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606 S P E C I A LT Y P R A C T I C E I N C R I T I C A L C A R E

Chemical Agents ENVENOMATION
Chemical agents are super-toxic chemicals used to poison Venomous animals can be land-based or marine-based,
mass victims. The chemicals are similar to hazardous and their distribution ranges from broad to very specific
industrial chemicals, but hundreds of times more toxic. locations. Exposure of humans to venom produces a large
For example, while the Sarin attack on the Tokyo subway and varied range of symptomatology, which often results
in 1995 killed 12 people, there were also 1039 injuries, in an emergency presentation. It is therefore important
and at least 4000 people with psychogenic symptoms. 147 for critical care nurses to be familiar with the types of
Sarin is approximately 60 times more toxic than methyl- potentially venomous animals inhabiting the catchment
isocyanate. To demonstrate this perspective: a leak of area of their health setting. Be familiar with the presenta-
methylisocyanate from a factory in Bhopal, India in 1984 tion and management of specific envenomations, includ-
caused 200,000 people to be affected, 10,000 severely ing antivenom availability. Contact the local poison
affected and 3300 deaths. Relatively small quantities of a information centre for advice from expert toxicologists
military grade chemical agent could therefore have the (see Online resources). Common envenomations across
same capability to produce large numbers of casualties Australia and New Zealand are described below.
(symptomatic and psychological). 147,148
Redback/Katipo Spider Bite
Biological Agents Description and incidence

Biological agents are living organisms or toxins with the
capacity to cause disease in people, animals or crops. The redback spider (Latrodectus hasseltii) is found through-
The toxins generally behave like chemical agents and out Australia but more commonly in temperate regions.
serve the same function: to poison people. 147,148 Biologi- Tasmania has the lowest incidence, while areas around
151
cal agents are relatively inexpensive to produce and have Alice Springs, Perth and Brisbane are especially infested.
the potential to be devastating in their effects. Organisms The redback spider is easily identifiable by the presence
such as anthrax, plague and smallpox have been the of a red, orange or brownish stripe on its characteristic
agents of greatest concern from terrorists’ potential use. 146 black, globular abdomen. The female is much larger than
Biological agents have the longest history of use, having the male; generally only the female is considered danger-
been available for centuries. 148 ous. Juveniles are smaller, more variably coloured, and
may lack any spots or stripes. Bites from both male and
juvenile spiders may result in symptoms, although these
Radiological Materials tend to be less significant than bites from a female. 152
Radiological materials pose both acute and long-term The redback spider has also become established outside
hazards to humans. Action is similar to some chemical Australia, including in New Zealand and Japan. 152,153
agents: cellular damage. A major difference is that the Although bites are rare, small populations of redback
radiological agents do not have to be inhaled or in skin spiders have been reported in Central Otago (South
contact to exert damage. 145 Deployment of a nuclear Island) and New Plymouth (North Island) since the early
weapon would be catastrophic; note evidence of events 1980s. 153 The only other venomous spider in New Zealand
like Hiroshima and Chernobyl. While very different, both is the Katipo (Latrodectus katipo) from the same genus as
events produced immediate injury and the long-term the redback. The katipo has a black, rounded body,
effects of ionising radiation on large populations. 146 Any slender legs and a red stripe on the abdomen. Adult males
radiological effects on human health from the 2011 and juveniles are black and white but are smaller than
tsunami in Japan and the subsequent damage to the females. The black katipo is a shy and non-aggressive
Fukushima nuclear reactors remains unclear at the time spider, found in coastal areas of New Zealand. They are
of writing. The event of most risk is likely to be a ‘dirty found in much of the North Island and on the South
bomb’ that combines conventional explosives with any Island as far south as Greymouth on the west coast and
available radioactive source. 146 Dunedin on the east coast. 154 Their habitat is generally
warm, sandy beaches and dunes, although environmen-
A CBR terrorism incident may or may not result in mass tal changes have resulted in increasingly scarce sightings
casualties and fatalities as intended. However, large and bites are rare. Symptoms of katipo spider bite are
numbers of psychological casualties are very likely and similar to those of the redback spider and where indi-
therefore, regardless of the effectiveness of the attack, and cated, redback antivenom is available to treat bites from
the number of people actually exposed to the agent, there both spiders in New Zealand.
will most likely be a mass casualty situation. 146 The psy-
chological implications of chemical and biological A redback spider bite is a frequent cause for ED presenta-
weapons may be worse than the physical ones. Chemical tions and the most clinically significant spider bite in
and biological weapons are weapons of terror; part of Australia. 152,155 Most bites are minor, with either minimal
their purpose is to wreak destruction via psychological or no symptoms and requiring no antivenom. In approxi-
means by inducing fear, confusion, and uncertainty in mately 20% of cases, significant envenomation occurs
150
everyday life. The long term social and psychological and antivenom administration is generally indicated,
effects of an episode of chemical or biological attack, real although death is extremely unlikely in untreated cases. 156
or suspected, would therefore be as damaging as the acute Redback antivenom is the most commonly administered
effects, if not more so. antivenom in Australia. 152