Cimex lectularius

Cimex lectularius
Adult
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hemiptera
Suborder:	Heteroptera
Family:	Cimicidae
Genus:	Cimex
Species:	C. lectularius
Binomial name
Cimex lectularius Linnaeus, 1758

Cimex lectularius is a species of Cimicidae. Its primary hosts are humans, and it is one of the world's major "nuisance pests".

Although bed bugs can be infected with at least 28 human pathogens, no studies have found that the insects are capable of transmitting any of these to humans.^[1] They have been found with methicillin-resistant Staphylococcus aureus (MRSA)^[2] and with vancomycin-resistant Enterococcus faecium (VRE), but the significance of this is still unknown.^[3]

Investigations into potential transmission of HIV, MRSA, hepatitis B, hepatitis C, and hepatitis E have not shown that bed bugs can spread these diseases. However, there is some evidence that arboviruses may be transmissible.^[4]

Bed bug bites or cimicosis may lead to a range of skin manifestations from no visible effects to prominent blisters.^[5] Effects include skin rashes, psychological effects, and allergic symptoms.^[6]

Occurrence and distribution[edit]

Cimex lectularius is found all over the world in almost every area that has been settled by humans. In the past, bed bugs were particularly an affliction of the poor and occurred in mass shelters. However, in the early part of the modern resurgence it was the tourist areas that were impacted. Today, bed bugs have conquered quite diverse locations, ranging from hospitals and hotels, to trains, cruise ships and even airplanes. Most commonly, bed bugs travel as stowaways in luggage, although they can be transferred via furnishing and other belongings, as well by spreading to adjoining properties. Since there are no mandatory reporting requirements, exact figures on the occurrence of bed bugs are unknown and, due to the stigma often associated, many infestations are simply not reported.^[7]

Life cycle[edit]

If feeding regularly, a female bed bug can lay between two and three eggs per day throughout her adult lifetime, which may last several months, allowing one female to produce hundreds of offspring under optimal conditions. The tiny (<1 mm) yellowish-white eggs are vase-shaped and are laid within harborages where the insects rest between blood meals and spend virtually all of their time: although parasitic, they do not reside on their hosts and only contact them briefly for blood meals. Eggs typically hatch within 10 days at room temperature, but become non-viable below 14 °C (57 °F). Cimex lectularius goes through five immature life stages that each require a blood meal to develop and move on to the next stage. The life cycle occurs more rapidly at warmer temperatures, and more slowly at lower ones. Once the egg hatches, the larval form must take one blood meal per week as it completes each of its five to six molts. Once it completes the final molt, it will have reached the adult stage and can reproduce. Meals take several minutes to consume, and occur only under the correct conditions: darkness, warmth, and carbon dioxide. C. lectularius typically feed on hosts when they are asleep, they tend to feed exclusively on humans, and are obligate blood feeders. Newly hatched nymphs must consume a blood meal within two to three days or will die of starvation, whereas an adult can live for as long as six months between feedings.^[8]

Parasitic life style and blood feeding is characteristic of both adult sexes as well as the larval stage. They live at night and during the day they hide in wall crevices, under wallpaper, in furniture grooves, books, clothes, beds, electronics, in darkened and warm places, in bird and animal cages; however, they can also attack during the day if they are very hungry. Bed bugs do not have a nest of sorts, as ants do, but they tend to congregate in safe places near a food source. These places can be visually identified by dark patches of insect excrement, along with which their eggs and larval exuviae can be found. Bed bugs live well in most areas, regardless of their state of sanitation. Bed bugs emerge from their shelter in the dark and attack (suck blood on exposed parts of the body), usually at 3-8 a.m. Bed bugs feed exclusively on blood.^[9]

The average lifespan of bed bugs is between 99 and 300 days in a laboratory, we do not know how long a bed bug might live in a home environment. In the absence of food, bed bugs may go into a state similar to anabiosis, in which, at sufficiently low ambient temperatures, they remain viable for more than one year. Females are capable of laying around 1-7 eggs in a 10 day period after a single blood meal producing around 113 in her entire lifespan.^[10] In unfavourable conditions, bed bugs are able to migrate between rooms along ventilation ducts and, in summer, along the outside walls of houses. An adult bedbug travels more than 1 m in one minute, while a nymph travels up to 25 cm.

Bed bugs have an excellent sense of smell and drink blood during all phases of development. The larva has to drink a full portion of blood to pass on to the next instar; only then can another molt take place. The first instar larva drinks about 1/3 mg of blood per blood-sucking session; subsequent instars respectively more; the adult female drinks up to 7 mg.^[11] Usually feeds regularly every 5-10 days, mainly on human blood, but may also attack pets, birds, rats and mice. In rural areas, they often crawl from infested poultry houses to households.

Resistance[edit]

Some populations have evolved resistance to insecticides.^[12] Seong et al., 2010 find deltamethrin resistance provided by an allele – L925I – of the voltage gated sodium channel.^[13] Seong et al. also find a dose–response relationship of resistance to L925I copy number.^[13]

References[edit]