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Could Insects Be Used as Instruments of Biological Warfare? - 2003-01-29

Emergency workers across the United States have begun to receive smallpox vaccinations as U.S. authorities prepare for possible bioterror attacks. The use of deadly viruses as agents of destruction is not unheard of in war, and strategic planners are working to head off any threat. But would they notice, or could they stop, an attack carried out using insects? And is such an attack possible?

The use of insects as agents of warfare is not a new idea. In the Biblical story of the Exodus, one of the plagues visited upon the Egyptians was a horde of locusts. In a short-lived program in the mid-20th century, the U.S. Army reared 100 million yellow fever mosquitoes each week for possible use as a biological weapon against enemy troops.

"There are very few examples of where insects were used in the context of weapons of war, and there's almost no examples of where they were effective," Mr. Carey said.

James Carey, a professor of entomology at the University of California, Davis, is a specialist in what he calls 'invasion biology.' Although he doesn't consider the potential entomological threat to the United States to be as important as other forms of bioterrorism, he does see a way insects could be used as an economic weapon, targeted at American agriculture. Crop-destroying pests, he said, would be one likely form of attack.

"If you find what they call a 'Class-A pest' like the Mediterranean fruit fly and you have someone with a bottle full of Medflies deliberately planting them in traps, what happens is that it sets in motion the eradication campaign programs, the quarantines, because it's very difficult to distinguish between a real outbreak and one that's deliberately planted. So I can see that as the worst nightmare situation," he said.

The screwworm, which can devastate cattle herds, is also small enough to carry in a bottle and release onto a ranch, triggering an infestation that, if unchecked, could cause serious economic damage.

But according to Ian McDonnell, executive director of the North American Plant Protection Organization, there are myriad systems in place in the United States, as well as Canada and Mexico, that can identify, control and eradicate pests, no matter how they're introduced.

"We certainly rely on surveillance and the ability to rapidly identify the existence of a new pest and that's not restricted to governments. Producers, who are very well in tune with their crop, will be able to identify a new pest situation. We rely on universities and other academic institutions, scientific societies such as the Entomological Society of America, literature reports. So there's a vast array of sources that we count on to identify these new pest situations," Mr. McDonnell said.

In addition, the diversity of American agriculture makes it unlikely that an insect attack on a single commodity could have the catastrophic effect a terrorist group would probably be seeking. Still, entomologist James Carey says he would like to see closer collaboration between medical epidemiologists and invasion biologists in developing a national policy to prepare for pest outbreaks caused by such saboteurs.

"Clearly, you need a short-term program where you're always prepared for these outbreaks, but that's no different than preparing for naturally occurring outbreaks. I think one of the dangers here is for regulatory agencies to start seeing terrorist bogeymen all over the place and attribute these naturally occurring outbreaks to the terrorist planet and so forth," Mr. Carey said.

Yet, even as some entomologists discount the threat of insects being used as weapons, others are working to develop insects for military defense for example, wasps trained to become weapon detectors.

"One of the things we've learned is that wasps can be trained to detect numerous odors, and so you can train them to detect odors, like explosives and perform certain behaviors in response," says Jim Tumlinson who works for the USDA's Agricultural Research Service, in Gainesville, Florida. His work takes advantage of the wasps' natural feeding responses, such as rubbing their antennas on a spot with food or getting in position to sting their prey. Once the wasps learn to associate a particular odor with food, the scientists can watch for those feeding behaviors.

"One of the projects we were working on was to see if we could train wasps to locate explosives that might be in landmines. This project is not complete and there's still a long way to go to develop wasps as detectors of chemicals of various types. Certainly they have the ability to learn we haven't found a chemical yet that they couldn't learn," Mr. Tumlinson said.

Mr. Tumlinson predicts that trained wasps might one day also be used to detect dangerous food contaminants like salmonella and aflotoxin.

In this post 9-11 world, the U.S. government and the farming community are on high-alert to possible sabotage - aware that even in peacetime, they can expect insects will annually do billions of dollars in damage to the nation's crops and livestock. If terrorists try to cause similar damage with the deliberate release of a nasty agricultural pest, experts say chances are very good the outbreak would be quickly halted.