NMR was the key to finding hidden components of bed bug pheromone mixture
Common bed bugs, Cimex lectularius (Hemiptera: Cimicidae), have become a global epidemic. Bed bug injuries treated in the United States went from 21 in 2000 to more than 15,000 in 2010. The most likely causes of the resurgence include international travel, sales of used furnishings, insecticide resistance and changes in pest control.
A growing problem, bed bugs are not a scourge of just dirty and low-rent locales. The parasites live on blood found in the toniest and lowliest of places. In fact, they set up shop at upscale clothiers, grace the linens of elegant hotels and stow away in designer luggage for global journeys. Perhaps most disturbing, the six-legged, hard-shelled pests embed themselves in your very bed making themselves at home in your home sweet home.
Despite universal repulsion, they thrive. They have been the subject of a New York Times editorial, “In Search of a Bed Bug Solution” and have a dedicated Bed Bug Registry – quite a testament to the widespread, growing concern and the difficulty of eliminating the parasite. Bed bug bites can cause skin irritation and allergic reactions, and their presence elicits unanimous disgust.
Avoid, detect, treat and monitor
People go to great lengths to avoid bed bugs. Travelers purchase special sleeping envelopes and luggage shells. At home, people encase mattresses in fabric designed to block bugs. But, avoidance doesn’t always work.
If and when the bugs invade, it isn’t easy or quick to detect the problem. Bed bugs are tiny and flat. They burrow into narrow crevices in furniture, grip onto the seams of bedding and hide inside electrical outlets. Even careful examination can miss the signs. Some experts have taken to employing bed-bug sniffing dogs, with varying degrees of accuracy, hardly a scalable solution. To date, there are no practical, accurate and affordable methods of detecting bed bugs.
To make matters worse, once detected, bed bugs are difficult to eradicate. They are resistant to many chemicals. The few pesticides that are capable of killing them are notoriously dangerous. Home-spun remedies, including covering bed legs with Vaseline so the bugs cannot climb up to the mattress and creating a trap using Alka-Seltzer, are well-meaning but of limited, if any, actual efficacy. Covering mattresses and thorough vacuuming can reduce bed bug presence, but they rarely eliminate it.
What do you do with a problem like bed bugs? Beat them at their own game
Until recently, there was incomplete information on what makes bed bugs tick. Researchers sought to better understand bed bug behavior. What draws them to a spot? Why do they stick together? Why do they settle in and stay in a certain area? Perhaps most important, how can we use their own behavior against them?
Although researchers have been investigating the natural chemicals that signal the bugs to gather, or aggregate, identifying the exact composition of the pheromone mix has been difficult.
Researchers at Canada’s Simon Fraser University have been working for years to better understand bed bugs. They knew some of the pheromone components that were critical to bed bug behavior, and used those as the basis of a lure that might replicate the pheromone mixture found in nature. Despite their best efforts, the scientists were stymied: No lab mixture effectively lured the bugs in real-world situations. Something was missing. The researchers kept at it in the hope of finding effective ways to detect and potentially lure the parasites into a trap.
A tool for the job
Suspecting that a crucial component might not be detected by the tools they were using, researchers started analyzing bed bug husks and excrement using two Bruker Avance 600 MHz NMR spectrometers. The suspicions proved true. NMR revealed the natural mixture included histamine, which, because of its structure, could not have been detected using more traditional methods.
Identifying histamine was a big step forward. Still, bed bugs did not always respond to the new mixture, even with the addition of histamine. Again, the researchers hypothesized that other difficult-to-identify components might be in the natural mix. Finally, the team found a solution, a special blend of volatile compounds and histamine that together effectively tempted and trapped bed bugs. The stumbling block all along was the limitation of the technology. By using the advanced capabilities of NMR, the researchers revealed the composition of the molecular scent that effectively elicits gathering and arresting behavior.
Their research, “Bed Bug Aggregation Pheromone Finally Identified,” was published in the journal Angewandte Chemie. The bed bug aggregation pheromone consists of five volatile components — dimethyl disulfide, dimethyl trisulfide, (E)-2-hexenal, and (E)-2-octenal, 2-hexanone. These chemicals tempt bed bugs to safe places. A sixth less-volatile and more difficult to identify component, histamine, causes bed bug arrestment on contact.
Now, the researchers are working to develop a trap that is easy to make, affordable to buy and simple to use. They are taking what NMR revealed about bed bug pheromones and creating a test people can use in the real world to identify infestations, trap bed bugs and monitor treatment. The elusive six-part pheromone cocktail is becoming a last call for the six-legged pest.