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Bed Bugs
By: Dr. Richard Kaae |
The common bed bug (Cimex lectularius) is the main species that is currently found infesting buildings and homes throughout the United States and other temperate climates. The name bedbug is somewhat of a misnomer. These insects are not necessarily found in or around beds but since the common bedbug pest in the US feeds on human blood during evening hours it follows that they most commonly occur around or on beds as this is where the food is, namely us.
Bed Bug with Piercing Sucking Mouthparts Inserted into host (human_ sucking blood. Image Courtesy CDC.
It is thought that Cimex lectularius was originally an ectoparasite of bats in caves, but then changed hosts to include humans (cavemen) once they were found in the same habitat. Bedbugs were originally brought to the United States by early colonists from Europe. At one point with the advent and use of modern pesticides and improved sanitation, infestations in many areas greatly decreased. They were believed to be almost eradicated 50 years ago in the United States and elsewhere with the widespread use of DDT. In many undeveloped countries however the bedbug remained an important pest. In the past several years we have encountered many more bedbug infestations in the United States and many other countries. It is this thought that this significant increase is possibly due to a number of factors including an increase in worldwide travel and corresponding accidental importation of bedbugs in suitcases, cargo and similar materials. Another recent theory about their reappearance involves potential geographic epicenters. Investigators have found three apparent United States epicenters at poultry facilities in Arkansas, Texas, and Delaware. It was determined that workers in these facilities were the main spreaders of bedbugs, unknowingly transporting them from the poultry farms to their places of residence and elsewhere. Bedbug populations in the United States have increased by 500 percent in the past few years.
In addition the use of baits rather than insecticide sprays for cockroach control could have also added to their increased presence. These residual sprays that were used in hotels and other locations for control of the German cockroach could have simultaneously been controlling bedbugs. Many professional consider it no coincidence that the dramatic rise in bedbug activity came approximately 10 or so years after applicators stopped spraying for cockroach activity.
Infestations. A few of the major cities that are currently experiencing considerable bedbug’s infestations include Los Angeles, San Francisco and New York. New York City has experienced increased cases of bedbug infestations since the early 2000s, with some reported in hotels, schools, and hospitals. In 2004, New York City had 377 bedbug violations. However, in the five-month span from July to November 2005, 449 violations were reported in the city, a considerable increase in infestations over a short period of time. Some domestic cases have escalated to extreme levels, causing residents to label the infestations "house herpes". Exterminators and entomologists blame the infestations on the fact that so many international travelers visit New York City each day.
The number of bedbug infestations has risen significantly since the early 21st century. The National Pest Management Association reported a 71% increase in bedbug calls between 2000 and 2005. The Steritech Group, a pest-management company based in Charlotte, North Carolina, claimed that 25% of the 700 hotels they surveyed between 2002 and 2006 needed bedbug treatment. In 2003, Burl and Desiree Mathias, a brother and sister staying at a Motel 6 in Chicago were awarded $372,000 in punitive damages and $10,000 in actual damages after being bitten by bedbugs during their stay. These are only a few of the reported cases since the turn of the 21st century.
Biology. The adults of this species are wingless, flattened, reddish brown, and about 1/4 inch long. Newly hatched nymphs are translucent, lighter in color, quite small (about the size of a dot on this page.) As they molt (5 nymphal instars) and periodically increase in size until reaching the adult stage, they progressively become darker in coloration. Nymphal instars require one blood feeding between each molt. A common misconception is that they are not visible; however, even the early instar nymphs are visible to the naked eye. The female also requires a blood meal before laying eggs at the rate of 2 to 3 each day. On an average during her lifetime the female deposits 200 or more eggs in cracks, crevices, under loose wallpaper or similar locations. The eggs hatch in one to two weeks and nymphal development may require from 10 weeks to 6 months, depending on prevailing temperatures and availability of food. Since insects are cold blooded their body temperate remains close to that of their surrounding environment; consequently, the colder the prevailing temperature the longer the developmental period. Nymphs and adults are gregarious (found together in groups) and hide during the day - normally venturing out to feed in the early morning hours but occasionally feed at other times if given the opportunity and have been observed active during all periods of the day. Typically only when bedbugs are starved will they feed during daylight hours. Common daytime hiding places include the seams (top and bottom) of mattresses-especially near the “head end” of the bed which is typically warmer. Bedbugs are also commonly found behind the headboard, especially if it is touching the wall. Any objects (pictures on the wall, nightstands next to a bed, etc.) that is close to a bed are common hiding location although with a heavy infestation bedbugs can be found throughout the structure. They can gain access to their host by crawling up the legs of a bed or they have even been observed crawling across and dropping from the ceiling to float (flattened like a falling leaf) down to their host. These are remarkably hardy insects.
Common Bedbug, Cimex lectularis. Image courtesy CDC.
Aggregation of Bedbugs. Image Courtesy w.en. User Rogesoss
The bug pierces the skin of a host with two hollow feeding tubes. One functions to inject saliva, which contains anticoagulants and anesthetics, while the other withdraws the blood of the host. The anticoagulant serves to keep blood flowing (preventing coagulation) in the tiny mouthparts while the anesthetic servers to numb the area and prevent detection of their presence. After feeding for about five minutes the bug returns to its hiding location. The bite cannot usually be felt until minutes or hours later with the first indication of a bite usually occurring from the desire to scratch the area. Without a source of food bedbugs can enter a dormant condition and can live for 18 months while well-fed specimens typically live six to nine months.
Bedbug Piercing Sucking Mouthparts. Image Courtesy CDC.
Although bedbugs can live for a year or eighteen months without feeding, and reportedly up to three years in the case of the species Oeciacus vicarius (the cliff swallow bug), they normally try to feed every five to ten days.
The mating behavior of bedbugs is strange and at times quite competitive. Males inject their sperm into the female by puncturing the body wall as the female has no natural opening for reception of his sperm. Of course the sperm then swim throughout the female’s body cavity eventually finding and fertilizing her eggs. Apparently this is not limited to females as it is not uncommon to find males with copulation scars where other males have penetrated their body wall. In some species this apparently happens when a male penetrates another male that is copulating with a female and injects his sperm into the mounted male. In this case some of his sperm find its way into the sperm ducts of the mounted male which in turn is injected into the female upon ejaculation.
Bedbugs in Traumatic Insemination. Image Courtesy of Rickard Ignell, Swedish University of Agricultural Sciences
Symptoms of Bites and Treatment. A typical human reaction due to bed bug feeding consists of a raised red or flat welt which is often accompanied by very intense itching. The red mark is the result of the body’s reaction to the anesthetic in the bedbug’s saliva. This symptom of bedbug bites is quite similar to that of a mosquito but in the case of the former the welt tends to last longer than that of the latter. Also mosquito bite (at least those occurring while sleeping) are typically found on the face or other areas not covered while those of bedbugs can occur all over the body. Bedbug bites may not become immediately visible and can take up to nine days to appear. Bedbug bites tend not to have a red dot in the center such as is characteristic of flea bites. A trait shared with flea bites is tendency towards the pattern of sequential bites often aligned in rows of three. This may be caused by the bedbug being disturbed while eating and relocating half an inch or so farther along the skin before resuming feeding. Alternatively, the arrangement of bites may be caused by the bedbug repeatedly searching for a blood vein.
People react differently to bedbug bites possibly due to differences skin type, environment, and the species of bug. It is possible for an initial infestation within a household to be asymptomatic and go undetected. In some rare cases, allergic reactions to the bites may cause nausea and illness. In a large number of cases, estimated to be fifty percent of all people, there is no visible sign of bites whatsoever, greatly increasing the difficulty of identifying and eradicating infestations. The mere thought of these vermin sucking one’s blood can be very stressful and can result in delusory parasitosis with victims developing an overwhelming obsession with bedbugs. In some cases this occurs even to the extent with lack of the present of these insects. Secondary skin infections are common due to obsessive scratch in the welts.
Systemic corticosteroids for treating the itching and burning often associated with bedbug bites in many cases are less than effective. Antihistamines can reduce itching in some cases, but typically do not affect the appearance and duration of the lesions. Topical corticosteroids, such as hydrocortisone, reportedly are effective in reducing lesions and decreasing the associated itching.
Application of heat (blow-dryer, hot washcloth, hot water)) can be effective in relieving itching and inflammation for several hours. The water temperature should be about 50 °C (120 °F), or this procedure may aggravate the symptoms. To avoid scalding the skin, this treatment should only be self-administered.
Means of Home Infestations. There are several ways in which dwellings can become infested with bedbugs. One common way is to picked them up while traveling or when staying in hotels, bed-and-breakfasts, hostels, or motels-which are places that have been traditionally associated with an increased risk for bedbugs due to their higher rate of turnover and continual influx of temporary residents. Once acquired at such travel locations, the now hitchhiking bedbugs may then be transported and brought back to the homes of the guests in their luggage.
Bedbugs can also be acquired through bringing infested furniture or contaminated, used clothing into a household. Furniture does not necessarily have to have been previously owned or discarded-as even brand new furniture can be exposed to bedbugs during storage or in delivery vehicles. Toys such as stuffed dolls or other bedroom items can be infested as well.
Bedbugs infest a new residence by traveling between multi-unit housing such as condominiums, dormitories, and apartment buildings, or arrive after having exited infested furniture that has been thrown out, discarded and/or placed outside for garbage collection or for treatment. This unintentional spread between adjacent home sites and nearby units is dependent, in part, upon the degree of infestation at the source (i.e. a heavier infestation is more likely to spread), but also upon the building material used to partition units and the material used to seal connecting pipes, vents, wires, etc. Further potential to spread is also directly related to the manner in which infested items are disposed of-such as whether or not contaminated furniture is dragged through common areas while being removed.
In locations that are severely infested, bedbugs may actually crawl onto a person’s clothes and be carried from location to location. It is also common for bedbugs to nest in clothing articles that are generally not frequently washed and for them to then spread when such apparel is either stored publicly with other apparel (as in locker rooms and on coat racks). Otherwise, bedbugs will not be usually carried from place to place by people on the clothing they are currently wearing. General machine washing and drying on high heat will kill all stages of bedbugs.
The size of a bedbug infestation can range from a few to thousands, or even tens of thousands. A single bedbug brought into a home has a potential for reproduction with its resulting offspring then breeding and potentially leading to a geometric progression of their numbers. In any case, bedbugs reproduce prolifically and it is not at all unusual for exterminators to encounter thousands of bedbugs in even a single mattress. Sometimes people are not aware of the insects and do not notice the bites. The visible bedbug infestation does not represent the infestation as a whole, as there may be infestations elsewhere in a home and the sighting of one bedbug typically means that there may be many more in hiding. However, the insects do have a tendency to stay close to their hosts, hence the name ’bed’ bugs.
Bedbugs and Disease. Bedbugs appear to possess all of the necessary criteria for transmitting diseases, but there have been no known cases of these pests vectoring or transmitting any disease. There are a few dozen or more know pathogens that are capable of living inside a bed bug or on its mouthparts. However, numerous laboratory studies indicate that bedbugs are unlikely transmit these pathogens to humans. Therefore from a disease transmission standpoint bedbugs are considered less dangerous than some more common insects such as the flea.
Detection of Infestations. As indicated detection of bedbug infestations can be aided by the use of bed bug detection dogs that have been trained to find bedbugs by their scent. A trained bedbug dog and handler can detect and pinpoint a bedbug infestation within minutes. Apparently these trained dogs can detect or smell as little as 1/1000 of a bedbug. This remains a fairly costly service that is not used in the majority of cases.
An Engorged Female Bedbug in the Screw Hole of a Wooden Bed Frame. Image courtesy CDC.
Bedbugs travel easily and quickly along pipes and boards, and their bodies are very flat, which allows them to hide in tiny crevices. They tend not to travel further than 100 feet (30 m) from their host to feed. Typical symptoms of a bedbug infestation may include fecal spots, crushed bedbugs and/or bloodstains on the sheets, cast skins and the development of itchy welts from their bites (in those that react). Use of a crevice tool to reach into small spaces as well as the use of a magnifying glass and/or flashlight can assist in the successful detection of bedbugs and their symptoms. A crevice tool, however, can be improvised but - very importantly - should consist of a non-conductive material such as plastic or wood if it is to be used to probe walls, baseboards, and/or electronics, etc. (to prevent electric shock).
The presence of defecations will be one of the primary signs of an infestation. As bedbug droppings are black or nearly black in color, they will often appear as dots or specks that are similar in appearance to a dried drop of ink. The feces is digested blood. These small pitch-black droppings will vary in size (ranging from tiny and difficult to see up to the size of the bugs themselves) but can be distinguished from other dark debris in that it will readily smear (or bleed in color) if exposed to water. Rubbing the black fecal spots with a wet wipe will work well. The deposits may also be found, not as circular dots, but as dark pinstripe-like markings that are small and streaked in appearance. Feces will occur anywhere bedbugs may be harbored but might also be found at the location of the host site or along route back to a nesting location - i.e. which might be on the pillowcase or, mattress, sheets, bed frame, curtains, in baseboards, in crevices, in seams, under the couch, under chairs, etc. Successful detection of a bedbug’s defecations might require a considerable degree of extra vigilance and careful searching in light cases of infestation.
The presence of cast skins is another indication that they are present but, perhaps, well hidden. Bedbugs will shed their skins throughout multiple stages of their lives and the discarded outer-shells (which will vary in size according to the stage and can be extremely small) might be found near any of the various locations where they have harbored. The sloughed off skins (pictured above) will appear as clear, empty exoskeletons of the bugs themselves. And the actual living bugs may or may not be nearby the discarded shells.
The presence of bedbugs may also be confirmed through direct discovery and identification of the insects collected or by a pattern of bites. Though bites can occur singularly, they often follow a distinctive linear pattern marking the paths of blood vessels running close to the surface of the skin. It should also be noted that confirmed bedbugs may vary slightly (or even markedly) in appearance, color, or shape and depending on the insect’s current size, stage in life, and whether or not they have recently fed.
A technique for catching bedbugs in the act is to have a light source quickly accessible from your bed and to turn it on at about an hour before dawn, which is usually the time when bedbugs are most active. A flashlight is recommended instead of room lights, as the act of getting out of bed will cause any bedbugs present to scatter before you can catch them. Bedbugs are fairly fast in their movements, about equal to the speed of ants. They may be slowed down if they have engorged on their food source. When the bedroom light is switched on, it may temporarily startle them allowing time for you to get a dust pan and brush kept next to the bed and sweep the bugs into the pan then immediately sweep them into a cup or mug full of water where the bugs drown quickly.
Control. High temperatures are used as a means of controlling bed bugs. A laundry dryer (120 F) or higher will effectively kill any infesting bedbug stages. Small steam cleaners have been very effective for local treatment. Ant stage of the common bedbug (C. lectularius) is killed by exposure of temperatures of 115 F for 7 minutes. However, to ensure that bedbugs do not survive by hiding in locations that do not quite reach that point, the US Department of Defense recommends using a temperature of at least (120 °F), at 20-30% relative humidity for at least 20 minutes. Oven-like devices are commercially available for such purposes. Enclosing a mattress in a black plastic bag and placing it in the sun on a hot day is not considered an effective method of killing bedbugs. This is mainly due to the fact due to the possibility of not maintaining a high temperature across the entire surface area of the mattress. The use of cold in controlling bedbugs is much less effective. Most insects including bedbugs can survive colder temperatures as opposed to hot temperatures. There is uncertainty as to how long bedbugs can survive cold temperatures. For example below 16.1 °C (61 °F), adult bedbugs enter semi-hibernation and can survive for an extended period of time. As a result it is generally considered much more economical and effective to use heat as opposed to extreme cold to control these pests. It is believed that storing infested items below - 19 °C (0 °F) for at least four days will kill these pests.
In some cases it is very difficult or costly to eliminate bedbugs from a structure. As a result a bed can be isolated, thus removing the insects’ food source (namely humans) provided the bed is clean from existing bedbugs. Bedbugs cannot cross petroleum jelly and have difficulty climbing metal and glass, hence each of the bed legs can be placed in a tin can (the bottom of which is thickly coated with petroleum jelly) to avoid movement to the bed. However as previously mentioned they have been observed climbing a higher surface in order to then fall to a lower one thus avoid the protected legs. Of course when it is necessary to live with bedbugs in the short term (either during treatment or while in the process of figuring out the best approach for treatment), it is possible to create a makeshift, temporary barrier around a bed that will help prevent bedbugs from crawling to a bed.
A disinfected bed can be isolated and protected by applying one or more layer of duct tape around each leg of the bed-using regular duct tape that has been curled lengthwise over on itself with the sticky side out. Typically, isolating a bed should be done only after encasing both the mattress and the box spring in combination with successfully disinfecting the entire bed frame. Mattresses can be encased using zippered vinyl or plastic mattress encasements. A mattress can also be fully covered and sealed using mattress encasements that are specially designed either for bedbugs. These are readily available.
Duct Tape Barrier on Bed Leg
Vermin (rat and mice) and pets may also complicate a barrier strategy. Bedbugs prefer human hosts, but will resort to other warm-blooded hosts if humans are not available, and some species can live up to eighteen months without feeding at all. An infestation of mice can provide an auxiliary food source to keep bedbugs established for longer or the isolating of a bedbug’s food source may cause the infestation to spread. Likewise, a house cat or human guest might easily defeat a barrier by sitting on a protected bed. Preventing the bed from touching the walls, as well as preventing bedding from draping the floor, or not allowing objects to lean against the bed frame will help to stop bedbugs from being reintroduced onto the bed. Such considerations should be part of any barrier strategy.
Dr. Richard Kaae, has over forty years of experience in the field of Entomology. Dr. Kaae is currently a Professor of Pest Management & Entomology at Cal Poly Pomona and has owned his own Pest Control Company for twenty years. Dr. Kaae's website Pesteducation.com offers online continuing education for pest control license renewal and is accredited by all states and internationally.
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