the Defense Pest Management
Information Analysis Center.
This type of information is most useful when it is available to
the troops at risk for exposure to chemical warfare agents and
mimics of chemical agents. Specifically, this and other preventive medicine information can aid the line officer and others
responsible for troops in the field. Differential diagnosis of potential chemical agent symptoms and the mimics that may
cause confusion should be presented at any advanced course on
chemical warfare agents, whether for medical or nonmedical
audiences. Proper identification of environmental mimics can
prevent unnecessary alarm and injuries, and reduce waste of
expensive chemical protective gear. However, this information
must always be accompanied by a strong emphasis on proper
treatment and first-aid for any suspected victim.
Acknowledgments
thank CDR Kenneth Stein, MSC USNR, CDR Harvey Adkinson, MSC
USN, Dr. Andrew Beck, and CDR Joseph Conlon, MSC USN (Ret.), for
their efforts in reviewing this article and contributing ideas.
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