Bed bug

Bed bugs are insects from the genus ''Cimex'' that feed on blood, usually at night. Their bites can result in a number of health impacts including skin rashes, psychological effects, and allergic symptoms. Bed bug bites may lead to skin changes ranging from small areas of redness to prominent blisters. Symptoms may take between minutes to days to appear and itchiness is generally present. Some individuals may feel tired or have a fever. Typically, uncovered areas of the body are affected. Their bites are not known to transmit any infectious disease. Complications may rarely include areas of dead skin or vasculitis.

Bed bug bites are caused primarily by two species of insects: ''Cimex lectularius'' (the common bed bug) and ''Cimex hemipterus'', found primarily in the tropics. Their size ranges between 1 and 7 mm. They spread by crawling between nearby locations or by being carried within personal items. Infestation is rarely due to a lack of hygiene but is more common in high-density areas. Diagnosis involves both finding the bugs and the occurrence of compatible symptoms. Bed bugs spend much of their time in dark, hidden locations like mattress seams, or cracks in a wall.

Treatment is directed towards the symptoms. Eliminating bed bugs from the home is often difficult, partly because bed bugs can survive up to 70 days without feeding. Repeated treatments of a home may be required. These treatments may include heating the room to for more than 90 minutes, frequent vacuuming, washing clothing at high temperatures, and the use of various pesticides.

Bed bugs occur in all regions of the globe. Infestations are relatively common, following an increase since the 1990s. The exact causes of this increase are unclear; theories including increased human travel, more frequent exchange of second-hand furnishings, a greater focus on control of other pests, and increasing resistance to pesticides. Bed bugs have been known human parasites for thousands of years.

Signs and symptoms

Skin

The most common skin findings associated with bed bugs are pruritic, maculopapular, erythematous lesions. Each lesion is about 2–5 mm but may be as large as 2 cm in diameter and there may or may not be the presence of a central punctum. Bites are usually present on areas of exposed skin, especially exposed areas not covered by sheets or blankets, such as arms, legs, feet, face or neck. Individual responses to bites vary, ranging from no visible effect (in about 20–70%), to small flat (macular) spots, to the formation of prominent blisters (wheals and bullae) along with intense itching that may last several days. Vesicles and nodules may also form. The lesions due to bites may become secondarily infected due to scratching but systemic effects from bed bug bites are very rare. A central spot of bleeding may also occur due to the release of blood thinning substances in the bug's saliva.

Symptoms may not appear until some days after the bites have occurred. Reactions often become brisker after multiple bites due to possible sensitization to the salivary proteins of the bed bug. Numerous bites may lead to a red rash or hives.

Psychological

Serious infestations and chronic attacks can cause anxiety, stress, and sleep difficulties. Development of refractory delusional parasitosis is possible, as a person develops an overwhelming obsession with bed bugs.

Other

A number of other symptoms may occur from either the bite of the bed bugs or from their exposure. Serious allergic reactions including anaphylaxis from the injection of serum and other nonspecific proteins have been rarely documented. Due to each bite taking a tiny amount of blood, the chronic or severe infestation may lead to anemia. Bacterial skin infection may occur due to skin breakdown from scratching.
Systemic poisoning may occur if the bites are numerous. Exposure to bed bugs may trigger an asthma attack via the effects of airborne allergens although evidence of this association is limited. There is no evidence that bed bugs transmit infectious diseases even though they appear physically capable of carrying pathogens and this possibility has been investigated. The bite itself may be painful thus resulting in poor sleep and worse work performance.

Bed bugs can feed on warm-blooded animals other than humans, such as pets. The signs left by the bites are the same as in the case of people and cause identical symptoms (skin irritation, scratching etc.). Bed bugs can infest poultry sheds and cause anemia and a decrease in egg production in hens.

Insect

Bed bug infestations are primarily the result of two species of insects from genus ''Cimex'': ''Cimex lectularius'' (the common bed bug) and ''Cimex hemipterus'' (the tropical bed bug). These insects feed exclusively on blood and, at any stage of development, may survive up to 70 days without feeding. Adult ''Cimex'' are light brown to reddish-brown, flat, oval, and have no hind wings. The front wings are vestigial and reduced to pad-like structures. Adults grow to long and wide. Female common bed bugs can lay 1–10 eggs per day and 200–500 eggs in their lifetime, whereas female tropical bed bugs can lay about 50 eggs in their lifetime .

Bed bugs have five immature nymph life stages and a final sexually mature adult stage. Bed bugs need at least one blood meal in order to advance to the next stage of development. They shed their skins through ecdysis at each stage, discarding their outer exoskeleton. Newly hatched nymphs are translucent, lighter in color, and become browner as they moult and reach maturity. Bed bugs may be mistaken for other insects, such as booklice, small cockroaches, or carpet beetles; however, when warm and active, their movements are more ant-like, and like most other true bugs, they emit a characteristic disagreeable odor when crushed.

Bed bugs are obligatory bloodsuckers. They have mouth parts that saw through the skin and inject saliva with anticoagulants and painkillers. Sensitivity of humans varies from extreme allergic reaction to no reaction at all (about 20%). The bite usually produces a swelling with no red spot, but when many bugs feed on a small area, reddish spots may appear after the swelling subsides. Bedbugs prefer exposed skin, preferably the face, neck, and arms of a sleeping person.

Bed bugs are attracted to their hosts primarily by carbon dioxide, secondarily by warmth, and also by certain chemicals. There is strong evidence that bed bugs can respond and orient towards human odors, independently of all other host cues. ''Cimex lectularius'' feeds only every five to seven days, which suggests that it does not spend the majority of its life searching for a host. When a bed bug is starved, it leaves its shelter and searches for a host. It returns to its shelter after successful feeding or if it encounters exposure to light. ''Cimex lectularius'' aggregate under all life stages and mating conditions. Bed bugs may choose to aggregate because of predation, resistance to desiccation, and more opportunities to find a mate. Airborne pheromones are responsible for aggregations.

Spread

Infestation is rarely caused by a lack of hygiene. Transfer to new places is usually in the personal items of the human they feed upon. Dwellings can become infested with bed bugs in a variety of ways, such as:
* Bugs and eggs inadvertently brought in from other infested dwellings on a visiting person's clothing or luggage;
* Infested items (such as furniture especially beds or couches, clothing, or backpacks) brought into a home or business;
* Proximity of infested dwellings or items, if easy routes are available for travel, e.g. through ducts or false ceilings;
* Wild animals (such as bats or birds)Steelman, C.D. 2000
Biology and control of bed bugsArchive
''Cimex lectularius'', in poultry houses. Avian Advice 2: 10,15. that may also harbour bed bugs or related species such as the bat bug;
* People visiting an infested area (e.g. dwelling, means of transport, entertainment venue, or lodging) and carrying the bugs to another area on their clothing, luggage, or bodies. Bedbugs are increasingly found in air travel.

Though bed bugs will opportunistically feed on pets, they do not live or travel on the skin of their hosts, and pets are not believed to be a factor in their spread.

Diagnosis

A definitive diagnosis of health effects due to bed bugs requires a search for and finding of the insect in the sleeping environment as symptoms are not sufficiently specific. It is difficult to distinguish bed bug bites from other arthropod bites and the linear pattern of bites (known colloquially as "breakfast, lunch and dinner" bites) is not specific for bed bugs. If the number in a house is large a pungent sweet odour may be described. There are specially trained dogs that can detect this smell.

Detection

Bed bugs can exist singly but tend to congregate once established. Although strictly parasitic, they spend only a tiny fraction of their lives physically attached to hosts. Once a bed bug finishes feeding, it follows a chemical trail to return to a nearby harborage, commonly in or near beds or couches, where they live in clusters of adults, juveniles, and eggs. These places may include luggage, vehicle interiors, furniture, bedside clutter—even inside electrical sockets or laptop computers. Bed bugs may also lodge near animals that have nested within a dwelling, such as bats, birds, or rodents. They are also capable of surviving on domestic cats and dogs, though humans are the preferred host of ''C. lectularius''.
Bed bugs can also be detected by their characteristic smell of rotting raspberries. Bed bug detection dogs are trained to pinpoint infestations, with a possible accuracy rate between 11% and 83%.

Homemade detectors have been developed. Bedbug detectors, often referred to as "monitors", "traps" or "interceptors", use attractant based methods such as lactic acid or carbon dioxide (associated with the presence of a human body) or pheromones to trap bugs in a container. Bedbug detectors can confirm a bedbug infestation but they are not effective for eradication.

File:Bedbugs1.jpg, Eggs and two adults found inside a dresser
File:BedBugFeces.jpg, Fecal spot
File:Bed Bug On Carpet.jpg, Bed bug on carpet

Differential diagnosis

Other possible conditions with which these conditions can be confused include scabies, gamasoidosis, allergic reactions, mosquito bites, spider bites, chicken pox and bacterial skin infections.

Prevention

To prevent bringing home bed bugs, travelers are advised to take precautions after visiting an infested site: generally, these include checking shoes on leaving the site, changing clothes outside the house before entering, and putting the used clothes in a clothes dryer outside the house. When visiting a new lodging, it is advised to check the bed before taking suitcases into the sleeping area, and putting the suitcase on a raised stand to make bedbugs less likely to crawl in. An extreme measure would be putting the suitcase in the tub. Clothes should be hung up or left in the suitcase, and never left on the floor. Additional preventative measures include sealing cracks and crevices (which are often the sites of bed bug harborages), inspecting furniture, and for exposed travelers to decontaminate clothes and luggage upon returning home. The founder of a company dedicated to bedbug extermination said that 5% of hotel rooms he books into were infested. He advised people never to sit down on public transport; check office chairs, plane seats, and hotel mattresses; and monitor and vacuum home beds once a month. Close all wall openings or gaps; bed bugs tend to hide in dark places and cracked walls are a perfect spot for them to infest.

Management

Treatment of bed bug bites requires keeping the person from being repeatedly bitten, and possible symptomatic use of antihistamines and corticosteroids (either topically or systemically). There however is no evidence that medications improve outcomes, and symptoms usually resolve without treatment in 1–2 weeks.

Avoiding repeated bites can be difficult since it usually requires eradicating bed bugs from a home or workplace; eradication is most effective using non-chemical control methods. Non-chemical control methods include vacuuming carpet and furniture (often with scraping) into a disposable bag which is then sealed into a plastic bag to prevent re-infestation. Other methods include removing textile materials from an area and washing them in hot water (at least 60 degrees Celsius) or freezing them at . Most consumer-grade freezers are inadequate to kill bedbugs because they cannot create sufficiently low temperatures. Unremovable textiles such as mattresses can be steamed to at least and this method can penetrate deep into the textile to effectively kill bed bugs in, potentially, under one minute. Heating tents or chambers can be used for infested materials or entire rooms can be heated to at least to effectively eradicate infestation.

There is no evidence to indicate that a combination of non-chemical methods plus insecticides is more effective than non-chemical methods alone with regards to eradication of bed bug infestations.

Insecticides are mostly ineffective for the eradication of bedbug infestations as most bedbugs are resistant to insecticides, including pyrethroids which are found in approximately 90% of commercial grade insecticides. Furthermore, insect foggers (known as "bug bombs") are ineffective in the eradication of bed bug infestation as they are unable to penetrate bed bug harborages. Resistance to pesticides has increased significantly over time, and there are concerns about harm to health from their use.

Once established, bed bugs are extremely difficult to get rid of. Bed bugs are particularly difficult to eradicate in apartment complexes as harbors can exist in other areas of the building when single units are treated.

Mechanical approaches, such as vacuuming up the insects and heat-treating or wrapping mattresses, are effective. An hour at a temperature of or over, or two hours at less than kills them. This may include a domestic clothes drier for fabric or a commercial steamer. Bed bugs and their eggs will die on contact when exposed to surface temperatures above and a steamer can reach well above . A study found 100% mortality rates for bed bugs exposed to temperatures greater than for more than 2 minutes. The study recommended maintaining temperatures of above for more than 20 min to effectively kill all life stages of bed bugs, and because in practice treatment times of 6 to 8 hours are used to account for cracks and indoor clutter. This method is expensive and has caused fires. Starving bedbugs is not effective, as they can survive without eating for 100 to 300 days, depending on temperature.

that no truly effective insecticides were available. Insecticides that have historically been found effective include pyrethroids, dichlorvos, and malathion. Resistance to pesticides has increased significantly in recent decades. The carbamate insecticide propoxur is highly toxic to bed bugs, but it has potential toxicity to children exposed to it, and the US Environmental Protection Agency has been reluctant to approve it for indoor use. Boric acid, occasionally applied as a safe indoor insecticide, is not effective against bed bugs because they do not groom.

Epidemiology

Bed bugs occur around the world. Before the 1950s about 30% of houses in the United States had bedbugs. This percentage has since fallen, which is believed to be partly due to the use of DDT to kill cockroaches. The invention of the vacuum cleaner and simplification of furniture design may have also played a role in the decrease. Others believe it might simply be the cyclical nature of the organism.

However, rates of infestation in developed countries have increased dramatically since the 1980s. This is thought to be due to greater foreign travel, increased immigration from the developing world to the developed world, more frequent exchange of second-hand furnishings among homes, a greater focus on control of other pests, resulting in neglect of bed bug countermeasures, and increasing bedbug resistance to pesticides. Lower cockroach populations due to insecticide use may have aided bed bugs' resurgence, since cockroaches are known to sometimes prey on them. Steadily-rising resistance to DDT and other potent pesticides may have also contributed; bans on DDT may have contributed as well, though studies have shown resistance continued to rise in countries where they continued to be used.

The U.S. National Pest Management Association

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