Bed bugs
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Bed bugs are blood‑sucking insects that are closely associated with humans. Due to resistance to insecticides and increased travel activity, the prevalence of bed bugs has risen sharply across large parts of the world since the turn of the millennium.
Prevalence
Bed bugs (Cimex lectularius) are blood-sucking insects that primarily feed on humans. The species is found indoors worldwide, but mainly in cooler regions (1) and in recent years has become much more common in Norway (2).
A close relative, the tropical bed bug (Cimex hemipterus), which also primarily feeds on humans, is also found globally, but more commonly found in tropical regions. This species has only been found once in Norway.
Leptocimex boueti is the third species that primarily attacks humans, but it is only found in Africa (3).
In Norway, bat bugs (Cimex pipistrelli group) and swallow bugs (Cimex hirundinis) can also occasionally enter indoors and bite humans.
Characteristics
Bed bugs are reddish-brown with an oval, flat body shape (Figure 1). Adults are 5–6 mm long and 3 mm wide. The nymphs resemble adults, but they are smaller and lighter in colour. The eggs are 1 mm long and white (figure 2). When bedbugs feed on blood, they swell up and become darker in color (Figure 3). They have no wings and their mouth parts form a long, articulated suction tube (proboscis) which is pointed backwards under the head and thorax when not in use. The proboscis points forward when in use.
In addition to the appearance of the animal itself, bed bugs secrete an alarm pheromone with a characteristic odour that can be prominent in rooms with many animals (4;5). In well-established infestations, one will also easily find excrement stains around hiding places. These appear as small black, brown, or light gray spots. The gray spots fluoresce under UV light (385 nm).
Life cycle
Bed bugs are bloodsuckers, and their reproduction and development are highly dependent on temperature and availability of food (3;6). They lay 5–8 eggs per week at 23 °C (7) and can produce up to 200 eggs during their adult life. The eggs are glued to the substrate in the bedbugs' hiding places. It takes 4–21 days for a nymph to hatch from the egg. Nymphs have five developmental stages, and they must feed on blood at least once between each stage (8).
At room temperature (22 °C), the entire life cycle takes about 2 months (6). At low temperatures, the development time can be one year. Activity stops when the temperature drops below 10 °C. Bedbugs can survive without food for a long time. At 10 °C, adults have survived without blood for 485 days, while the smallest nymphs can survive for up to nine months (9). Although bedbugs are closely associated with humans, they can also feed on other mammals (bats, cats, and dogs, etc.) and birds (6).
Bed bugs feed on blood
Bed bugs usually bite humans at night and preferably suck blood from exposed skin - areas not covered by clothing. An adult bed bug feeds on blood for 5–20 minutes (5). After the meal, it quickly crawls back to its hiding place where digestion, skin-shedding, and egg-laying occurs. Their characteristic brown-black excrement can usually be found here too (Figure 4). At room temperature, and with regular access to food, bed bugs will feed weekly.
The bites themselves can be very irritating, and excessive scratching of the bite sites can lead to secondary bacterial infections (6). There is a great individual difference in people's sensitivity to bed bug bites. Some develop strong, itchy marks and weals, while others have minor or no reaction. The reaction to bites can appear immediately or after some time. With repeated biting episodes, the reaction may occur more quickly and become stronger (6;10;11).
It is not known whether bed bugs transmit diseases to humans. A number of pathogenic microorganisms have been found in bed bugs that have fed on the blood of infected humans (12), but only Trypanosoma cruzi, which causes Chagas disease, has been shown to survive for a long time in laboratory cultures of bed bugs and to be transmitted to rats (13). This entails a small risk of transmission of this parasite from bed bug feces to wounds in human skin, but there is no documentation that this type of transmission occurs in natural bed bug infestations.
Psychological strain
The psychological strain of having bed bugs in the home is significant for many. In addition to bothersome bites, sleep deprivation and an increased risk of anxiety and depression may occur (14). There is also often the burden of having to pay for relatively expensive extermination to get rid of the pests (15). Bedbugs can affect lower socioeconomic groups more severely. This is often due to a lower ability to bear the high costs associated with effective extermination, which results in a longer duration of the problems (16–18).
Spread
Bed bugs can travel with luggage, used furniture, other household items and used bed linen (4; 19; 20). They are usually found in places with a high turnover of guests, such as hotels, cabins, youth hostels and student accommodation. Bed bugs may then be transported to new accommodation or private homes. Once bed bugs have established themselves in a room, they can spread to other rooms or apartments in the same building (21).
Prevention
Travel
The most common way to get bedbugs into the home is via luggage after staying at places with bed bugs (4;19).
Take these precautions when traveling:
- Check the underside of the bed at your accommodation for excrement and bed bugs. It is especially important to check cracks and lift textile edges in the bed where possible. To ensure good lighting during the inspection, one can, for example, use the flashlight app on a mobile phone. If you see bed bugs or if you suspect there are traces of them, do not move into the room. Contact the reception immediately and ask them to examine the room carefully. Request a new room or move to different accommodation if you are in doubt.
- Keep as much of the belongings in the suitcase or bags at all times to prevent bed bugs from getting into the luggage. Only what is needed at the moment should be taken out and returned to the luggage after use. Bed bugs are often brought into the residence in luggage that has been in accommodation infested with bed bugs.
- Place the suitcase away from the bed, preferably on a luggage rack if one is available, to reduce the chance of bed bugs entering the luggage. Placing your luggage in the bathroom is a good idea since bed bugs are unlikely to be there.
- Take precautions when coming home. If you have stayed at a place where you suspect there may have been bed bugs, cold or heat treatment of the luggage will kill any individuals and eggs (see more under Control below) and prevent them from being brought in upon returning home.
The Norwegian Institute of Public Health in cooperation with the Norwegian Hospitality Association have published a guideline Bedbugs - Information and advice for providers of overnight accommodation. The guideline describes routines and how to handle bed bug problems in the tourism industry.
Used items
Second-hand furniture (beds, mattresses, sofas, chairs, etc.) may contain bed bugs. Examine these objects thoroughly before taking them home. Freezing or heat treating the object can also be considered.
Brief visits
It is unlikely that bed bugs will be found in clothing or other items after day visits to affected locations. However, if there are many insects present, there is a certain risk that bed bugs can crawl into bags and shoes. Take minimal belongings into the residence and place them away from beds and furniture.
Inspection
To detect or combat bed bugs, it is important to be aware of their hiding places. They primarily stay where people sleep (in bed, sofa, and armchair) and hide in cracks and small cavities. However, bed bugs can also be present quite far from the bed (25). Examples of such hiding places are the back of cabinets and pictures, near curtains, in cracks in paneling, behind moldings at floors, ceilings, doors or windows, behind loose wallpaper, in electrical outlets and appliances, behind wires, or at pipe penetrations (4).
At the hiding places, one can find signs such as empty skins, eggs, and droppings in addition to live and dead individuals. The black spots of the droppings are often the easiest to find, which is why it is wise to look for these on different parts of the bed (24). Especially on the underside and under fabric edges, there can be a good chance of seeing such traces if there are bed bugs in the room. Blood stains on sheets can also be an indication of bed bugs since they can leave some blood right after a blood meal. If bed bugs are discovered during an inspection, it is important to inspect all adjacent living units in the same building since the animals may have spread to many rooms and apartments (22;24).
If bed bugs are detected early after they have established themselves in a room, control will be relatively simple because there are few animals that usually stay in or near the bed in a room. If, on the other hand, an early inspection is not carried out, the bed bugs can become numerous and spread throughout the building. Control will then become much more complicated and costly (24).
Combating bed bugs – Building-wide, IPM, and Non-toxic
When combating bedbugs in a building, it is best to use a building-wide and integrated pest management (IPM) approach. Better results are achieved when the entire building is considered as a treatment unit (i.e., building-wide) since bed bugs may have spread to several rooms and apartments from where they first established. It will not be sufficient to combat pests in only one apartment if neighboring apartments are also infested. Bed bugs can migrate back and cause reinfestation even if the treated apartment is pest-free for a period (16;22–24).
Effective bed bug control is difficult and professional help is advised. Several different control methods should be combined to increase the probability of a successful outcome. When bed bugs are discovered in hotels, student accommodation, apartment blocks and other large properties, control methods should be co-ordinated for a successful result.
An IPM approach means a holistic, knowledge-based control which includes thorough inspection of all possible infested locations as well as performing a sufficient number of different control measures adapted to the situation in the specific case. In addition, it is important to carry out follow-up inspections after some time to confirm that the infestation has been removed (18;22). For bed bug control, traditional chemical insecticides will not work since there is a high degree of resistance to these (28). These agents also pose a health risk in an indoor environment (6). By using non-toxic methods, one will therefore achieve both more effective and safer control.
Methods that work against bedbugs
Information and coordination
Both before and during an eradication, it is advantageous if as many affected parties in the building as possible are informed about what bed bugs are, what the risk of spreading is, and what will happen during the eradication itself. This will create an understanding of the control measures, reduce the risk of disagreements, and result in more satisfied residents (22;26).
By coordinating measures at a more overarching level, e.g., through a housing cooperative, it will be easier to have the necessary oversight of the eradication. It is common for multiple residential units to encounter bed bug problems when an infestation first occurs in apartment buildings, student housing, hotels, and other larger properties. Building-wide measures are therefore crucial for rapid eradication success. By having a coordinated and systematic approach, the total eradication costs will also be reduced (16).
Professional help: effective bedbug control is difficult to carry out, and it is advantageous to seek help from professional pest controllers. This is partly because it is often necessary to combine several different control methods to increase the chances of a successful result.
Sealing
The biology of bed bugs makes eradication difficult. They can survive for a long time without food, have many hiding places, and can move between rooms and apartments (3). Sealing cracks and other small openings will reduce the number of hiding places and increase the likelihood of successful control (27).
Vacuuming
Thorough vacuuming is a useful tool for removing as many bugs as possible. This alone rarely provides complete control (6;27). To prevent the spread of bugs from the vacuum bag, it is important that it is destroyed after use.
Cold treatment
An effective cold treatment that kills eggs, nymphs, and adult bed bugs involves freezing items at -18°C for 3 days. The freezing period needs to be long enough for the items to reach this temperature throughout for 3 days. Freezer rooms or freezers can be used (27;29). If -18°C is not achieved, the freezing period is extended. For example, bed bugs need to be exposed to -7°C for 3 weeks in order to die (30). Infected objects that are transported for cold treatment elsewhere or to a landfill for disposal need to be wrapped in tight plastic so that animals do not have the opportunity to spread during transit.
Heat Treatment
Heat treatment of objects can be carried out in a sauna, drying cabinet, tumble dryer, or special tent made for bed bug treatment. The temperature needs to be above 50°C for two hours. Here too, there is a need for objects to be treated long enough to reach the desired temperature throughout for a sufficient amount of time (27). Lower temperatures can also kill bed bugs, but then the treatment time needs to be increased. At 40°C, bed bugs will die after 2 days (31). Washing in a washing machine at a minimum of 60°C is also an effective treatment option (32).
Heat treatment of entire rooms or buildings can also be used. The treatment is labor- and energy-intensive, but if a high enough temperature is achieved and all animals and eggs are exposed for a sufficiently long time, the bed bugs will be killed (27;33;34).
Heat treatment using steam on bed frames, mattresses, sofas, smaller cavities, behind moldings, and in cabinet bases can be carried out with steamer machines that blow out steam. Special devices have been developed that produce water vapor at suitable pressure and temperature, but a regular steam cleaner can also be used in many cases (27;35). The temperature immediately after the steamer head has passed the bed bugs should be at least 70°C (27). Steam treatment will be effective in treating the surface of objects, but will work poorly on bed bugs that are inside objects such as a mattress or in an insulated wall.
The materials to which the steam is applied must be able to withstand 100°C. It is also important to ensure that there is not too much moisture in cavities being steam-treated, as this can cause moisture damage. It is also important to avoid using steam near power outlets and electrical appliances.
Desiccant Powder
Silica powder (silica gel) or diatomaceous earth can be used in bed bug control. These two types of powder kill upon contact between the bed bugs and the desiccant powder. The bed bugs sustain damage to their insect cuticle and dry out quickly due to increased water evaporation from the body. A thin layer of powder should be applied in strategic places where the bed bugs pass. It has also been shown that animals that have been covered with powder can transfer it to others that have not walked on surfaces with powder themselves (36).
Survival after exposure to different types of desiccant powder at a dosage of 1.5 g/m². Amorphous SiO2 (Sylloid244FP (powder), Cimexa (powder), and For Bug Plus (spray)) provides faster and more complete mortality compared to crystalline SiO2 (InsektNix (powder), DE-powder (powder), and InsektNix (spray)).
The correct amount (dose) is important for good effect since doses that are too high can scare away the bed bugs and thereby prevent the desired contact between the desiccant powder and the bed bugs. Silica gel (amorphous SiO2) is more effective than diatomaceous earth (crystalline SiO2) at both high and low doses (36;37 and figure). At the same dose (g/m2) and exposure time, one will therefore achieve faster and more complete mortality by using the former. Silica gel is available both as loose powder and in spray cans. At appropriate doses (1.5 g/m2), the effect from the spray formulation is practically the same as the effect from loose powder. Factors such as application area, type of surface, local working conditions, health effects, and regulations will therefore determine how and which desiccant powder is used.
Follow-up inspection
After a treatment has been carried out, it is important to be aware of any recurrence of bed bugs. Recurrence is prevented by regular inspections over some time after the treatment has ended. One looks for fresh, live fecal spots and live insects and monitors whether problems with bites have disappeared. Bed bug traps can also be used to monitor the bed bug situation. ClimUp or similar traps that catch bed bugs moving around have proven effective for this purpose (24).