Beagle vs. bedbug: The hunt is on

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Calls to pest-control professionals for bedbug infestations have increased 100-fold in the United States in recent years, experts say. The common bedbug, Cimex lectularius Linnaeus, has been feeding on the blood of sleeping humans for more than 3,500 years, but it was eradicated during the 1930s in the United States with the use of dichlorodiphenyltrichloroethane (DDT). Since the 1990s, about two decades after DDT was made illegal because of its adverse effects on the environment, the pests have made a resurgence in American homes, apartments and hotels. The resurgence is primarily due to people traveling more, the increased trade in secondhand furniture, and resistance of bedbugs to available pesticides, experts say.

Bedbugs hide in cracks and crevices during the day and leave their harborages to feed at night, especially attacking sleeping humans. Their cryptic nature makes small infestations hard to detect, especially by visual inspection. Eventually an infesta tion can reach significant numbers, especially in low-income areas where limited income is available to deal with infestations, or in hotels and apartments that may have growing levels of infestation before they're detected.

The U.S. Centers for Disease Control and Environmental Protection Agency consider bedbugs a pest “significant of public health importance” and an emerging public health problem.1

Bedbugs require human blood as part of their life cycle, necessary for molting from nymph to adult. Their bites can create an immune response ranging from a minor irritating rash to severe allergic hypersensitivity. Heavy infestation can result in anemia. Though human laboratory results have not shown bedbugs to be vectors of viral, bacterial or protozoal pathogens, some health researchers suspect they might be capable of transmitting hepatitis B virus and antibiotic-resistant bacteria.

Brody, a bedbug-sniffing beagle, alerts-gives a positive indication that he's found bedbugs or their eggs-in a hotel room. Photo courtesy of Rick Cooper, PhD.

Impressive results of a controlled study

Because dogs don't rely only on visual cues, their enhanced olfactory ability has propelled their use in bedbug detection. In a series of studies by Margie (Pfiester) Lehnert at the University of Florida, properly trained dogs were shown to be extremely accurate at bedbug detection, indicating on as few as one male or female bedbug and as few as five viable eggs.

The researchers used a modified food- and verbal-reward training system with dogs who worked with individual scent-detection stations. The dogs were shown to have a 97.5 percent positive indication rate and no false positives. They also were able to discriminate live bedbugs and viable bedbug eggs from dead bedbugs, cast skins and feces. In a controlled experiment in hotel rooms, dogs were shown to be 98 percent accurate in locating live bedbugs.2

“Breed selection was left up to the trainers, but we know that one of their main criteria was selecting smaller dogs that would be less of a burden when working in a home,” Lehnert says. The trainers used beagles, Jack Russell terriers and other smaller breeds with the appropriate temperament, personality, assertive work tendency and scent drive. Most of the dogs were rescued from shelters.

Lehnert and her colleagues also showed that dogs were able to distinguish live bedbugs from other household pests, including carpenter ants, cockroaches and termites. Furthermore, dogs trained to locate the scent of live bedbugs in experimental scent-detection stations were able to shift that ability to a more realistic hotel room situation.2

But what about the real world?

So are bedbug detection dogs as effective in natural field conditions? Rick Cooper, PhD, technical director of Cooper Pest Solutions in Lawrenceville, New Jersey, and co-owner of BedBug Central, set out to answer that question. He and his research colleagues at Rutgers University studied the ability of 11 dog handler–bedbug-detection teams to detect bedbug infestations under natural field settings.3 The experiments were as follows:

• Experiment 1: Blind evaluation in preselected apartments.

• Experiment 2:  Informed inspection of preselected apartments.

• Experiment 3: Informed building-wide inspection.

The results? Cooper's dog-handler teams were far less successful than those studied by Lehnert. There was great variation among the teams, and the percentage of efficacy was markedly reduced. In three distinct settings, the mean effectiveness of the 11 dog teams studied was 44 percent, with a mean false-positive rate of approximately 15 percent, though the companies involved promoted their dogs' accuracy as greater than 95 percent.

The results of experiment 1 showed that dog-handler teams accurately detected bedbugs 47 percent of the time, with 19 percent false positives. In experiment 2, the time for a team to inspect an apartment was 5.3 minutes. The team with the highest detection rate (77 percent) also had the highest false positive rate (57 percent). The team with the lowest detection rate (15 percent) had the lowest false positive rate (14 percent). In experiment 3, the mean inspection time per apartment was 1.2 and 4 minutes for the two canine teams. The detection and false positive rates were 22 percent and 8 percent, and 43 percent and 5 percent, respectively. In experiment 4, the two canine teams detected 83 percent of live hides and falsely alerted-gave a positive signal that bedbugs were present-on 25 percent.

Cooper says he and his fellow researchers are still trying to understand why the results of the dog-handler teams in the field were so much lower than those in the controlled training environment of Lenhert and colleagues. A followup study to try to determine the cause failed to receive funding, he notes.

A bedbug dog checks out a printer in an office building. Photo courtesy of Jose “Pepe” Peruyero, High Springs, Florida.

Handler experience makes the difference

Based on the known capability of dogs' olfactory system to detect a variety of substances-from cancer to explosives-one would expect them to be highly effective in detecting bedbugs in a variety of environments, as long as the handlers know how to assist them. And that's Cooper's explanation for the teams' poor performance: handler inexperience.

“If you look at Pfiester's study, their dogs were very well-trained, the handlers provided by the training facility were highly skilled, and the study was done in a very simple, controlled environment: a hotel room,” he says. “The Pfiester study clearly demonstrated the ability of the dogs to detect bedbugs at a very high degree of accuracy if you have a properly trained dog and a highly skilled handler.”

He says many companies in the bedbug detection business don't have previous experience working with dogs and may not be as committed to the continued maintenance training and handling as those who handle bedbug-sniffing dogs for a living.

Cooper was certified as a bedbug dog handler several years ago. “I was given a trained dog and went through three to five days of basic bedbug dog handling, and a certification exam in a controlled environment,” he says. “I would imagine that's what many of these companies' dog handlers did, too.”

4 questions to ask when buying or leasing a bedbug dog

If your veterinary clients-or you-are curious about employing the olfactory services of a bedbug detection dog, here are some things to check.

1. Is the dog's training up to date?

Most training is performed using proven apparatus, but it is also important that dogs be trained in the field. The dog should be inspection-ready at the time of service-in other words, it should be able to go into a house or hotel room on the first day and be qualified to do the inspection. The dog's work routine should be programmed during the training process, not afterwards.

2. Can the dog differentiate between live bedbugs and old evidence of infestation?

It's important that dogs don't alert in the absence of live bugs and eggs on old evidence.

3. Can the dogs detect bedbug eggs?

The earliest stages of an infestation may be limited to just a few eggs. The ability of a dog to alert to eggs when there are no other stages present is the highest level of detection possible. Such accuracy enhances confidence in declaring that a treated infestation probably has been eliminated.

4. Are reliability claims backed by evidence?

You may hear trainers and dog handlers claim that their dogs are 97 percent accurate. Ask for the data that back up their claims.

Source: Cooper, R. Four-Legged Bedbug Detectors. Pest Control Technology 35(8):76-78.

It's not that the handlers don't try, he reiterates. “It's that they're only as good as they're capable of with the minimal training they receive. If the handlers don't keep their dogs maintained at a high level of ability, or their handling experience is not to the degree it should be, that might account for the poor results we encountered.”

Public confidence at stake

The concern is whether the public can be confident in such bedbug pest control services. Cooper believes more research is needed.

“If I were contracting for canine bedbug scent detection and a dog gave an alert, I would want that alert confirmed by visual inspection or monitor detection. At this point I do not have the confidence to trust the handler-dog teams,” he says. “It's one thing to work with a dog in a controlled environment, but the real world is much more complex. Unfortunately, our study found that there are some problems.”

In his Bedbug Handbook: The Complete Guide to Bedbugs and Their Control,4 Cooper offers some conclusions. “The more bedbug detection tools you can deploy, the more likely you are to detect infestations early when bedbugs are the easiest to control,” he writes. “Canine scent detection offers the only practical method for large-scale inspections in non-residential settings, such as schools, office buildings, retail stores, theaters, or mass transit, where thousands of square meters may require inspection and where bedbugs are less predictable, making them more difficult to detect by other methods.”

Depending on handler expertise, bedbug dogs can locate the pests with up to 98 percent accuracy. Photo courtesy of Jose “Pepe” Peruyero, High Springs, Florida.Lehnert says she's glad Cooper did his study, because it showed the difference between a controlled experiment and the real world. “Cooper's study was pivotal to show the reality of bedbug detection in natural settings,” she says. “Our study was done to show the possibility of training a dog to locate bedbugs, and the accuracy of trained dogs to differentiate live bedbugs and viable bedbug eggs, both a sign of an active infestation, from dead bedbugs.”

She agrees with Cooper that the variance between her study and his is human error, not the dogs' capabilities.

“Bedbug-detecting dogs are exceptional at what they do-their olfactory capability is so great,” she says. “One dog we worked with was capable of locating on the scent of the bedbugs with 100 percent accuracy, without ever entering the room, just from the airflow seeping out from below the door. The room was later shown to have only five live bedbugs in it.”

References

1. Vaidyanathan R, Feldlaufer MF. Bedbug detection: Current technologies and future directions. Am J Trop Med Hyg 2013;88(4):619.

2. Pfiester M, Koehler PC, Pereira RM. Ability of bedbug-detecting canines to locate live bedbugs and viable bedbug eggs. J Econ Entomol 2008;101(4):1389.

3. Cooper R, Wang C, Singh N. Accuracy of trained canines for detecting bedbugs (Hemiptera cimicidae). J Econ Entomol 2014;107(6):2171.

4. Pinto LJ, Cooper R, Kraft SK. Bedbug handbook: The complete guide to bedbugs and their control (Mechanicsville, MD: Pinto & Associates, 2007).

Suggested Reading

1. Brooks SE, Oi FM, Koehler PG. The ability of canine termite detectors to locate live termites and discriminate them from non-termite material. J Econ Entomol 2003;96:1259.

2. Lenhert MP, Weeks ENI Weeks. Canine olfaction science and law: Advances in forensic science, medicine, conservation, and environmental remediation. (Boca Raton, FL: CRC Press, available March 2016).

3. Cooper R. Are bedbug dogs up to snuff? Pest Control 2007;75(1):49-51.

Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.