Scabies
(SKAY-bees)
Scabies has played an important role
in world history, with epidemics partially coinciding with military activities
and major social upheavals. Scabies has been recognized as a disease for
approximately 2500 years. Historically, it was treated with topical sulfur, a
treatment still in use today.
Like syphilis, scabies has come to be
known as the great imitator. Its spectrum of clinical manifestations may lead
the practitioner to the wrong diagnosis.
The phrase "7-year itch" was first
used with reference to persistent, undiagnosed infestations with scabies, not as
a movie title.
Pathophysiology:
The mite, S scabiei, spreads disease through direct and prolonged
contact with the host. The mite remains viable for 2-5 days on inanimate
objects; therefore, transmission through fomites, such as infected bedding or
clothing, is possible, but less likely. Once bound to their host, 10-15 mites
mate on the surface of the skin.
After mating, the male mite dies. The
female mite burrows into the epidermis of the host using her jaws and front
legs, where she lays up to 3 eggs per day for the duration of her 30- to 60-day
lifetime. An affected host harbors approximately 11 adult female mites during a
typical infestation. The eggs hatch in 3-4 days. The larvae leave the burrow to
mature on the skin. Fewer than 10% of the eggs laid result in mature mites.
A delayed type IV hypersensitivity
reaction to the mites, their eggs, or scybala (packets of feces) occurs
approximately 30 days after infestation. This reaction is responsible for the
intense pruritus, which is the hallmark of the disease. Individuals who are
already sensitized from a prior infestation can develop symptoms within hours.
Scabies is usually transmitted by
direct contact with an affected individual. Although disputed, some believe one
can become infested by indirect contact with the personal items or clothing of
an affected person because the mite can survive away from the skin for 2-5 days.
This is much more likely to occur in the environment of someone with crusted or
hyperkeratotic scabies.
In 1848, Norwegians Danielssen and
Boeck described a highly contagious variant of scabies that occurs in
immunocompromised patients. Crusted or hyperkeratotic scabies, as it has come to
be known, is an overwhelming scabies infestation. This rare form of scabies
occurs in elderly or mentally incompetent patients. Because of an impaired
antibody response, these individuals can be infested with thousands to a couple
million mites.
What is scabies?
Scabies is an infestation of the skin
with the microscopic mite Sarcoptes scabei. Infestation is common, found
worldwide, and affects people of all races and social classes. Scabies spreads
rapidly under crowded conditions where there is frequent skin-to-skin contact
between people, such as in hospitals, institutions, child-care facilities, and
nursing homes. However due to weakened immunity, elderly are more
susceptible to scabies.
The scabies mite
The mite is too small to be visible
by naked eye. The female mite penetrates into the skin by its forelegs and
mouth. It digs tunnels and lays down its eggs. The eggs hatch in 3 to 4 days.
The mites mature in about 10 days, and then start to breed the next generation.
What are the signs and symptoms of
scabies infestation?
Pimple-like irritations, burrows or
rash of the skin, especially the flexural areas of wrists, elbows, or knee; the
penis, breast, or shoulder blades, armpits, nipples, lower abdomen and external
genitalia. The face and scalp of elderly are usually spared.
Rash develops at the point where the
mite penetrates the skin. Thread like tunnel (usually less than 1 cm) can be
seen as they dig tunnels under the skin.
If the infected person is allergic to
the mite or its excreta, he or she may develop blisters.
The main symptom is intensive
itchiness in the infected areas, which is more severe at night and after hot
bath. Sores on the body caused by scratching. These sores can sometimes
become infected with bacteria.
How did I get scabies?
By direct, prolonged, skin-to-skin
contact with a person already infested with scabies. Contact must be prolonged
(a quick handshake or hug will usually not spread infestation). Infestation is
easily spread to sexual partners and household members. Infestation may also
occur by sharing clothing, towels, and bedding.
Who is at risk for severe
infestation?
People with weakened immune systems
and the elderly are at risk for a more severe form of scabies, called Norwegian
or crusted scabies.
How long will mites live?
Once away from the human body, mites
do not survive more than 48-72 hours. When living on a person, an adult female
mite can live up to a month.
Did my pet spread scabies to me?
No. Pets become infested with
a different kind of scabies mite. If your pet is infested with scabies, (also
called mange) and they have close contact with you, the mite can get under your
skin and cause itching and skin irritation. However, the mite dies in a couple
of days and does not reproduce. The mites may cause you to itch for several
days, but you do not need to be treated with special medication to kill the
mites. Until your pet is successfully treated, mites can continue to burrow into
your skin and cause you to have symptoms.
How soon after infestation will
symptoms begin?
For a person who has never been
infested with scabies, symptoms may take 4-6 weeks to begin. For a person who
has had scabies, symptoms appear within several days. You do not become immune
to an infestation.
When should I think about scabies?
-
Unexplained pruritus especially if
other contacts are also itchy
-
`Atopic or irritant dermatitis' of
very recent onset
-
Persistent insect bite reactions
-
Recurrent impetigo with itch
-
Pustular lesions on the palms and
soles particularly in the young
-
Unusual urticaria
-
Unusual pruritic psoriasiform
rashes that are crusted and scaling or blistering
How is scabies infestation
diagnosed?
Diagnosis is most commonly made by
looking at the burrows or rash. A skin scraping may be taken to look for mites,
eggs, or mite fecal matter to confirm the diagnosis. If a skin scraping or
biopsy is taken and returns negative, it is possible that you may still be
infested.
Typically, there are fewer than 10
mites on the entire body of an infested person; this makes it easy for an
infestation to be missed.
Diagnosis:
Who should be treated for scabies?
Anyone who is diagnosed with scabies,
as well as his or her sexual partners and persons who have close, prolonged
contact to the infested person should also be treated. If your health care
provider has instructed family members to be treated, everyone should receive
treatment at the same time to prevent reinfestation.
Can scabies be treated?
Yes. Several lotions are
available to treat scabies. Always follow the directions provided by your
physician or the directions on the package insert. Apply lotion to a clean body
from the neck down to the toes and left overnight (8 hours).
After 8 hours, take a bath or shower
to wash off the lotion. Put on clean clothes. All clothes, bedding, and towels
used by the infested person 2 days before treatment should be washed in hot
water; dry in a hot dryer.
A second treatment of the body with
the same lotion may be necessary 7-10 days later.
Pregnant women and children are often
treated with milder scabies medications.
General strategies in scabies
management
An inviolable principle of scabies
treatment is to treat all significant contacts. In practice this means all
contact should have at least one treatment. Patients with definite or probable
scabies should have two treatments. Caution should be exercised in treating
infants, pregnant or lactating women, and the very elderly, as some preparations
may be more toxic.
The treatment choice rests largely
between topical permethrin or lindane applied to the skin. Permethrin is
preferred because of its apparent lesser toxicity. A large number of other
agents may be used in special circumstances. The application must be done
scrupulously. If one burrow is spared then the infestation will persist. The
cream therefore needs to be massaged under nails and reapplied to any areas that
are washed
Antiscabetic treatment
|
Treatment |
Comment |
|
Permethrin |
A
synthetic pyrethroid which is probably the safest antiscabetic treatment.
Proven effectiveness. Probably safe in infants, pregnant and lactating
women, and the elderly. |
|
Benzyl
benzoate |
This is
often irritating. Toxicity is uncertain. It can be used as a spray for
furnishings and the environment where there is heavy contamination.
|
|
Lindane(gamma benzene hexachloride) |
The
potential for neurotoxicity limits the use of this agent particularly in
infants, pregnant and lactating women, and in the elderly. |
|
Ivermectin |
Single
dose may be effective. Simultaneous topical treatment is optional.
Sometimes repeated doses are necessary. This drug is an important
development in treating compromised patients, crusted Norwegian scabies,
widespread unresponsive scabies and possibly some community epidemics in
nursing home situations. Before prescribing, medical practitioners should
be aware of the potential adverse effects and controversies in treating
the young or the very elderly on multiple medications. |
|
Miscellaneous other agents
including maldison, and 6% precipitated sulphur cream |
These
agents require specialised experience and are not recommended as first
line treatment. Some of these may also be used for spraying furniture
|
Management
of residents and staff for old age home
Staff should closely monitor the
conditions of themselves and their residents. Immediate medical advice should be
sought when a person have symptoms suggestive of scabies infection.
During a scabies outbreak, people who
are in close contact with the patient, eg. roommates and staff, should apply the
anti-scabies medication to prevent the spread of the disease.
Staff should wear gloves and apron
when doing cleansing and taking care of the infected patient.
How soon after treatment will I
feel better?
Itching may continue for 2-3 weeks,
and does not mean that you are still infested. Your health care provider my
prescribe additional medication to relieve itching if it is severe. No new
burrows or rashes should appear 24-48 hours after effective treatment.
Mortality/Morbidity
Scabies is unlikely to cause a
long-term disease state in healthy individuals. However, without adequate
treatment, the lesions and associated pruritus may last for weeks to months.
Immunocompromised individuals are
likely to develop crusted scabies, which may be impossible to fully eradicate.
Those infested may contract secondary
bacterial infections via skin abrasion due to excessive scratching. These
secondary infections may result in cellulitis, lymphangitis, and acute
glomerulonephritis. Other than deaths related to secondary infection, scabies
causes no appreciable mortality.
The above opinionated
views and information serves to educated and informed consumer . The information
provided herein should not be used during any medical emergency or for the
diagnosis or treatment of any medical condition. It should not replaced
professional advise and consultation. A licensed physician should be consulted
for diagnosis and treatment of any and all medical conditions
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