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Insects: tougher than anthrax

The ruins of the yellow-rat breeding room at Japan's notorious germ warfare center, Unit 731, in China.
The ruins of the yellow-rat breeding room at Japan's notorious germ warfare center, Unit 731, in China. (Corbis)

MICROSCOPIC AGENTS SUCH AS smallpox, ebola, and anthrax have become synonymous with bioterrorism. But insects can be more practical and effective.

Producing sufficient quantities of viruses or bacteria can be technically challenging, the process is extremely hazardous, and it is difficult to find a way to disperse the product effectively. Getting particles of the right size to stay aloft as an aerosol is not simple, and if the winds shift an otherwise effective attack is neutralized.

Anthrax, for example, is easy to isolate and can be milled into a light powder, but it doesn't replicate quickly and it doesn't pass readily between people. In the anthrax attacks via the US mail system in 2001, seven letters with up to a gram of highly refined, nearly pure spores yielded five deaths, and none of the infected people passed the disease on to others. The attack caused enormous disruption, but the mail bombs sent by Ted Kaczynski were nearly as lethal.

Insects, on the other hand, often can be gathered in sufficient numbers to seed an outbreak. Their eggs are environmentally robust and small enough to carry by the thousands without risk of detection. A single Medfly female in a survey trap is enough to immediately shut down an agricultural exporter, and finding two flies within a 1-mile radius triggers an eradication program.

Microscopic agents are typically highly vulnerable to ultraviolet radiation, desiccation, and heat, and lack the ability to seek out hosts. But insects can withstand adverse conditions and have evolved elegant sensory systems and incredible flight mechanisms that allow them to locate their hosts.

A decent representative of the technological level of today's terrorist is the Japanese biological warfare program in World War II. After seven years of work with microbes, the only people killed in the first attack with bacterial weapons were 40 Japanese who launched the assault and became accidentally infected with typhoid. So the Japanese turned to insect-borne diseases. A year later they killed 50,000 of their enemy in the first attack with plague-infected fleas.

-- J.L.

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