Biological Hazards

Sometimes it seems almost too dangerous outdoors to be a groundskeeper. As if rattlesnakes, honeybees and Lyme disease weren't enough to deal with, over the years several new introduced hazards have arrived to threaten Americans working outside. All are killers.

The three major new threats to grounds maintenance workers — killer bees, West Nile virus and fire ants — are spreading. But in reality, although danger exists, these new threats are not always as large as the media projects. And for various reasons, some may become less dangerous over time.


The most dangerous of the imports is the Africanized honeybee, commonly known as the killer bee. Its reputation is well deserved, as swarms have killed hundreds of people and uncounted animals in South and Central America since their escape from a Brazilian research facility in 1959.

Resembling the European honeybee to the naked eye, killer bees reached Texas in 1990. According to the National Agricultural Pest Information System, they are now safely ensconced in the United States, and they are progressing northward.

Killer bees are much more aggressive in defending their hives than domesticated European bees, and news reports of attacks are terrifying. An Arizona man was stung by 1,000 bees and killed after he pushed his lawnmower over a colony. Several deaths have occurred in the U.S., five in Arizona alone. The bees attack in numbers high enough to kill a horse — which happened recently in southern Nevada.

“Africanized bees are such a contrast with European ones,” says Dr. Gloria DeGrandi-Hoffman, of the USDA Carl Hayden Bee Research Center in Tucson, Ariz. “Their nest behavior has a lower threshold. It will trigger much more activity than European bees.”

The killer bee is more dangerous because it swarms more aggressively and for a longer period of time. Thus, someone caught working outdoors with no shelter is vulnerable. If a hive or swarm is disturbed, or even approached closely, thousands of bees will attack relentlessly. A sting pheromone is released, attracting even more bees to the target.

According to the Bee Research Center, the best defense is to cover your face and head as much as possible and run like crazy for the nearest sanctuary, such as a vehicle or house. Do not jump into water because the bees will wait for you to come up for air.

“If you have been stung more than 15 times, or are feeling ill, or if you have any reason to believe you may be allergic to bee stings, seek medical attention immediately,” says DeGrandi-Hoffman. “The average person can safely tolerate 10 stings per pound of body weight. This means that although 500 stings can kill a child, the average adult could withstand more than 1,100 stings.” Stingers should be removed not with tweezers, which can plunge more venom into the victim, but scraped off.

One danger to grounds maintenance workers is that a killer bee colony can occupy a very small space. Nests can be in water meter boxes, metal utility poles, cement blocks, as well as holes in the ground, house eaves or tree limbs. They often attack when disturbed by noise or vibrations, as from mowing equipment.

Killer bees are currently established in most of Texas, all of Arizona and in southern New Mexico and California. They have been found in Nevada, Florida, Alabama, South Carolina and Virginia.

DeGrandi-Hoffman says, however, that the danger from killer bees will ultimately diminish. The northward spread has slowed, and there is a concerted effort both in the United States and in Mexico to breed the aggressiveness out of them.


“Outdoor workers are the ones most likely to get West Nile Virus (WNV),” says Emi Saito of the USGS National Wildlife Health Center. They become infected when bitten by a mosquito carrying the virus. Mosquitoes become infected when they feed on bird blood that has high levels of WNV.

According to the Center for Disease Control (CDC), the virus first appeared in North America in 1999. It has spread rapidly since then. By January 2004, cases were reported in every state except Oregon, Washington and Alaska. WNV is a particular threat to outdoor workers because it usually flares up in the summer and continues into the fall. In 2002, however, cases were still being reported as late as mid-December.

“The vast majority of people infected with WNV never know it,” says Saito. According to the CDC, fewer than 20 percent develop any symptoms at all. Most of the others come down with fever, headache, body aches, skin rash, nausea, and vomiting or swollen lymph glands. These symptoms usually appear between three and 14 days after they are bitten by an infected mosquito. They last a few days.

Less than one percent of people who are infected develop the more serious meningitis or encephalitis. Their symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, although the neurological effects may be permanent.

The CDC estimates that less than one out of every 1,000 infected people dies of the virus. There is no specific treatment or vaccine for WNV. In mild cases, symptoms go away on their own. People who are seriously ill with the virus should seek medical care as soon as possible.

To reduce your chances of being bitten by a mosquito, wear long pants and long-sleeved shirts when outdoors. Apply an insect repellent containing DEET to clothing and exposed skin. Try to stay inside as much as possible at dawn, dusk and in the early evening.

Reduce mosquito habitat by draining sources of standing water. Don't touch dead birds with your bare hands, and contact your local health department for instructions on reporting and disposing of them.

“We don't really know what the future holds for West Nile Virus,” says Saito. “It's out there and it's been maintained between birds and mosquitoes. It flares up and subsides.” The good news? Scientists report that WNV is likely to stabilize in the long term, because infected people build up an immunity to it.


Red imported fire ants are the other menace to outdoor workers, although their expansion has been much less dramatic than that of West Nile Virus. According to the USDA, they came to the United States from South America in 1929. They spread across the South following the planting of turf sod and woody ornamental plants.

Today, they can be found throughout the southeastern United States as far west as Texas, and as far north as Kansas and Maryland. Their introduction into California a few years ago was a huge cause for concern, and it is feared they will spread throughout the state's coastal and irrigated regions.

Fire ants are feared for their painful, burning stings. They sting ferociously to defend their colony and their food sources, and continue to sting even when they have no venom left. Within 24 to 48 hours a white pustule forms at site of the sting. These pustules can become infected and can leave permanent scars. If a person can't get away from them, they can die from the thousands of stings, according to Dr. Sanford Porter of the USDA Agricultural Research Service in Gainesville, Fla.

“The biggest problem is for the people who are allergic to them,” says Porter. About one percent of Americans are sensitive or allergic to stings of fire ants. That's half a million people in the southeastern United States alone. Reactions include general body swelling, chest pains, nausea and dizziness, up to anaphylactic shock and coma.

“We suspect a couple of people a year die of fire ants,” Porter says. If you're an outdoor worker and sensitive or allergic to red imported fire ant stings, you have two choices. Obtain desensitization shots or leave the industry. You should discuss getting these shots with a physician. You can't be a landscape worker without running into fire ants in areas they inhabit.

A study by the University of Arkansas at Monticello, Ark., and the USDA-ARS lab in Gainesville, Fla., predicts that fire ants will probably move 50-100 miles north in Oklahoma and Arkansas. They also likely will continue expanding into portions of Virginia, Maryland, and Delaware in the east and New Mexico, Arizona, Oregon, Nevada, and possibly even Washington and Utah in the west.

There is no way to control fire ants over large areas. Drenching their mounds with insecticides can be effective locally, as can fumigants. Ant bait works more slowly, but is generally safer, cheaper and more effective in the long run. Porter and others are working on imported biological controls, which hold the greatest promise.

Difficult to identify, fire ants are small (⅛ to ¼ inch) but can build mounds more than a yard wide for their nests. They also nest in places such as rotten logs, walls of buildings, as well as under sidewalks and roads. They are attracted to electrical currents and can damage electrical machinery like heat pumps and air conditioners.


According to scientists, killer bees will become less aggressive in time. Humans will become immune to West Nile Virus. But the fire ant sting may always be a hazard.

Don Dale and Janet Aird are freelance writers who reside in Altadena, Calif.

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