The Odor of a Blood-Sucking Nightmare

 It can be a lonely world for a bed bug researcher! Dr. Mark Feldlaufer began his presentation by extending an open invitation to visit his bed bug research lab at the United States Department of Agriculture-Agricultural Research Center in Beltsville, Maryland. He assured us that the offer rarely gets takers, and it is really not surprising, all things considered. As parasites that feed on people and cause itchy welts, bed bugs give people the heebie-jeebies. Just a picture or two of the bed bugs (Fig. 1) was enough to have several attendees visibly cringe, as they imagine the marks and persistent itches that usually follow after bed bug bites. However, Dr. Feldlaufer’s fascinating research, which aims to improve bed bug detection and control, may contribute to a future where everyone can rest assured that there truly are no creatures lurking under the bed.

Figure 1: Close up of bed bugs in varying life stages. The smallest insects are young nymphs, while the largest insects are wingless adults. Adult bed bugs are approximately 0.18 inches or 4.5mm long (Photo courtesy of: USDA)

Bed bugs (Cimex lectularius), a group of true bugs (Hemiptera) in the family Cimicidae, are infamous for specializing on the blood of birds and mammals including humans. Like little vampires, they pierce the skin and suck blood from their prey. Bed bugs have plagued humanity for centuries. The many colorful nicknames for bed bugs (“crimson ramblers,” “mahogany flats,” “wall lice,” “chinches,” “brown backs,” “red coats,” etc.) highlight the fear, attention, and often even phobia, that they cause. Unsurprisingly, Dr. Feldlaufer most commonly fields the questions: “Do I have bed bugs?” and “How can I get rid of them?” To better answer these questions, he uses chemical ecology to develop tools for bed bug detection and control.

Figure 2: A woman training Brea, a German shepherd search and rescue dog, to use her refined sense of smell to locate missing persons by detecting their odor. Photo Credit: Sgt. John Crosby (Wikipedia Creative Commons)

Detecting bed bugs can be difficult. They are cryptic insects that hide most of the time and emerge at night to feed on blood. They often hide together in cracks and crevices, a behavior called “aggregation.” They prefer to be sandwiched between objects. Thus, they are rather difficult to see, but, thankfully, not more difficult to smell. We are accustomed to seeing trained dogs sniffing around to find drugs, explosives, or missing people (Fig. 2). However, what many may not know is that trained dogs are also one of the most effective methods to detect bed bugs (Pfiester et al. 2008). In a controlled experiment in hotel rooms, trained dogs were 98% accurate in locating live bed bugs. However, this method can vary significantly in effectiveness depending on the dog’s mood, how tired it is, and potential distractions. But the most significant biases often stem from human error, such as the attitude of the trainer. The dog is often able to sense if a trainer strongly believes that there may or may not be bed bugs in a particular location and is far more prone to falsely detect or fail to detect the target (Lit et al. 2011).

Figure 3: Bed bug colonies in mason jars. Bed bug frass is visible on the paper towels, and shed skins pile at the base of the jars. (Photo courtesy of: Dr. Mark Feldlaufer)

In a setting where there are high numbers of bed bugs, their presence can be apparent even without trained dogs. While developing, bed bugs shed their skin, which look like cream-colored crumbs, and their frass (fecal matter) which look like sooty black stains (Fig. 3). It is also possible, although unusual, to see a bed bug fleeing the scene. Nonetheless, in those critical times when an infestation is just beginning to establish, populations are small and difficult to locate. This is when the merits of bed bug detecting dogs become clear. Properly trained dogs (and handlers) can be used to detect infestations early when populations are smaller and easier to control.

often do not come in contact with them. It is impractical, dangerous, and against labelled usage, to coat every surface and crack of a home or business in insecticide, so bed bug chemical treatments often fail. The silver bullet control method appears to be heat treatments, but, like silver, heat treatments are expensive. Homes are heated to between 120-140⁰F for several hours to kill all bed bug life stages, which tend to cost anywhere between $2,500-$7,000. Though bed bugs themselves do not discriminate against the rich or poor, our methods of remediation tend to do just that. The most effective way to get rid of bed bugs is unaffordable to many.

In the course of his bed bug research, Dr. Feldlaufer has worked on other projects to help to detect and control bed bugs early in their infestations with a number of students, including our very own Dr. Kevin Ulrich. The team found that bed bugs consistently avoided a common chemical insect repellent, DEET, the main ingredient in most mosquito repellents. They did not, however, respond with greater avoidance to higher dosage. Although this may seem like a quick and easy fix, wearing DEET to bed may just cause bed bugs to merely move on to other surfaces (e.g. the couch). On the other hand, they also found that aldehyde compounds produced by bed bugs elicit a strong attractive response to other adult and immature bed bugs. These aldehydes may be one way bed bugs attract each other to form aggregations (Ulrich et al. 2016), suggesting that the aldehydes may be used to develop an inexpensive and more discreet option to lure and trap bed bugs. Dr. Feldlaufer currently aims to develop and test reduced risk pesticides that show promise in killing bed bugs.

Bed bugs can be a terribly menacing presence in anyone’s home, but thankfully Dr. Feldlaufer has dedicated much of his career to keeping us informed about these insects and their crafty activities. By pairing lures with reduced risk pesticides, Dr. Feldlaufer aims to develop options to safely, affordably, and discreetly ensure we can sleep tight assured that the bed bugs will not bite.

References:

Lit L., Schweitzer J.B., and Oberbauer A.M. 2011. Handler beliefs affect scent detection dog outcomes. Animal Cognition 14: 387.
Pfiester M., Koehler P.G., and Pereira R.M. 2008. Ability of bed bug-detecting canines to locate live bed bugs and viable bed bug eggs. Journal of Economic Entomology 101(4):1389-96.

Ulrich, K.R., Kramer, M. and Feldlaufer, M.F. 2016. Ability of bed bug (Hemiptera: Cimicidae) defensive secretions (E)-2-hexenal and (E)-2-octenal to attract adults of the common bed bug Cimex lectularius. Physiological Entomology 41: 103-110.

Author Bio:

Hanna Kahl is a master’s student at University of Maryland in Dr. Cerruti Hooks’ lab researching the effects of red clover living mulch on arthropod pests and pollinators.

Samuel Ramsey is a PhD student at University of Maryland in Dr. Dennis vanEngelsdorp’s lab researching Varroa destructor.