Those of us who deal with bed bug infestations know these insects use — as temporary or long-term harborages — the typically undisturbed seams, folds, crevices, recesses and cavities associated with bed components, furniture, wall hangings, interior structural components of residences, luggage, clothing, children’s comfort toys, book bindings, electronic devices and other personal property. Some bed bug harborages are readily treatable with appropriately labeled insecticides, a superheated (“dry”) steam or a jet of ultracold carbon dioxide (CO2). Others aren’t.
Sensitive electronic devices, art objects, books and other personal property don’t respond well to moisture, pesticide residues or extreme temperatures. Likewise, potentially infested clothing and comfort toys can be hot-laundered and hot-dried or dry cleaned, but this is an arduous task when all the clean hung and folded clothing in a bedroom and closet is considered. Heat treatment and fumigating residences are effective ways to eliminate bed bugs; however, these processes are costly and unaffordable to many families and individuals whose residences have become infested with bed bugs.
Using vacuum storage bags as a possible bed bug disinfesting method was presented to the structural pest management industry first in 2009 by Stoy Hedges1 at the 73rd Annual Purdue Pest Management Conference. He found the level of air removal achievable with a household vacuum cleaner from the vacuum storage bags alone was insufficient to kill the bed bugs he placed in the bags. Hedges suggested including an appropriate quantity of Ageless brand oxygen absorbers2 with the items placed in the vacuum storage bags to asphyxiate any bed bugs in the enclosed space. Ageless has been used for years to help protect bagged museum pieces from becoming infested by stored product pests and fabric pests.
Hedges also attempted to test the higher level of vacuum achieved with a food vacuum storage system on bed bug survival in various containers. Although the contained bed bugs died, the amount of air removed caused several plastic and glass containers to implode and break, rendering the process impractical.
The notion of using vacuum storage bags to disinfest clothing and other items has been suggested and disproved by bloggers on social media (BedBugger.com, for example). Still, I wanted to determine, to my own satisfaction, if this method had merit.
Study sample
The bed bugs I used in my study were from a population originating from live insects collected from several infested residences and assisted-care facilities in greater Columbus, Ohio. Bed bugs were fed on my arm every two to three weeks. The other components were:
- four StoreHouse brand vacuum storage bags (Item 95613)3;
- four 13-dram transparent plastic vials, the caps of which I modified with fine (0.33 sq. mm) mesh;
- screen-covered ventilation ports;
- one Ridgid brand Portable wet/dry Shop-Vac4 (5-hp max.);
- one analog vacuum gauge (item 4FLT5; range: 0 to -30 inches of mercury (inHG); or zero to -100 kilopascals (kPa)5;
- about 3 grams of Loctite brand LocWeld epoxy6; and
- eight sweatshirts.
With epoxy, I sealed the brass stem of the analog vacuum gauge into a hole drilled into the nozzle tool on the hose of the shop vac. I tested its functionality by placing two folded sweatshirts into one of the vacuum storage bags. I operated the shop vac with the nozzle fit tightly to the air-removal port on the vacuum storage bag until it contracted to its apparent minimum volume. I continued for 10 more seconds while observing the vacuum gauge for a stabilized maximum reading (see Fig. 1). I repeated the process twice more to record measurement consistency of the storage bag evacuation process.
I placed bed bug-populated sections of paper towel harborage from my bed bug rearing containers into four vent-cap vials. Each section of harborage contained 50 to 100 live bed bugs, all fed within two to three weeks (except for recently eclosed first-instar nymphs) and representing all developmental stages. I placed one of the bed bug-populated vials between two folded sweatshirts in each of the four vacuum storage bags, which were closed using the airtight press-seal ends.
I used the 5-hp shop vac to evacuate as much air as possible from three of the four vacuum storage bags, the fourth being my control. The shop vac — fitted with a vacuum gauge to measure the extraction of air from the vacuum storage bags — provided a reading on the double-scale analog dial of about -3.4 inHg and -11.5 kPa. I used conversion formulae to translate the level of air pressure reduction achieved in my studies into millimeters of mercury or torrs (-86.36 mmHg equals torrs), and atmospheres (0.87 atm). Despite the contraction of the vacuum storage bags and their contents during evacuation, there remained 0.87 atmosphere of air pressure in the bags.
I observed the evacuated bags periodically to ascertain air wasn’t noticeably seeping back into them. After 24 hours, I opened the bags and removed the vent-cap vials to examine the contained bed bugs. I observed only a few bed bugs, mainly adults, had expired in each vial. No bed bug mortality occurred in the control vent-cap vial.
Would ice be nice?
Plan B was to customize a portion of a 2011 study by Dr. Changlu Wang and two co-researchers at Rutgers University (Wang et al, 2012)7 by substituting the vacuum storage bags for regular heavy-duty plastic bags to determine if items placed and depressurized in them, along with a quantity of dry ice8, could be disinfested from bed bugs. I was driven to devise a reliable, cost-effective method for the public to disinfest personal property of bed bugs.
I repeated all the aforementioned steps except for one additional measure: Before sealing the three test bags, I placed 1 lb. of dry ice, protectively sheathed in a fabric pouch, on the top sweatshirt in each bag. Then I used the shop vac to extract the air, to the extent possible, from the three test bags.
I opened the bags after 48 hours to examine the bed bugs and eggs contained in the four vent-cap vials, including an untreated control bag. Happily, when I examined the 48-hour containerized bed bugs from the three bags with the added dry ice, I found no live bed bugs (see Fig. 2). Furthermore, all bed bug eggs exhibited a yellowish discoloration and slightly reduced width (see Fig. 3). Two adult female bed bugs had expired in the control vial, but the eggs remained viable and later gave rise to nymphs.
In my first study, I demonstrated a -86 torr reduction in air pressure alone won’t kill bed bugs, so another measure must be implemented to enhance asphyxiation of any insects that might be present in containment. The dry ice sublimates to a volume of CO2 that replaces the air evacuated from the storage bags. The one-way air valves built into the air removal ports of the vacuum storage bags allow air and sublimated CO2 inside the bags to be extracted or exit but don’t allow air movement back into the bags.
The CO2 generated from the added quantity of dry ice per storage bag proved adequate to dilute and flush (via the evacuation port valve) most of the remaining air left in the storage bags, post initial evacuation. Finally, the decision to increase the exposure period from 24 to 48 hours prolonged the respiratory stress to the contained bed bugs and eggs and proved adequate to ensure pest asphyxiation.
This two-part study was designed and conducted as a reliable, all-or-nothing evaluation of readily available resources to help pest professionals and urban entomologists better equip the public in the battle against bed bugs.
As a result of my study — and of Wang’s team — I wouldn’t hesitate to recommend a 48-hour exposure of (actual or suspected) bed bug-infested belongings that can tolerate reduced air pressure to dry ice in evacuated vacuum storage bags. I invite those who are blessed with greater investigative resources than I to continue the search for safe, cost-effective ways to disinfest the belongings of those suffering from bed bugs. Presently, a significant reason for bed bug treatment failure is continuing infestation of missed or untreatable personal property. pmp
Dr. Wegner can be contacted at gerry.wegner@varmentguard.com.
REFERENCES
1. Manager, Technical Services, Terminix International, Memphis
2. Mitsubishi Gas Chemical America, New York
3. Harbor Freight Tools, Camarillo, Calif.
4. Emerson Ridgid Power Tools, St. Louis
5. W.W. Grainger Industrial Supply, Lake Forest, Ill.
6. Henkel Consumer Adhesives, Avon, Ohio
7. Wang, Changlu, Lihua Lu and Ming Xu. 2012. “Carbon dioxide fumigation for controlling bed bugs.” J. Med. Entomol. 49(5):1076-1083.
8. Dry ice (frozen carbon dioxide) is available from a variety of sources, including ice cream parlors, gas cylinder supply companies and some big box and grocery stores.
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