K-State Researchers Say Bug Zappers May Cause More Harm Than Good

The onset of summer brings a plethora of activities, including backyard cookouts. But also with summer comes an onslaught of pests such as flies and mosquitoes. Perhaps nothing ruins an outdoor barbecue more than the annoying presence of uninvited guests of the bug variety.

To battle these winged-nuisances, many people have installed or use an electrocuting insect trap or bug zapper. While the sizzling "zzzap" of the fly being fried -- or any other unfortunate insect lured to its jolting demise by this shocking siren -- may be music to the host's ears, the fly may ultimately have the last laugh -- especially if the devices are used around food handling areas.

According to a team of researchers at Kansas State University, that sound may also signal the potential for a shower of microorganisms including viruses cascading onto the surrounding area. Because of the airborne bacteria and virus-laden particles produced by the explosion of these electrocuted insects, the researchers recommend they not be used in food handling areas, hospitals, daycare facilities or any variety of places where the control of insects is important.

"The bug zapper is probably not the method of choice of killing insects because it might actually aggravate the situation, in terms of a microbial spread," said James Urban, a K-State associate professor of biology.

Urban conducted the study along with Alberto Broce, a professor of entomology; Kim Huntzinger, a recent K-State microbiology graduate; and Kent Hampton, an entomology research assistant. The result of their findings were presented Wednesday at the American Society for Microbiology's conference in Chicago.

"We're compounding the problem rather than solving it because the operation of these bug zappers results in the generation of high numbers of airborne insect particles," Broce said. "That presents an additional problem because we can breathe those particles, and it is well documented that insect particles can be very allergenic."

Despite the heat generated when the bugs are electrocuted, contamination on the fly's surface area or its digestive canals is not heated to a level lethal enough to destroy the bacteria and viruses. This allows them to survive on the particles ejected by the explosion. It is the heat that causes the bugs to explode.

According to the researchers, internally contaminated flies, or those that have bacteria and viruses in their digestive canals, are less likely to spread them because the microorganisms are on the inside of the fly. Urban said the increased distribution of organisms on the fly surface is potentially significant because the surface contamination is most likely to result from the flies moving about on filth such as feces.

Urban said although only about 1 in 10 million of the viruses in the fly's digestive canals are released upon electrocution, the released viruses and bacteria can be spread over a great distance.

"We were surprised to see as much microorganism dissemination as was the case," Urban said. "We thought there may be a few bacteria that got spread, but we're finding really significant amounts on the surface of the fly will survive.

"You can say 'well one in 10,000 is not very high,' except that flies will carry millions of bacteria naturally. If you're having one in 10,000 survive, that means hundreds literally can get spread from each fly during the explosion."

In addition to the harmful particles, Broce said the zappers only kill a small percentage of insects that are annoying or damaging to human health. They also indiscriminately kills "beneficial" insects that help control other bugs.

Broce said research indicates more often than not people are bitten by mosquitoes in the vicinity of the traps than away from them. The lights from the traps draw mosquitoes from large distances, and increase their density in the vicinity of the traps. Once in the vicinity of the traps the mosquitoes change course and direct their attention to nearby humans or animals.

"We jokingly say if you have problems with mosquitoes in your backyard, give one of these traps to your neighbors so the mosquitoes will go over there," Broce said.

According to Broce, manufacturers are moving away from using traps with electric grids. Newer traps capture and kill insects using an adhesive board behind a light to attract the insects. Broce said these models can be modified to be just as efficient as those with electric grids.