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Bed Bugs: A Chink In The Armor?

Posted Mar 28 2013 10:01pm

Posted on | March 27, 2013 |

Back in  2010, Cimex lectularius was all the rage. Bed bugs -  nearly impossible to get rid of (having developed resistant to most insecticides); striking in the middle of the night and sucking your blood (you don’t feel the bite because the bug injects an anaesthetic and anticoagulent into your skin); and for leaving you with itchy trail marks, a bad reputation, and insomnia.

Turns out bed bugs weren’t anything new.  They used to be very common, estimated to have been in 30% of all American homes just before World War II. Then they all but disappeared with the widespread use of residential pesticides post-World War II until around 1998 when they started to be reported again in the US and other countries around the world. Why?

Well bed bugs are on the move, and a new report on the genomics of bed bugs this month is finally providing some answers.(1)

More on that in a moment. First, a few facts courtesy of Cornell .

Bed bugs are insects of the Order Hemiptera and Family Cimicidae, which has over 90 species around the world and 15 in North America. Bed bugs and their relatives are wingless, blood-feeding parasites of animals. The common bed bug (Cimex lectularius) is a pest of humans this species has recently become a problem in the United States and countries all over the world.

Bed bugs have three basic life stages; egg, nymph, and adult. They begin as a very small but visible egg, hatch to become a first instar nymph or juvenile, which is 1 millimeter long or about the size of a poppy seed. There are five juvenile stages, which feed on blood, molt and grow over time. The adult is about the size of an apple seed.

Bed bugs tend to gather together in hidden and undisturbed places where a person sleeps, or sits for an extended period of time. They are usually found in the bed, along the seams and sides of the mattress and box spring, the headboard, and bed frame, creating clusters of live bed bugs, shed skins, dark-colored fecal spots, and eggs. In heavily infested locations bed bugs can be found anywhere in the room. As bed bugs grow they shed their amber-colored, transparent skins, leaving behind what look like hollow bed bugs.

A fecal spot, the result of bed bug digestion, may look like a brownish-black bump on a hard surface, or a dark stain (like a magic marker dot) on fabric. Eggs are cemented to fabric, wood, paper, and most other surfaces as the female hides or wanders in search of a host.


It is unclear exactly why and from where bed bugs re-emerged as a pest in our homes, dormitories, hotels, and shelters, but the resurgence was noticed throughout the world in the late 1990’s.  Recent studies suggest that bedbugs spread has been facilitated in our mobile global society. In short, they hitch a ride most often with our furniture when we move to new locations.

Bed bugs must bite to feed on blood. They have pointed mouth parts, like mosquitoes, and feed for just a few minutes at a time. They must feed to grow and although they primarily feed at night, bed bugs will bite during the day if necessary.  Bed bugs have never been shown to transmit disease to humans. The most common symptom of bed bug bites are itchy welts on the skin.

Bed bugs are small but visible insects. There are three main life stages: the whitish egg (about 1 mm in length), five pale juvenile (nymph) stages that range from 1mm to 4.5 mm (1/4 inch), and the adult which can be as long as 7 or 8 mm (3/8 inch) when fed. The newly hatched nymph is very pale until it feeds. Then it looks like a tiny droplet of blood. Each nymph stage will feed and become filled with red blood. The adult is about the size and shape of an apple seed, and dark red to brown in color and as flat as a credit card before feeding.

The simple answer is “not as easily as you used to” according to a recent study published in National Geographic’s online Scientific Reports.(1,2) It seems the bed bug has developed resistance to pyrethroid insecticides which are commonly used in professional bed bug control because of their relative safety for humans and pets. The scientists studied the genes of 20 pyrethroid-resistant populations of insects from around the nation, comparing them to a none resistant population. The results?

Fourteen molecular markers of resistance were detected. But most point to a growing ability by the bugs to use their hard outer cuticle shell to prevent the insecticide from ever entering their bodies and reaching their nervous systems where the insecticide works.

Researchers say that now that they can identify the sites of resistance, they will be better able to fight the bugs. Rutgers expert Changlu Wang says, “that better formulations can be designed to penetrate the cuticle more effectively and thus provide better control.” A second strategy that involves a rotation of different a gets in a prescriptive scheme is also being tested.

What the study also proved is that bugs on opposite ends of the country were intimately related. How’s that possible? They hitched a ride on moving vans hidden away in furniture. So while the researchers continue their progress, we can lend a hand by carefully examining sofas, beds, and other furniture before we place it on the road.

For Health Commentary, I’m Mike Magee

Refeences:
1. Zhu F et al.Bed bugs evolved unique adaptive strategy to resist pyerethroid insecticides. Scientific Reports 3:1456. March 14, 2013. http://www.nature.com/srep/2013/130314/srep01456/full/srep01456.html
2. Than K, US Bedbugs evolve multiple ways of thwarting insecticides. National Geographic. March 14,2013.

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