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Bed bugs

Bedbugs are on the rise, but researchers at the University of Minnesota are working to keep them from infesting hotels and our homes.

Bloodthirsty travelers: Bedbugs are biting again

By Jennifer Amie

From eNews, Oct. 12, 2006

In his St. Paul campus lab, assistant professor of entomology Stephen Kells rolls up his sleeve and picks up tweezers. He opens a covered glass Petri dish and removes a single bedbug--reddish-brown, shaped like a sesame seed, and exceedingly flat--and places it on his arm. The pointed tip of its abdomen is black with blood from a previous meal, but the creature is clearly hungry. In an instant, it has plunged its proboscis into Kells, and soon its transparent body darkens as Kells' blood trickles in.

As the insect swells with its meal, it elongates and changes shape. Once as flat as a sheet of paper, it becomes swollen and plump. Within five minutes it is satiated and begins to crawl away, only to be snatched again by Kells and returned to its dish.

The bedbug's natural habitat is the human bedroom or hotel, where it feeds at night while its host is sleeping. Bedbugs are normally hidden by day, and because many people show no reaction to their bites--no telltale bump or rash--the first sign of an infestation is often clusters of dark spots (fecal specks) on the sheets and mattress where the bugs hide during the day.

In generations past, bedbugs were a familiar fact of life. Our long, interconnected history with the insects dates to prehistoric times when bedbugs, which originally evolved as parasites on bats, switched hosts and began to feed on our cave-dwelling ancestors. When humans developed an agrarian society, bedbugs moved with us from cave to hut--and they've dogged our steps ever since.

University of California entomologist Robert Usinger has traced literary references to bedbugs back to Aristophanes and Aristotle, and noted that physicians, dating back to the time of Nero, once used the bloodletting bugs to treat snakebite and malaria. Bedbugs have long been associated with the unsanitary conditions of war, plaguing soldiers in the American civil war and World War II.

Humans enjoyed a brief respite from these parasites during the years when long-acting pesticides, such as DDT, were in widespread use. "They became a biological oddity over the last 30 years," says Kells. "We have a whole generation of entomologists who have never seen a live bedbug."

Sleep tight and don't let the bedbugs bite

That old adage might be coming back into our jargon. Listen to an interview about bedbugs with Stephen Kells, assistant professor of entomology, on the University of Minnesota Moment.

That, however, is about to change. Since 1999, says Kells, bedbug infestations have been on the rise in North American hotels and homes, including some in the Twin Cities. A grueling--and expensive--regimen of steam cleaning, vacuuming, and insecticide application awaits anyone unlucky enough to fall victim to an infestation.

Other factors have encouraged the insects' recent resurgence, including the prevalence of international travel and the lack of public awareness. Today, bedbugs travel worldwide on jets--hitchhiking on people, clothing, and suitcases--and check into even the nicest resorts.

Kells was working in the pest control industry when bedbugs once again became a major problem in North America, about six years ago. While investigating ways to eliminate hotel infestations, he noticed a curious phenomenon: While most bedbugs cluster (in groups ranging from tens to hundreds and sometimes thousands) in hidden crannies surrounding a bed, a handful of wanderers can often be found in more distant locations, such as an air vent or other remote nook.

Why, Kells wondered, do these outlying bugs stray far from their food source? Perhaps they are seeking a place of safety, dispersing to find a new host, or leaving an infestation that has grown too large. In any case, the behavior has direct implications for pest control--especially if the "outliers" are laying eggs.

Stephen Kells
Bedbug expert Stephen Kells

"If you get rid of 95 percent of them around the bed, but 5 percent have gone elsewhere, you have to look for them," says Kells. "In a hotel with multiple units, you would want to know whether they are going to other rooms, and at what rate. Ideally, you want to know what triggers them to move on."

One possible trigger is the release of an alarm pheromone. Bedbugs, like many insects, communicate via scent, releasing a sickly sweet odor when squashed or injured. It's possible that the far-flung bedbugs are fleeing in response to this chemical distress signal.

Kells is fortunate to have two colonies of live bedbugs available for scientific testing of this premise. One colony comprises bugs gathered recently from the field. The other was inherited from U.S. military researchers who kept it alive for more than 50 years even though, during that time, bedbugs were virtually unheard of in the United States. Their foresight has been a boon for Kells' research. Both colonies are kept alive in secure conditions within a laboratory growth chamber. The 75 vials of insects are fed twice a week--not on Kells, but on human blood heated to body temperature and dispensed through an artificial membrane.

Tips for travelers: How to avoid bedbugs

"The greatest risk for encountering bedbugs appears to be while people are traveling," says U entomologist Stephen Kells. "Regardless of the type of accommodations, it is a good precaution to check your room. Look around the headboard and adjacent area of the bed. Also inspect luggage stands or other areas where suitcases are typically set down. Be aware of any unexplained bites you may find in the morning; that could be the result of bedbugs. Also watch for fecal spots, which could occur on bed sheets or nearby areas. Inspect your luggage when you get home after a trip for any bedbugs that may have escaped your earlier attention."

Through a series of laboratory experiments, Kells hopes to shed light on what stops certain bedbugs from being attracted to a site. Using sophisticated equipment, he can measure the bugs' neural response to the alarm pheromone or other chemical signals. Future behavioral studies could document the bugs' reactions to pheromones or other stimuli.

Kells hopes his research will contribute to humans' longstanding efforts to keep bedbugs at bay. "It's a societal problem and a significant public health concern," he says. "We are going to continue to have a long, interconnected history with this bug. I'm not sure how far this initial resurgence will spread, but eventually we'll probably get some sort of control over them, with the problem rearing its ugly head every once in a while. But in places that do not have the resources to control bedbugs, people are going to continue to live with them."