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, chronic  or severe infestation may lead to anemia. Bacterial skin infection may occur due to skin break down 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. Similar to humans, bed bugs can feed on other warm -blooded animals 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: 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, vehicles 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" or "traps", 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. 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 due to  not having low enough temperatures. Unremovable textiles such as mattresses can be steamed at least and this method can penetrate deep into the textile to effectively kill bed bugs quickly (under 1 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. 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 predate 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 reported a 71% increase in bed bug calls between 2000 and 2005. The number of reported incidents in New York City alone rose from 500 in 2004 to 10,000 in 2009. In 2013, Chicago was listed as the number one city in the United States for bedbug infestations. As a result , the Chicago City Council passed a bed bug control ordinance to limit their spread. Additionally, bed bugs are reaching places in which they never established before, such as southern South America. The rise in infestations has been hard to track because bed bugs are not an easily identifiable problem and is one that people prefer not to discuss. Most of the reports are collected from pest-control companies, local authorities, and hotel chains. Therefore, the problem may be more severe than is currently believed. Species. The common bed bug ("Cimex lectularius") is the species best adapted to human environments but  is also known from birds, Chiroptera, "Gallus" (chickens and relatives), "Myotis myotis", and sheep ("Ovis aries"). It is found in temperate climates throughout the world. Other species include "C. hemipterus", found in tropical regions, which also infests poultry (including "Gallus") and bats, and "Leptocimex boueti", a relative of "C. lectularius" adapted for the tropics of West Africa and South America, which infests bats and humans. "C. pilosellus" and "C. pipistrella" primarily infest bats, while "Haematosiphon inodora", a species of North America, primarily infests poultry. Evolution. Cimicidae, the ancestor of modern bed bugs, first emerged approximately 115 million years ago, more  than 30 million years before bats—their previously presumed initial host—first appeared. From unknown ancestral hosts, a variety of different lineages evolved which specialized in either bats or birds. The common ("C. lectularius") and tropical bed bug ("C. hemipterus"), split 40 million years before "Homo" evolution. Humans became hosts to bed bugs through host specialist extension (rather than switching) on three separate occasions. History. Bed bugs were mentioned in ancient Greece as early as 400 BC, and were later mentioned by Aristotle. Pliny's "Natural History", first published "circa" AD 77 in Rome, claimed bed bugs had medicinal value  in treating ailments such as snake bites and ear infections. Belief in the medicinal use of bed bugs persisted until at least the 18th century, when Guettard recommended their use in the treatment of hysteria. Bed bugs were first mentioned in Germany in the 11th century, in France in the 13th century, and in England in 1583, though they remained rare in England until 1670. Some in the 18th century believed bed bugs had been brought to London with supplies of wood to rebuild the city after the Great Fire of London (1666). Giovanni Antonio Scopoli noted their presence in  Carniola (roughly equivalent to present-day Slovenia) in the 18th century. Traditional methods of repelling and/or killing bed bugs include the use of plants, fungi, and insects (or their extracts), such as black pepper; black cohosh ("Actaea racemosa"); "Pseudarthria hookeri"; "Laggera alata" (Chinese "yángmáo cǎo" | 羊毛草); "Eucalyptus saligna" oil; henna ("Lawsonia inermis" or camphire); "infused oil of "Melolontha vulgaris"" (presumably cockchafer); fly agaric ("Amanita muscaria"); tobacco; "heated oil of Terebinthina" (i.e. true turpentine); wild mint ("Mentha arvensis"); narrow-leaved pepperwort ("Lepidium ruderale"); "Myrica" spp. (e.g. bayberry); Robert geranium ("Geranium robertianum"); bugbane ("Cimicifuga" spp.); "herb and seeds of "Cannabis""; "opulus  berries (possibly maple or European cranberrybush); masked hunter bugs (Reduvius personatus"), "and many others". In the mid-19th century, smoke from peat fires was recommended as an indoor domestic fumigant against bed bugs. Dusts have been used to ward off insects from grain storage for centuries, including plant ash, lime, dolomite, certain types of soil, and diatomaceous earth or Kieselguhr. Of these, diatomaceous earth in particular has seen a revival as a nontoxic (when in amorphous form) residual pesticide for bed bug abatement. While diatomaceous earth often performs poorly, silica gel may be effective. Basket-work panels were put around beds  and shaken out in the morning in the UK and in France in the 19th century. Scattering leaves of plants with microscopic hooked hairs around a bed at night, then sweeping them up in the morning and burning them, was a technique reportedly used in Southern Rhodesia and in the Balkans. Bean leaves have been used historically to trap bedbugs in houses in Eastern Europe. The trichomes on the bean leaves capture the insects by impaling the feet (tarsi) of the insects. The leaves are then destroyed. 20th century. Before the mid-20th century, bed bugs were very common. According to  a report by the UK Ministry of Health, in 1933, all the houses in many areas had some degree of bed bug infestation. The increase in bed bug populations in the early 20th century has been attributed to the advent of electric heating, which allowed bed bugs to thrive year-round instead of only in warm weather. Bed bugs were a serious problem at US military bases during World War II. Initially, the problem was solved by fumigation, using Zyklon Discoids that released hydrogen cyanide gas, a rather dangerous procedure. Later, DDT was used to good effect, though bedbugs have  since become largely resistant to it. The decline of bed bug populations in the 20th century is often credited to potent pesticides that had not previously been widely available. Other contributing factors that are less frequently mentioned in news reports are increased public awareness and slum clearance programs that combined pesticide use with steam disinfection, relocation of slum dwellers to new housing, and in some cases also follow-up inspections for several months after relocated tenants moved into their new housing. Society and culture. Legal action. Bed bugs are an increasing cause for litigation. Courts have, in some cases, exacted  large punitive damage judgments on some hotels. Many of New York City's Upper East Side homeowners have been afflicted, but they tend to remain publicly silent in order not to ruin their property values and be seen as suffering a blight typically associated with the lower classes. Local Law 69 in New York City requires owners of buildings with three or more units to provide their tenants and potential tenants with reports of bedbug history in each unit. They must also prominently post these listings and reports in their building. Research. Bed bug secretions can inhibit the growth of  some bacteria and fungi; antibacterial components from the bed bug could be used against human pathogens, and be a source of pharmacologically active molecules as a resource for the discovery of new drugs.