SUPPLEMENT KNOWLEDGE WOUND CARE

KNOWLEDGE WOUND CARE SUPPLEMENT
Causes and effective management
of insect bites in the UK
Insects play an important role in maintaining the
world’s ecosystem (Zhu and Stiller, 2002) but many
of them feed on other animals. Humans are relatively
hairless and provide an easy target, especially when
partly clothed (Cohn, 2003). Biting insects common
to the UK include midges, gnats, mosquitoes, flies,
fleas, lice, mites, ticks, and bedbugs (Fig 1).
Although their bites rarely cause serious problems, the
salivary gland excretions they deposit contain various
antigenic substances that may provoke a reaction in
susceptible people (Prodigy, 2003).
Insect habits and habitats
Bedbugs These are nocturnal blood-sucking parasites
that feed at night. During the day they hide in
mattresses and bed covers, and in cracks in walls,
floors and furniture, where they can survive for more
than a year without a suitable food source (Fletcher et
al, 2002; Zhu and Stiller, 2002). Bedbug bites do not
usually cause reactions.
Fleas These live on small rodents, bats, birds and pets,
and move from them to feed on humans. Most flea bites
are not associated with disease transmission though rat
fleas can transmit plague (Zhu and Stiller, 2002).
Body lice These live on clothing and move to nearby
body areas to feed. Pubic or crab lice live in the pubic
or perianal areas – both are blood-feeding parasites.
Body lice bites can cause allergic hypersensitivity,
erythematous papules (small elevated palpable lesions),
pruritus (itching), swelling, excoriation,
lymphadenopathy and conjunctivitis. Crab lice rarely
cause these conditions (Zhu and Stiller, 2002).
Mosquitoes There are many species of mosquito. The
females need a blood meal to produce eggs but males
feed on plant nectar. Skin reactions are common at the
site of bites and, worldwide, mosquitoes transmit
diseases from one bitten host to the next. These include
malaria, yellow fever, dengue fever (acute arbovirus
infection), lymphatic filariasis (caused by the lymphatic
filarial parasites), and encephalitis (Zhu and Stiller, 2002).
West Nile virus is the most likely mosquito-borne
disease in the UK. It is uncommon because the
population density of mosquitoes is relatively low
(Prodigy, 2003). In most people the infection is
asymptomatic or causes a mild influenza-like illness. It
may cause encephalitis or aseptic meningitis, especially
in people aged over 50 (Prodigy, 2003; Crook et al, 2002).
RGN, RNT, DipN, is senior lecturer
and programme leader, emergency
nursing, University of Hertfordshire
Marion Richardson describes
the causes of insect bites
and the management of this
uncomfortable problem
KEY WORDS
Insects
Bites
Inflammation
Midges Only female midges attack, often in swarms at
sunrise or sunset and with a higher frequency in
seasons with increased humidity (Cohn, 2003). Midges
are rarely vectors of disease.
Scabies These mites are found either on animals or in
stored goods. They mate on the skin and the female
burrows into the epidermis, usually on the hands, wrists
or elbows, leaving a small opening and a linear burrow.
Scabies causes severe itching, especially at night, not
only at the burrowing sites but also over much of the
body. Secondary bacterial infection is a complication
(Zhu and Stiller, 2002).
Ticks These are blood-sucking parasites that may
embed in the human skin (Storer et al, 2003). They are
found in woodland areas with plentiful wildlife (Cutler,
1997) and are especially prevalent in spring and early
summer. Ticks often attach in obscure areas such as
behind the ear (Storer et al, 2003) and once attached,
may feed for many weeks in preparation for egg-laying
(Howell, 2001).
Tick bites often cause local allergic reactions such as
eczematous changes, urticaria, blistering, and temporary
alopecia (hair loss). Susceptible people may have a
delayed hypersensitivity reaction including symptoms of
BOX 1. BITES AND SUGGESTED CAUSES (ADAPTED FROM PRODIGY GUIDELINES, 2003)
LOCATION
SUGGESTED CAUSE
Abdomen and thighs – from animal sitting on lap
Cheyletiella mite
Below knees and most profuse around ankles. Clusters of a bite found elsewhere on the body if the person has been
lying
on an infested rug or sofa
Cat or dog fleas
Scattered all over the body
Bird fleas, bird mites or bedbugs (Burns, 1998)
Patterned areas around the elastic of clothing
Lice or fleas
Primarily on exposed areas
Mosquito and fly bites
NT 1 June 2004 Vol 100 No 22 www.nursingtimes.net
Marion Richardson, BD, CertEd,
REFERENCES
ATTRACT (2003) Question: I have
a patient with possible tick bites.
Wales: NHS Wales. www.attract.
wales.nhs.uk
Burns, D.A. (1998) Diseases
caused by arthropods and other
noxious animals. In: Champion,
R.H. et al (eds) Textbook of
Dermatology. Oxford: Blackwell
Science.
Cohn, B.A. (2003) Biting midges –
those marauding ‘no-see-ums’.
International Journal of
Dermatology; 42: 6, 459–460.
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KNOWLEDGE WOUND CARE SUPPLEMENT
FIG 1. DIFFERENT TYPES OF BITING INSECTS THAT ARE COMMON IN THE UK
Coloured scanning electron
micrograph of a cat flea’s head
Macrophotograph of
bedbugs on human skin
Coloured scanning electron micrograph of pubic lice,
also known as crab lice, hanging from human hair
SPL
Coloured scanning electron
micrograph of a mosquito
fever, pruritus, and urticaria (Storer et al, 2003).
Lyme disease is transmitted by one species of tick
(Ixodes ricinus) and, though uncommon in the UK, its
incidence is rising – currently there are approximately
200 cases a year (Prodigy, 2003; McGarry et al, 2001).
Lyme disease that is caused by a spirochaete can
result in arthritis, meningitis, neuropathies, carditis,
and encephalopathy.
occur if there are numerous bites or the local reaction is
severe (Prodigy, 2003). Anaphylactic reactions to insect
bites are uncommon. Typical reactions are listed in Box
2.
Bite reactions can persist for months – for example,
tick bites may result in persistent nodules or papules
caused by retained mouthparts. However, most tick bites
heal within three weeks (Wilson and King, 2003).
Distribution and appearance of bites Typical
distribution of insect bites and their possible causes are
listed in Box 1. Reactions to bites are varied. The first
time a person is bitten there is usually no reaction
unless the saliva contains a substance that is likely to
cause direct injury, for example, parasites and bacteria.
After repeated bites, sensitivity occurs (Prodigy, 2003);
an itchy papule develops about 24 hours after each bite
and lasts for several days.
After further bites, an extremely itchy rash develops
immediately and is followed by a firm, pruritic papule.
Following continued and repeated exposure, no reaction
occurs (Prodigy, 2003).
Management of bites Prodigy (2003) notes that
there is a lack of good quality evidence regarding the
management of insect bites.
Symptoms Burns (1998) notes that irritation is an
almost constant symptom. Rubbing and scratching may
increase the inflammatory changes.
Papular urticaria is common in young children and
those with a history of atopic dermatitis. It is caused by
a sensitivity to the bites and consists of groups or lines
of very itchy, indurated papules that persist for up to two
weeks (Prodigy, 2003; Stibich et al, 2001).
Bullous reactions (fluid-filled blisters larger than 5mm
in diameter) are common in the lower legs and may
occur at other sites, especially in children (Burns, 1998).
Chronic cases in adults can appear as lichen simplex
– rough thickened epidermis (Prodigy, 2003).
Bacterial infection may be introduced at the time of
the bite or may occur as a result of scratching.
Systemic urticarial reactions occur in some people
several hours after the bite, and fever and malaise can
NT 1 June 2004 Vol 100 No 22 www.nursingtimes.net
Midges, gnats, mosquitoes, flies, and ticks Bites
from these are generally ‘one-off’ incidents and
treatment of symptoms is usually sufficient. Creams or
lotions with soothing qualities are prescribed and may
relieve itching.
Antihistamines are of little help in treating pruritus but
a short course of sedative oral antihistamine at night
may allow sleep and break the itch-scratch cycle
(Prodigy, 2003). If local inflammation is present, a
topical corticosteroid may help to relieve itching.
For urticarial reactions, a short course of oral
antihistamine may be appropriate to help control
itching, the appearance of wheals, and sleeplessness
(Drug and Therapeutics Bulletin, 2002). People who
suffer severe anaphylactic reactions to these insect bites
need to carry adrenaline (Stringer et al, 2002).
Ticks must be removed as soon as possible after the
bite to minimise complications. The literature has many
suggestions as to how tick removal is best performed to
achieve the optimum outcome.
The Prodigy guidelines (2003) suggest using finepoint tweezers to grasp the tick as close to the skin as
possible and then pulling gently. It is important to avoid
squeezing the body of the tick. The site of the bite
should be cleaned with disinfectant.
Routine use of antimicrobial prophylaxis or serological
tests for Lyme disease following a tick bite is not
REFERENCES
Crook, P.D. et al (2002) West Nile
virus and the threat to the UK.
Communicable Disease and Public
Health; 5: 2, 138–143.
Cutler, C. (1997) Lyme borreliosis:
an update. Practice Nursing; 8: 8,
33–35.
Driver, C. (1999) Happy holiday?
Primary Health Care; 9: 5, 14–19.
Drug and Therapeutics Bulletin
(2002) Oral antihistamines for
allergic disorders. Drug and
Therapeutics Bulletin; 40: 8, 59–62.
Fletcher, C.L. et al (2002)
Widespread bullous eruptions due
to multiple bed bug bites. Clinical
and Experimental Dermatology;
27: 1, 74.
Fradin, M.S., Day, J.F. (2002)
Comparative efficacy of insect
repellents against mosquito bites.
New England Journal of Medicine;
347: 1, 13–18.
Howell, K. (2001) Tick-borne
encephalitis. Practice Nursing; 12:
6, 240–243.
McGarry, J.W. et al (2001)
Arthropod dermatoses acquired in
the UK and overseas. The Lancet;
357: 9274, 2105–2106.
Prodigy (2003) Prodigy Guidance
– Insect Bites and Stings. London:
Prodigy.
www.prodigy.nhs.uk/guidance.
asp?gt=Insect%20bites%20and
%20stings
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KNOWLEDGE WOUND CARE SUPPLEMENT
BOX 2. TYPICAL REACTIONS TO BITES (ADAPTED FROM PRODIGY GUIDELINES, 2003)
BITING INSECT
PRESENTATION
Midges, mosquitoes, gnats
Usually small papules
Wheals (elevated area of cutaneous oedema) and bullae in sensitised individuals
Fleas – animal/human
Bites may be grouped in lines or irregular clusters
Usually cause papular urticaria in sensitised individuals
Occasionally bullae
Horseflies
Often very painful with cutaneous wheal which may be accompanied by urticaria, dizziness, weakness, wheezing, or angio-oedema. Secondary infection is common
Bedbugs
Painless bites. May be no reaction if the individual has not been previously bitten. Sensitised people – very irritating wheals or papules surmounted by haemorrhagic puncta (very small bleeding points)
The Blandford fly (found in an arc running from into Dorset
Bites usually on the legs and are very painful. Various reactions range from small blister to large haemorrhagic indurated lesion. May be accompanied by fever or joint pains
East Anglia through Oxfordshire Cheyletiella mites (often
harboured by dogs or cats)
Intensely itchy papules where mites have fed on skin. May be a tiny vesicle surmounting the papule. Older lesions may show necrosis
REFERENCES
Stibich, A.S. et al (2001) Insect
bite reactions: an update.
Dermatology; 202: 3, 193–197.
Storer, E. et al (2003) Ticks in
Australia. Australasian Journal of
Dermatology; 44: 2, 83–89.
Stringer, C. et al (2002)
International travel and health
assessment. Nursing Standard;
16: 39, 49–54.
Wilson, D.C., King, J.L.E. (2003)
Arthropod bites and stings. In:
Freedberg, I.M. et al (eds)
Fitzpatrick’s Dermatology in
General Medicine. London:
McGraw-Hill.
Zhu, Y.I., Stiller, M.J. (2002)
Arthropods and skin diseases.
International Journal of
Dermatology; 41: 9, 533–549.
Mites in stored products such as Intensely itchy, minute, pruritic papules or papulovesicles (2–3mm red, excoriated,
crusted grain, flour, and cheese papules in linear groupings) on exposed parts of the body
recommended but people who develop a skin lesion at
the site of the bite or pyrexia within one month of
removing a tick should be advised to seek medical
advice promptly (ATTRACT, 2003).
Fleas, mites, bedbugs, and lice Bites from these
require symptomatic treatment but it is more important
to find the source of the infestation and eliminate it.
Cat and dog fleas should be managed with an
appropriate insecticide. It should be used to treat the
animal, its bedding, carpets, and soft furnishings
(Prodigy, 2003). Regular, thorough vacuuming should
be undertaken.
In the case of bedbugs, insecticide should be applied
to walls and furniture that is likely to be harbouring the
bug. Soft furnishings and bedding should be washed.
Mite infestation should be eradicated and clothes
regularly laundered (Zhu and Stiller, 2002).
Preventing bites There is a consensus in the
literature that the most effective insect repellents are those
containing DEET (diethyltoluamide) and the stronger the
solution of DEET, the longer the effectiveness of the
repellent (Cohn, 2003; Prodigy, 2003; Fradin and Day,
2002). DEET is remarkably safe – very few cases of
serious toxic effects have been reported.
However, DEET is a plasticiser capable of dissolving
watch crystals, spectacle frames, and certain synthetic
fabrics (Fradin and Day, 2002). Stringer et al (2002)
advise that DEET should be avoided by pregnant
women and children.
While repellents not containing DEET do not provide
NT 1 June 2004 Vol 100 No 22 www.nursingtimes.net
such effective protection, they may be more acceptable
for some people in the UK, where mosquito-borne
diseases are not a substantial threat.
There is no evidence that ingested compounds such
as garlic and thiamine (vitamin B1) can help to repel
biting insects. However, oil-of-eucalyptus appears to
confer longer-lasting protection than other plant-based
repellents available (Cohn, 2003; Fradin and Day, 2002).
It is vital to reapply repellents regularly, particularly when
it is hot and humid (Stringer et al, 2002). Driver (1999)
says repellent is needed at sunrise and sunset to prevent
mosquito bites but at other times for other insects.
Clothing can be impregnated, especially at the wrist
and ankle bands – plug-in vaporisers or mosquito coils
can be used. Mosquito nets and other precautions are
not usually necessary in the UK.
Wearing appropriate clothing (long sleeves and long
trousers tucked into socks) will also help prevent
insect bites outdoors, though some insects can bite
through clothing. Clothes can be sprayed with DEET
for added protection.
Insect repellents against ticks are only useful for a few
hours (Howell, 2001) and it is best to avoid tick-infested
areas. Ticks are more visible on light clothing (Storer et
al, 2003), which should be checked regularly so they
can be removed as soon as possible (Cutler, 1997).
Conclusion The old adage ‘prevention is better than
cure’ certainly holds true where insect bites are
concerned. For most people bitten in the UK, the
reaction will be an irritating nuisance. However, an
unfortunate few will experience severe reactions and
may develop serious disease. ■
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