The Importance of Detecting Low-Level Bed Bug Activity

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Detecting bed bugs during the end of an eradication effort, just before they’ve been eliminated, is more difficult than it is at the onset of an infestation. This is especially true when relying solely on visual inspections, one researcher says.

December 13, 2016
Jordan Fox
Jeremy Scott Goins of Pesky Critters inspecting a BlackOut bed bug detector.

Renowned bed bug expert Dr. Richard Cooper believes the ability to detect low-level bed bug activity is key in accomplishing early detection. “The longer an infestation goes undetected, the more difficult and costly elimination becomes. And the more likely it is to spread to other apartments in housing communities, and out into society,” he says.

“Detecting low-level activity is also essential in guiding treatment efforts to determine when an infestation has been eliminated,” he adds. “Our industry relies on detection efforts to identify infestations, but doesn’t necessarily evaluate them enough to determine when, in fact, they’ve been eradicated.”

RECENT FIELD RESEARCH. During a recent bed bug webinar presented by PCT, Cooper, research entomologist and vice president of Cooper Pest Solutions and BedBug Central, Lawrenceville, N.J., discussed his recent research findings that can be applied when developing and implementing a sustainable IPM program in affordable housing. He also shared results that provided new insights on bed bug behavioral ecology.

Cooper listed four common detection methods used by PMPs and discussed the pros and cons of each.

INTERVIEWING RESIDENTS. “A verbal interview with residents can provide very useful information in just a few minutes, e.g., when and how bed bugs were introduced and how long were they aware of the problem. The interview also is an opportunity to educate residents about what they can do to help eradicate the problem — and some of the things they shouldn’t be doing. But interviews are often unreliable. Some residents may not even know they have an infestation, and some may be aware but aren’t reporting it to property management,” he said.

“The failure to report an infestation can be a huge problem. It could involve residents who are engaging in suspicious activities and don’t want people to know what they’re doing. In some cases, some residents may fear negative repercussions from property management,” Cooper added. “And some are simply embarrassed, not reporting the bed bug activity until things get so bad they can’t take it anymore. We see that most often in elderly communities where the residents fear the social stigma they experienced as children.”

Cooper’s research found about 60 percent of residents living in infested dwellings were completely unaware of the problem. “That’s why we see such high infestation rates in apartments for the elderly — and what’s really unbelievable is the severity of some of these infestations. (It’s) hard to believe that people will live under this condition without reporting the problem.”

CONDUCTING VISUAL INSPECTIONS. Visual detection is by far the most common detection method. “It’s advantageous in that it provides immediate results, but those results are limited by what can be observed at the time of the inspection. Also, visual inspections are labor intensive and tend to be less reliable for detection of low-level infestations,” he said.

SCENT DETECTION DOGS. K9 scent detection is increasingly popular, he said. “It’s very efficient, can overcome limitations of visual inspections, and provide immediate results in a single visit. It’s also very well suited for large-scale inspections, particularly in non-traditional environments such as office buildings, schools, movie theaters and retail stores — places where visual detection and detection devices may not be effective or economically practical. But one big disadvantage is it could produce a false positive alert — where a dog erroneously indicates presence of bed bugs.”

PLACING MONITORS OR TRAPS. Cooper’s research shows that the placement of interceptor traps has been the most effective of the four methods, particularly at detecting low-level bed bug activity.

Cooper Pest Solutions technician Terry Rice and Jorge Deleon of Preventive Pest, Houston.

“In one study of ours at an affordable housing unit with 358 apartments, 71 of them had bed bug activity at mixed infestation levels ranging from low-level to severe,” he said. “Based on resident interviews, only 30 percent had indicated awareness of activity. So the majority of those infestations would have been missed if we were just relying on the word of the residents. Our visual inspection detection rate increased to 69 percent; and placing interceptor traps under the legs of beds and upholstered furniture for a two-week period we detected 96 percent of the bed bugs in the apartments.”

In another study, Cooper’s team compared visual inspection to interceptor traps in 77 apartments with low-level infestations. “Here, the interceptor traps beneath the legs of the furniture detected 90 percent of the infestations, compared to visual inspections, which decreased to only 52 percent, compared to the nearly 70 percent when we were studying the more than 70 infested units with mixed levels.” So, he concluded, “The smaller the infestation level, the less reliable visual inspection is going to be.”

In yet another study, Cooper evaluated the ability of bed bug-detecting dogs to detect infestations and found a “great degree” of variability in results. “We examined 11 different handler-dog teams that inspected 276 apartments, 67 of which had bed bug activity. These teams had a mean detection rate of 44 percent, with some teams detecting as low as 10 percent, and another team up to 80 percent. We found a mean false positive rate of 14 percent, which ranged from no false positives with one team, up to 57 percent with another team.

“Teams that were evaluated on multiple days were inconsistent from one day to the next. When we compared that result to placing interceptors in the apartments, our interceptors detected 90 percent of the apartments over a two-week period.”

BEHAVIORAL ECOLOGY. Of all the detection methods, interceptor traps proved to most reliable, particularly for low-level infestations, he said. For this reason, much of his research focused on pitfall traps, which he used to study the behavioral ecology of bed bugs in field conditions.

“Originally, interceptor traps were designed to go under the legs of beds and furniture, but as you know not everyone sleeps in beds, and some bed frames can’t accommodate the interceptors beneath the legs. One of the things we learned was the fact that these traps are also very effective at capturing bed bugs as they travel away from sleeping and resting areas. So you can place them throughout apartments in various places where you wouldn’t typically find bed bugs, such as hallways, kitchens, entry doors and bathrooms.”

CLASSIC BED BUG DISTRIBUTION. Cooper said the classic bed bug distribution model suggests that 90 percent or more of these insects are found at sleeping or resting areas, such as beds and upholstered furniture, and only a small percentage of them are found in other areas away from hosts.

Bed bugs often are discovered in cracks and crevices of a sofa.

“But it’s important to understand that this is based upon the results of visual inspections, so these numbers are possibly skewed. It’s a lot easier to find bed bugs in beds or furniture, compared to finding them in areas that are difficult to visually inspect. And it turns out using interceptor traps throughout an apartment shows that bed bugs are much more mobile then previously believed. We found in one apartment that 63 percent of all bed bugs were captured in interceptors that were located throughout the apartment in addition to the sleeping and resting areas.” Thus, the classic distribution model best reflects bed bug resting areas and not necessarily bed bug movement.

In discussing the stages of the bed bugs captured in interceptor traps placed throughout apartments, he revealed that of the 15,000 bed bugs captured in 77 apartments, the majority were immatures and only 13 percent were adults. “Of the immatures, the vast majority, 82 percent, were small nymphs — first or second instars — and only close to 20 percent were larger stages. This is important because these young nymphs are very small and can readily escape visual detection.

VISUAL DETECTION CHALLENGES. “Detection of bed bugs during the terminal end of an eradication effort, just before they’ve been eliminated, is more difficult than it is at the onset of an infestation. This is especially true when relying on visual inspection to determine if they’ve been eliminated — which is what most PMPs are doing — and that can be wrong and/or dangerous.”

In a small case study Cooper conducted of five apartments that were being treated, one bed bug was detected in one of the five apartments during a visual inspection, he said. “So it would be easy to conclude that the infestation had been eliminated in the other four apartments where bed bugs had not been visually observed. But when interceptor devices were placed beneath the legs of the beds, we detected bed bugs in three of the five apartments.

“What’s really interesting is when we placed interceptors away from the sleeping areas throughout these apartments, we found bed bugs in all five, and the numbers we detected were quite large,” he said. “So in fact all five apartments were still infested.”

The important point Cooper stressed was that based on the visual inspections alone, it could have easily been concluded that the problem was resolved in four of the five apartments. “But with the traps, we saw that the bed bugs hadn’t been eliminated in any of them. It’s easy to see how treatment efforts that are prematurely terminated could possibly promote a bed bug population rebound, or further spread of bed bugs to other apartments.”

The author has been writing about the pest management industry for more than 30 years. Email him at jfox@gie.net.