Chapter 78 Biochemical terrorism

Biochemical terrorism is defined as the use of biological or chemical agents to intimidate, incapacitate or eradicate crops, livestock, civilian and military personnel.¹ It is well suited for attack by poorer nations against the rich, and is known as a poor man’s atom bomb, or asymmetric method of attack. The large scale use of mustard and nerve gases in the Iran/Iraq war,² the dissemination of nerve gas sarin on the Tokyo underground,³ and the discovery by UN inspectors in Iraq of SCUD missiles, rockets and aerial bombs primed with Botulinum and aflatoxins^4,⁵ have highlighted the need for planning.

CHARACTERISTICS OF BIOLOGICAL WEAPONS (TableS 78.1 and 78.2)

Intended target effects are due either to infection with disease-causing micro-organisms and other replicative entities, including viruses, fungi and prions, or to the toxins they elaborate. Their effects depend on the ability to multiply in the person, animal or plant attacked.⁶ Sequelae depend on host factors (state of nutrition, immunocompetence) and environment (sanitation, temperature, humidity, water quality, population density).⁷

Table 78.1 Potential weapons

Biological diseases	Chemical agents
Bacillus anthracis (anthrax)	Blisters/vesicants
Clostridium botulinum toxin (botulism)	Distilled mustard (HD)
Yersinia pestis (plague)	Lewsite (L)
Variola major (smallpox)	Mustard gas (H)
Francisella tularensis (tularaemia)	Nitrogen mustard (HN-2)
Viral haemorrhagic fever	Phosgene oxime (CX)
Coxiella burnetii (Q fever)	Blood
Brucella melitensis (brucellosis)	Arsine (SA)
Burkholderia mallei (glanders)	Cyanogen chloride (CK)
Ricin toxin (Ricinus communis – castor beans)	Hydrogen chloride
Staphylococcus enterotoxin B	Hydrogen cyanide (AC)
Niaph virus	Choking/pulmonary damage
Hantaviruses	Chlorine (CL)
	Nitrogen oxide (NO)
	Phosgene (CG)
	Nerve
	Sarin (GF)
	Soman (GD)
	Tabun (GA)
	VX
	Incapacitating
	LSD
	Cannabinoids

Table 78.2 Criteria for a successful biological weapon ⁶

CLASSIFICATION

Although classification of biological weapons can be taxonomy based (e.g. bacterial/viral/fungal), it is also useful to examine particular features such as:

• Infectivity: proportion of persons exposed to a given dose that become infected. This reflects the capability of an agent to enter, survive and replicate

• Virulence: ratio of the number of clinical cases to the number of infected hosts. May differ for strains of the same pathogen.

• Lethality: ability of agent to cause death in an infected population

• Pathogenicity: ratio of number of clinical cases to the number of exposed persons, which reflects the capability of an agent to cause disease

• Incubation period: time elapsing between exposure to the agent and first signs and symptoms of disease

• Contagiousness: number of secondary cases following exposure to a primary case in relation to the total number exposed

• Stability: ability of an agent to survive the environment

Another useful classification system available is that from the Centers for Disease Control and Prevention (CDC) Atlanta:

CATEGORY A

High-priority agents include organisms that pose a risk to national security because they can be easily disseminated or transmitted from person to person. They result in high mortality rates and have the potential for major public health impact, which might cause public panic and social disruption, and require special action for public health preparedness. Examples include anthrax, botulism, plague, smallpox, tularaemia and viral haemorrhagic fevers.

CATEGORY B

Second highest priority agents include those that are moderately easy to disseminate. They result in moderate morbidity rates and low mortality rates, and require specific enhancements of CDC’s diagnostic capacity and enhanced disease surveillance. Examples include brucellosis, salmonella, glanders, melioidosis, psittacosis, Q fever, ricin toxin, typhus, staphylococcal enterotoxin B and viral encephalitis.

ROUTES OF DISSEMINATION

• Inhalational exposure using sprays or aerosols: Optimal particle size for alveolar deposition is 0.6–5 microns. Particles larger than this are filtered by the nose, and smaller particles are exhaled. This can be achieved using aerosol generators mounted on stationary objects or primed onto trucks, cars, boats, cruise missiles and planes. Environmental factors such as wind velocity, cloud cover, rainfall and humidity affect the efficiency of dissemination.⁷

• Cutaneous: Via wounds and mucous membranes.

• Ingestion via food and water: Hand to mouth contact is a suitable vehicle, for example the Rajneeshee cult successfully disseminated Salmonella via salads, infecting 750 people in 1984.

SPECIFIC AGENTS

ANTHRAX

Anthrax ⁸ is an acute infectious zoonosis caused by Bacillus anthracis, a Gram-positive, spore-forming bacillus. The infective dose is 8000–50 000 spores and routes of transmission include inhalation, ingestion and skin contact. Person-to-person transmission does not occur for the pulmonary form but secondary cutaneous lesions may occur after direct exposure to vesicle secretions. As spraying by aircraft is a potential threat to a large city, pulmonary exposure is the most likely route in a mass casualty situation.