US Pharm. 2012;37(8):47-50.
Bed bugs have been a known human pest for thousands of
years. They are small, wingless insects with a flat body that is ideal
for hiding in cracks and crevices in headboards, mattresses, and box
springs. They feed exclusively on the blood of humans or warm-blooded
animals. Their bites can elicit various cutaneous and systemic reactions
in humans and are generally treated symptomatically. Bed bugs can be
very difficult to eradicate since they have developed resistance to many
chemical treatments. Not only can bed bugs create an emotional effect,
but they have a significant impact on public health.
Epidemiology
The common bed bug, Cimex lectularius, was nearly
eradicated from developed countries in the 1940s, but within the last 10
years the United States and Canada have seen a rapid resurgence in bed
bug infestations.1 A 2008 online survey of pest control
professionals determined that in the past 2 years, 91% of respondents
had encountered bed bugs. In the past 5 years, 37% of respondents had
encountered bed bugs, while in the past 10 years, only 21% had
encountered bed bugs.2 According to data from Terminix, the most bed bug–infested U.S. cities in 2012 were Philadelphia, Cincinnati, and New York.3
This recent resurgence may be attributed to increased rates of
international travel, immigration, changes in pest control practices,
and insecticide resistance. Outbreaks occur in a wide variety of
settings and most often occur in single-family homes, apartments,
hotels, shelters, college dormitories, and nursing homes.4
Risk factors for bed bug infestations include rapid turnover of
residents, increased population density, and frequent relocation.
Unsanitary conditions and the number of people in a household are not
the best indicators for the presence of bed bugs, and outbreaks are
generally not specific to any geographic areas or climate conditions.5
Entomology
Cimex lectularius is wingless, flat, oval-shaped
insect that feeds exclusively on the blood of humans or warm-blooded
animals. It is attracted to warmth and carbon dioxide, and most Cimex species
feed on humans, bats, or birds. Newly hatched bed bugs are about 1 mm
long and are colorless to cream colored. Adult bed bugs are about 5 mm
when unfed (about the size of an apple seed) and are a deep brown or
reddish brown color. After feeding, bed bugs become engorged and are
dull red in color. A female will lay approximately 200 to 500 eggs
during her lifetime, and the typical lifespan is about 10 months.6
Bed bugs are mostly nocturnal, and they tend to hide
during the day. Their tiny, flat bodies are ideal for hiding in crevices
in mattresses, box springs, bed frames, and headboards. They can move
swiftly with their legs over floors, walls, and ceilings. They feed
about every 3 to 7 days and do not remain on their hosts between
feedings.6 During feedings, they generally attach to their host for about 10 to 20 minutes.5
Bed bugs can spread by either active or passive dispersal.
Active dispersal occurs when a bed bug uses its legs to walk a short
distance to a new location. Bed bugs do not fly or jump. They are rapid
crawlers, similar in speed to an ant. A bed bug may spread between rooms
in infested buildings this way. Passive dispersal is when a bed bug is
transported on clothing, luggage, furniture, and other objects. Bed bugs
have been discovered on travelers in airplanes, cars, trains, and
ships, as well as on travelers on foot.5
Detection
Due to their elusive nature, detection of bed bugs can be
very difficult. Bed bug infestation should be suspected if dark brown or
reddish brown fecal and blood spots are found on clothing, mattresses,
bedding, or furniture. In addition, bed bugs can emit a characteristic
sweet, musty smell. Patients may present with itching or skin irritation
with bed bug bites, but not everyone has a reaction to the bites. These
bites may be confused with bites from other creatures such as
mosquitoes, spiders, and fleas. Bed bug infestation is confirmed by the
presence of live or dead bugs or their eggs. Every crack and crevice in
living areas must be searched extensively to confirm the presence of bed
bugs. Using a flashlight about an hour before dawn is a good way to
detect bed bugs because they are more active during that time.7
Bed bug infestations are not just limited to the bed. They
prefer wood, paper, and fabric surfaces in dark and isolated areas. Bed
bugs have been found in a wide variety of places including bed frames,
door frames, headboards, telephones, furniture, loose wallpaper, wall
cracks, drapery, clothing, and movie theater seats. Bed bug–detecting
dogs have also been employed to discover bed bugs via scent.6 A properly trained dog can detect a single live bed bug with 96% accuracy.8
Clinical Presentation
Bed bugs are equipped with mouthparts that are ideal for
feeding on blood. During feeding the bed bug injects saliva, which
contains an anesthetic and an anticoagulant that can prevent the host
from feeling the bite. However, some people do experience a painful
bite. The saliva also contains proteins that can elicit various
responses from the host. Reactions to the bites can occur immediately,
several days later, or not at all. It is most commonly quoted that 20%
of people will not react to bed bug bites.9 However, a recent
study determined that 11 out of 24 people experienced no reaction to a
first bite and that 18 out of 19 people developed a reaction upon
subsequent bites.9 This suggests that hosts can become sensitized after repeated exposure.
Bites are typically located on skin that is exposed while sleeping such as the face, arms, and legs.10
They may appear in a random formation or in a straight line, and the
number of bites usually depends on the severity of the infestation.11
Cutaneous responses from bed bug bites can vary greatly. Typically,
bites present as erythematous and maculopapular skin lesions that are
about 2 to 5 mm in diameter. There is often a hemorrhagic crust or
vesicle at the center of the lesion. The bites often look very similar
to a mosquito or flea bite and are associated with itching and
inflammation. The skin lesions last about 2 to 6 weeks and are usually
self-limiting. More complex skin reactions may present as local
urticaria and bullous rashes. Scratching the skin lesions can lead to
secondary infections and ulcerations.
Although uncommon, systemic reactions from bed bug bites
have been reported. These reactions include generalized urticaria,
asthma, and, in very rare cases, anaphylaxis. The blood loss a host
experiences during a bite typically does not adversely affect the host.6 However, there have been rare reports of iron deficiency anemia with severe infestations.10 Mental health issues such as anxiety and insomnia have also been reported in people living in bed bug–infested homes.11
Transmission of Disease
Investigators have theorized for many years that bed bugs
may serve as vectors for transmission of disease. In order for a bed bug
to do this, many steps would need to occur. The insect would have to be
able to acquire an infectious pathogen, maintain it, and then be able
to transmit it to another organism. Over 45 different pathogens have
been suspected to be carried by bed bugs, including HIV and hepatitis B.1 Vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) have been reportedly isolated from bed bugs as well.12
Although bed bugs may have the ability to carry many pathogens, at this
time there is not a single proven case of bed bug transmission of
disease to humans. Further investigations are necessary to determine if
bed bugs play a role in disease transmission.
Eradication
Bed bugs are extremely difficult to eradicate. Elimination
can be challenging because bed bugs are very hard to locate and are
resistant to many pesticides. Local public health departments may also
have limited resources to help exterminate pests. A multifaceted
approach is necessary for complete eradication. Goddard and deShazo
outline five steps for the successful eradication of bed bugs: “1)
proper identification of the bed bug species present; 2) education of
persons involved; 3) thorough inspection of infested and adjacent areas;
4) implementation of chemical and nonchemical control measures; and 5)
follow-up to evaluate the success of eradication.”13
When bed bugs are suspected or identified, a licensed pest
control professional should be consulted. A combination of chemical and
physical removal is usually necessary for complete eradication.
Oftentimes multiple rounds of physical and chemical removal will be
needed to eradicate bed bugs from an infested site.
Physical Eradication: Removal and
disposal of infested furniture and mattresses may be necessary if the
infestation is severe. For less severe infestations, bed bugs can be
removed with vacuuming. It is usually necessary to scrape bed bugs with
the suction end of the vacuum to remove them. Routine vacuuming may not
be particularly effective at removing bed bugs because they cling
tightly to many surfaces. Vacuuming should be performed every day or
every other day until the infestation is gone. The vacuum bag should be
removed, properly sealed in a secondary bag, and placed in an outside
dumpster. Once a vacuum is used for removal of bed bugs, it should only
be used for that purpose. After bed bugs are removed from a mattress, it
can be sealed in a mattress encasement or cover. This will trap any
remaining bed bugs inside the cover. It is important to keep the
mattress cover sealed for at least 1 year because bed bugs can survive
up to a year without a blood meal.6 Box springs should also be covered with some type of encasement and sealed for at least 1 year as well.
Bed bugs are sensitive to temperature extremes; therefore,
steam cleaning may also be helpful with bed bug removal. However, steam
cleaning may not be as effective as vacuuming because the heat may not
reach well-hidden bed bugs. Bed linens, curtains, clothes, and other
washable materials should be washed in hot soapy water and dried for at
least 20 minutes in a hot dryer. This should kill most bed bugs and
their eggs.6 In order to avoid spreading the infestation, it
is generally not recommended to take washable items to a professional
dry cleaner.14 Items that are not easily washable may be
placed in a sealed plastic bag in the freezer for at least 4 days. Any
discarded materials that may have been infested with bed bugs should be
placed in sealed bags and labeled as infested with bed bugs.6
Chemical Eradication: Pesticides
available to the general public are not recommended for the removal of
bed bugs. A licensed pest control company should be consulted for
chemical removal. Pesticides that have been effective at removing bed
bugs include diatomaceous earth, eugenol, imiprothrin, permethrin,
pyrethrins, resmethrin, and tralomethrin. Pesticides should be applied
to cracks and crevices on the baseboard and other bed bug hiding places.
Only pesticides that are labeled for use on carpets or furniture should
be used in such places. Pesticide use should be limited on mattresses
and other furniture to minimize exposure to humans. Space treatments
such as “bug bombs” are generally not recommended for the elimination of
bed bugs because they may cause the bugs to scatter, making their
removal more difficult.6
There have been cases of human toxicities (e.g.,
neurologic or respiratory) associated with the use of insecticides to
treat bed bug infestations. Most reactions were low in severity, but
there was one fatality attributed to the overtreatment of bed bugs.15
To minimize the risk of toxicity it is important that insectides be
applied appropriately by a certified pest control professional.
Inhabitants should also be adequately notified of insecticide
application, and insecticide-treated bedding should be washed or
changed.15
Successful eradication of bed bugs is expensive and
time-consuming. Once bed bugs are removed, it is important to seal
cracks and crevices where bed bugs commonly hide to prevent
reinfestation. Rooms should be inspected thoroughly and should not be
inhabited again until all bed bugs have been eliminated.
Treatment
There is very little evidence-based information about the
treatment of bed bug bites. Therefore, bed bug bites are generally
treated symptomatically (TABLE 1). Pruritic lesions can be
treated with topical nonprescription and prescription antipruritic
agents. Topical antipruritic agents that may provide relief include
emollients, cooling agents (e.g., camphor, menthol), anesthetics (e.g.,
pramoxine), corticosteroids (e.g., triamcinolone), and antihistamines
(e.g., diphenhydramine). The use of topical antihistamines is generally
limited due to the potential for allergic contact dermatitis.16 Oral antihistamines such as diphenhydramine and oral corticosteroids have also been used to treat the bites.
A case series of 17 patients determined that topical corticosteroids reduced the duration of lesions and provided itch relief.17
The case series also determined that oral antihistamines helped relieve
itch but did not reduce the duration of the lesions. More severe
reactions have been treated using high-dose oral corticosteroids
(prednisone 40-60 mg). However, the case series reported poor response
to prednisone 40 to 60 mg daily.17
Patients should be advised not to scratch the bites.
Scratching the bites will lead to inflammation and excitation of C-nerve
fibers, which will result in more itching and scratching and
potentially a secondary skin infection.16 If a secondary skin
infection does occur, it can be treated with topical antibiotics such
as mupirocin. Systemic antibiotics may be necessary in more severe
cases.13 In the rare instance of an anaphylactic reaction,
treatment is similar to other types of insect-induced anaphylaxis using
agents such as intramuscular epinephrine, antihistamines, and
corticosteroids.13 Patients who experience severe reactions to the bites should consider keeping an epinephrine pen on hand.
Prevention
Due to the challenges of eradicating bed bugs, prevention
of infestations is critical. Tips for the prevention of bed bugs include
eliminating clutter, sealing cracks and crevices in rooms, and
inspecting mattresses, headboards, and linens routinely. Used furniture,
clothing, and other items should be inspected thoroughly before
bringing them into the house (avoid purchasing used mattresses). When
spending the night at a new location, examine the room for signs of bed
bugs such as fecal and blood spots on the bed or a sweet, musty smell.
Role of the Pharmacist
Due to the rapid resurgence of bed bug infestations, it is
likely that pharmacists will encounter patients with questions and
concerns about bed bugs. It is important for pharmacists to
appropriately educate their patients about bed bugs and offer strategies
for their identification, eradication, and prevention (TABLE 2
provides a list of resources). Patient counseling for itching due to bed
bug bites includes bathing in cool or lukewarm water rather than hot
water, using a humidifier, and using mild and low pH cleansers and
moisturizers.16 It is important for pharmacists to understand
and recommend appropriate symptomatic treatment and counseling for
cutaneous and systemic reactions to bed bug bites.
Conclusion
Bed bugs are small, elusive insects that can be very
difficult to detect and eliminate. A combination of physical and
chemical means is generally needed to eradicate bed bugs. Infestations
are becoming increasingly more common in the U.S. The clinical responses
to bed bug bites vary and are generally treated symptomatically.
Eradication of the bed bugs, thereby preventing future bites, is the
primary goal of therapy.
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