The Scabies Mite

Yvonne Hanson
Senior Infection Prevention Nurse
Aims and Objectives:
By the end of this session – you will definitely be
itching! And know:
• what the scabies mite looks like
• a little about their history
• what signs and symptoms to look for
• and understand the difference between ‘normal’
scabies and ‘crusted’ scabies
• how to apply treatment
• that you do not want to catch them – ever!
Sarcoptes scabiei (scabies)
It is a worldwide disease, more common where overcrowded conditions
However, It can affect any individual irrespective of social class, age or
The Scabies Mite (female)
Creamy white body
Suckers to keep it
Inside the burrow
Brown legs
Pretty? (magnified 50 times in order to see it)!
“Scabies” is derived from the Latin word
for “scratch” (scabere) and the Greek
sarx (flesh) and korptein (to smite or cut)
It is suspected that some biblical
“leprosy” (Hansen’s disease) was actually
Aristotle (384-323 BC) mentioned "lice in
the flesh" that produced vesicles
• Archeological evidence and Egyptian
hieroglyphics, suggests Scabies has been
irritating mankind for at least 2,500 years!
And Kirklees and Wakefield PCTs!
World wide there are an estimated 300
million cases a year
immunocomprimised people more
likely to develop Norwegian (crusted)
7% of people will develop nodular
scabies (nodules can last for several
Life Cycle of the Scabies Mite
Cycle normally takes just 12 days
Population of mites
• Numbers of adult mites
(burrows) build up slowly
• Symptoms only start after
several weeks
• The number of active
females increases until
– Immune response inhibits
– Scratching eliminates many
Adult female
• Adult female mites form
burrows in the stratum
corneum (dry horny layer of
• They cut into the cells using
sharp “elbow” joints on the
front pair of legs and
secrete a skin dissolving
• Usually only have 10 – 15
live mites on the body
• Obligate parasite (lives its
entire life on the host)
• Newly matured females form a short burrow
and wait for a male to find them
• Males and females mate in the burrow
• Males then wander off – in search of other
• They lay eggs, defecate (scybala), and die in
the burrow
• The female enlarges the burrow and stays
there for the rest of her life – burrows about
2-5mm per day (nodular scabies if she goes
too deep)?
• Larva makes its way to skin surface
• Female may live for 60 days
• Can lay 150 – 180 eggs
• Can ‘travel’ 10 – 15 cm under the skin
Site where she has burrowed
Mite, just under the skin
How is scabies transmitted/contracted?
• It cannot fly, but can crawl as fast as 2.5 cm per minute
• Juvenile mites run around on the skin surface
– Able to transfer
– Short-lived – 3 days per stage
– Can mature on new host – females and males
• Male mites run around on the skin surface
– Able to transfer
– Not able to reproduce
• Female mites in burrows
– Long lived – cannot leave burrow
– Not able to transfer
Factors affecting transmission
• Scabies is transmitted during prolonged skin to skin contact
(hand holding is the most common way)
– To allow the mite to cross over
– To allow enough mites to cross over
• It can be sexually transmitted
• ‘Normal’ scabies is not usually transferred via linen, but
‘crusted’ scabies can be
Signs and Symptoms
• Can be up to 6 – 8 weeks before first symptoms develop:
– Mild fever
– Irritability of skin, soon followed by severe itching (worse at
– Non-specific rash on
• Midriff
• Thighs
• Wrists and forearms
• Unfortunately, these signs are often overlooked, long term can
result in eczema and dry areas
• Infants often develop pustules on hands and feet
Hand and Wrist
Axilla (under arm)
Webbing (between fingers)
Front of hand – does it look like a skin problem
you have seen before?
Scabies or Eczema?
Diagnosis (Why is it known as the ‘seven year’ itch)?
Scabies is a great masquerader that mimics other
skin problems, e.g. impetigo, vasculitis, insect bites,
psoriasis, all of which complicate diagnosis
Clinical diagnosis
• Skin scrapings
• Clinical diagnosis (what do we
• Ink test
The most difficult job is treating
asymptomatic contacts – why?
Rules for treating
• Although mites may only burrow in certain places juveniles may be
found over the whole body
• Wearing gloves and a disposable apron, apply cream or lotion to
cool dry skin (not after a hot bath) to all skin surfaces from head to
toe (study):
 including under nail ends – is especially important for infants and
 awkward places such as the back, soles of the feet, between fingers
and toes, and the genitals.
 Pay special attention to the areas where mite burrows most commonly
occur, the front of the wrists and elbows, beneath the breasts, the
armpits, and around the nipples in women.
• Repeat treatment after 7 days
• If you wash your hands before end of treatment - reapply
Treatment options
• Malathion 0.5% liquid
– Used from 1980s
• Needs 2 applications
• Requires thorough
• Not irritant
• Unclear how effective
• Possible resistance
Treatment options
• Permethrin 5% cream
– Used since early 1990s
• Needs 2 applications
• Can cause tingling and/or
numbness (paraesthesia)
• Often need >1 tube
• Has the best clinical
evidence - >90% effective
Scabies in Care Homes
• The normal chain of contacts in care is
– Residents
• Resident relatives and friends
– Care staff
• Care staff families and friends
– Non-care staff and visiting workers
• Need to set up a hierarchy of risk
Treatment of Scabies Outbreak in a Nursing Home
Staff Member
No Treatment,
monitor over
the next 7 days
Monitor & retreat
if necessary using
a topical + Ivermectin
A 2nd Ivermectin dose +
topical may be needed in
cases of severe crusted
If signs &
symptoms are
evident begin
family member
Permethrin Permethrin
Permethrin Permethrin No Treatment No Treatment
but monitor
Monitor & retreat if
N.B. The itch of scabies continues for 2 weeks or more
following treatment. Relieve the itch with Eurax or
In severe cases of crusting using an emollient to help
remove crusts will enable treatment to work more
Ian F Burgess, Medical Entomology Centre, Insect Research & Development Limited
After treatment
• Itch can persist for up to 2 weeks – may
require separate therapy
• Nodular scabies – nodules can remain for
months (not infectious)
– Antihistamines, creams
Environmental Precautions
• Patients clothing should be placed into soluble bags
• Hoover bags should be discarded after each use into
a plastic bag and tied immediately
• Clothes, towels, and bed linen should be machine
washed at 50°C or above after the first application of
treatment. This kills the scabies mites.
• Keep any items of clothing that cannot be washed,
in plastic bags for at least 72 hours to contain the
mites until they die
• Pressing clothes with a warm iron, dry cleaning, or
putting items in a dryer on the hot cycle for 10–30
minutes is also effective
Crusted Scabies
Norwegian (Crusted Scabies) is:
• Highly contagious due to the large
number of parasites embedded in the
crusts possibly close to 1 million mites!
• Crusted scabies is more easily
transmitted through contact with
towels, bedding and upholstery
Toe of an immunocomprimised patient
Rules for treating crusted scabies
• Ensure thorough application of treatment
– Work well into crusts
– Ensure sub-ungual (under nail) areas well treated
– Include scalp if appropriate
– Pay particular attention to any dry skin on head, e.g.
around nose or behind ears
• May require extra applications of scabicide
• May require use of keratolytics (medications designed to
dissolve skin flakes and scales)
Points to Note:
Notify the Health Protection Unit (HPU) of outbreak (two or more residents
Do liaise with the local infection control team or HPU for support and advice
temporarily close to admissions / respite patients until completion of the first
treatment (post an outbreak notice on the door)
Follow the outbreak care pathway (downloadable from the IPC website)
All GPs should be informed of the problem
Staff who have had one treatment can return to work
If you have had scabies once, you can catch it again (symptoms will show
Persistent symptoms for more than 3 weeks may indicate that the treatment
has not been successful (risk assess as further treatment may be required
Secondary bacterial infections can develop as a result of scratching (may
require antibiotics)
It is really important to maintain vigilance – remember symptoms may not
show until up to 6 weeks after contracting the infection
Everyone who is treated should be treated on the same day
Scabies cannot be caught from pets or other animals
Are you itching to ask questions?

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