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What is Scabies?
 Scabies
is a highly contagious, severely itchy skin disease caused by an
itch mite known as Sarcoptes scabei var hominis, belonging to the
arachnoid family and genus Acarus.
It has an ovoid body, the adult female is
about 0.4 X 0.3 mm and male is 0.2 X 0.15mm in size and can only be
visualized microscopically.
The life cycle of Scabies Mite
The scabies mite lives and dies in the
burrows. Copulation occurs in the burrow excavated by the female, and as is the
nature's rule, the male dies soon after copulation. The female lays 2-3
eggs daily, which are thatched in one week. The female mite lives around one
month.
What are the signs and symptoms of
Scabies?
Usually scabies is a disease seen among
overcrowded families living in narrow congested rooms. It can also be
contracted from pet animals, when it is known as animal scabies.
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The itching starts about 5-30 days after the mite
infestation.
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The itching is particularly severe during night.
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The diagnostic lesion in scabies is the
Burrow, it is a wavy, thread like greyish line, a few millimeters to a
centimeter in length. The open end is usually seen as a papule or vesicle
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In severe cases, nodules(deep seated swellings)
may be seen
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Secondary lesions due to itching are
excoriations, erosions and crusting of the skin
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As scabies itch mite gets transferred from person
to person very fast, there is a typical history of more than one family member
suffering from "itching during night'.
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Infestation can also spread through the clothes,
bed sheets, sofas etc that are used by the patient.
Which are the characteristic sites of
involvement of scabies in the body?
Finger webs, flexor aspect of wrist, inner area
of elbows, anterior fold of axilla, below the breasts, in and around umbilicus,
genitalia and thighs are the most favoured sites.
Scalp, face, neck, palms and soles etc are
involved in infants
Are there different types of scabies?
Yes. besides the classical scabies
described above, following are the variants of scabies:
Clean Man's Scabies: In those who bath
daily and keep themselves clean, the lesions are scarce and barely
visible. Itching is minimal.
Scabies incognito: If strong steroids are
mistakenly applied, the lesions are suppressed and change morphology.
Infant scabies: Palms and soles, head
neck, face and the whole body is involved in babies. There may be circular
scaly patches, vesicles and pustules present in abundance. Often misdiagnosed
and mistreated.
Norwegian scabies: Very severe crusted
scabies in the immune deficient and mentally retarded with lesions teeming with
hundreds of thousands of mites!
Animal scabies: If you have a cat or dog
which has scabies, your household, especially children can get animal scabies.
The lesions are seen only in areas which are in direct contact with the pet.
Burroughs are conspicuous in animal scabies by their absence.
Nodular Scabies: The mites burrow deeper
in certain areas, especially the male genitalia and inguinal folds, forming
brownish itchy deep seated nodules. These are resistant to normal modes of
treatment.
Sexually Transmitted Scabies: Scabies can
get transmitted following a sexual contact and can co exist with other STDs
like HIV, syphilis, gonorrhoea, chancroid,pubic louse etc.
Scabies bullosa: Vesicular and bullous
eruptions are seen in infants afflicted with scabies
Scabies ide and pompholyx: In severe
scabies, the skin develops an allergic response to the mite and its excretory
product which manifest as vesicular eruption along the sides of the fingers and
toes.
How is Scabies managed?
Treatment of scabies involves:
Patient Education:
All persons in the household, whether itching or
non itching should be treated.
Even after effective treatment the itching may
persist for upto two weeks
The clothes should be disinfected.
Woolen blankets etc should be kept locked
inside the cupboard, as the mites die off if they do not come in contact with
humans for 3-5 days
The applications should be repeated on weekly
base to prevent the eggs developing into adults.
Medical Therapy
Specific:
The Drug of Choice is Permethrin 5% cream or
lotion:
Apply full body, wash off after 8-10 hours
Usually single application enough, but in severe
cases, I advise a second application after one week
Can be used in infant above the age of 2 months.
Use in pregnancy controversial, so not advised.
Lindane(1% Gamma Benzene Hexa Chloride):
12 hours single application, repeat SOS after one
week
Avoided in children above 6 years, pregnancy and
patients with a history of seizures and neurological disorders
25% Benzyl Benzoate emulsion:
Should be kept on the body for 3 days
Repeat after 1 week
Over enthusiastic applications may cause irritant
dermatitis
Not advised in pregnancy and children below 3
years
May be diluted with half amount of water in
children 3-10 years
May have a stinging sensation
Sulfur: 6% precipitated sulfur in
petrolatum for 3 nightly applications. Can be used in infants even below
2 months and in pregnancy and lactation.
Crotamiton
Not very effective
An alternative in children and lactating
Nodular Scabies: Topical or
intra lesional steroids followed by the above therapy
Non Specific symptomatic treatment
Systemic antibiotics: If secondary
infection present
Antihistamines: To relieve itching
Systemic Therapy
Ivermectin is a new drug indicated in
treating severe types of scabies. Only to be used under medical supervision.
Conclusion: Scabies is a very common
disease, but still misdiagnosed and mistreated because of varied presentations.
If not treated properly, the course of scabies can run into months. No wonder
then, that in the pre, anti-scabicidal medication era, it was also known
as the Seven Year Itch!
Aside: Know any other Seven Year Itch?
Marital life is also known as the Seven Year Itch. Wonder Why?!:-)
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Dr.Hanish Babu, MD
