Other skin disease that is
grouped into a sexually transmitted disease (STD) is Scabies. This time the learning
series about STD (
get to know STD) will discuss about Scabies. All the material
below is quoted from
Wikipedia entirely. Happy reading!
Scabies is an ancient disease.
Archeological evidence from Egypt and the Middle East suggests scabies was
present as early as 494 BC. The first recorded reference to scabies is
believed to be from the Bible (Leviticus, the third book of Moses) circa
1200 BC. Later, in the fourth century BC, the ancient Greek philosopher Aristotle
reported on "lice" that "escape from little pimples if they are
pricked" scholars believe this was actually a reference to scabies.
Nevertheless, Greek physician Celsus
is credited with naming the disease "scabies" and describing its
characteristic features. The parasitic etiology of scabies was later documented
by the Italian physician Giovanni Cosimo Bonomo (1663–99 AD) in his famous
1687 letter, "Observations concerning the fleshworms of the human
body". With this discovery, scabies became one of the first diseases with
a known cause.
Scabies (from Latin: scabere,
"to scratch"), also called Norwegian scabies or colloquially the seven-year
itch, is a contagious skin infection caused by the mite Sarcoptes scabiei. The mite is a tiny and usually not directly
visible parasite which burrows under the host's skin, causing intense allergic
itching. The infection in animals other than humans is caused by a different
but related mite species, and is called sarcoptic mange.
Scabies is classified by the World
Health Organization as a water-related disease. The disease may be transmitted
from objects, but is most often transmitted by direct skin-to-skin contact,
with a higher risk with prolonged contact. Initial infections require four to
six weeks to become symptomatic. Reinfection, however, may manifest symptoms
within as few as 24 hours. Because the symptoms are allergic, their delay in
onset is often mirrored by a significant delay in relief after the parasites
have been eradicated. Crusted scabies, formerly known as Norwegian scabies, is
a more severe form of the infection often associated with immunosuppression.
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| Norwegian Scabies in HIV patient, need 6 months from first itch to be like this (Source: Wikipedia) |
The characteristic symptoms of a
scabies infection include intense itching and superficial burrows. The burrow
tracks are often linear, to the point that a neat "line" of four or
more closely placed and equally developed mosquito-like "bites" is
almost diagnostic of the disease. In the classic scenario, the itch is made
worse by warmth, and is usually experienced as being worse at night, possibly
because there are fewer distractions. As a symptom, it is less common in the
elderly.
The superficial burrows of
scabies usually occur in the area of the hands, feet, wrists, elbows, back,
buttocks, and external genitals. Except in infants and the immunosuppressed,
infection generally does not occur in the skin of the face or scalp. The
burrows are created by excavation of the adult mite in the epidermis.
In most people, the trails of the
burrowing mites are linear or s-shaped tracks in the skin often accompanied by
rows of small, pimple-like mosquito or insect bites. These signs are often
found in crevices of the body, such as on the webs of fingers and toes, around
the genital area, and under the breasts of women.
Symptoms typically appear two to
six weeks after infestation for individuals never before exposed to scabies.
For those having been previously exposed, the symptoms can appear within several
days after infestation. However, it is not unknown for symptoms to appear after
several months or years. Acropustulosis, or blisters and pustules on the palms
and soles of the feet, are characteristic symptoms of scabies in infants.
The elderly and people with an impaired
immune system, such as HIV, cancer, or those on immunosuppressive medications,
are susceptible to crusted scabies (formerly called Norwegian scabies). On
those with weaker immune systems, the host becomes a more fertile breeding
ground for the mites, which spread over the host's body, except the face.
Sufferers of crusted scabies exhibit scaly rashes, slight itching, and thick
crusts of skin that contain thousands of mites. Such areas make eradication of
mites particularly difficult, as the crusts protect the mites from topical
miticides, necessitating prolonged treatment of these areas.
The symptoms are caused by an allergic
reaction of the host's body to mite proteins, though exactly which proteins remains
a topic of study. The mite proteins are also present from the gut, in mite
feces, which are deposited under the skin. The allergic reaction is both of the
delayed (cell-mediated) and immediate (antibody-mediated) type, and involves
IgE (antibodies, it is presumed, mediate the very rapid symptoms on
reinfection). The allergy-type symptoms (itching) continue for some days, and
even several weeks, after all mites are killed. New lesions may appear for a
few days after mites are eradicated. Nodular lesions from scabies may continue
to be symptomatic for weeks after the mites have been killed.
Scabies may be diagnosed
clinically in geographical areas where it is common when diffuse itching
presents along with either lesions in two typical spots or there is itchiness
of another household member. The classical sign of scabies is the burrows made
by the mites within the skin. To detect the burrow, the suspected area is
rubbed with ink from a fountain pen or a topical tetracycline solution, which
glows under a special light. The skin is then wiped with an alcohol pad. If the
person is infected with scabies, the characteristic zigzag or S pattern of the
burrow will appear across the skin; however, interpreting this test may be
difficult, as the burrows are scarce and may be obscured by scratch marks. A
definitive diagnosis is made by finding either the scabies mites or their eggs
and fecal pellets. Searches for these signs involve either scraping a suspected
area, mounting the sample in potassium hydroxide and examining it under a
microscope, or using dermoscopy to examine the skin directly.
Symptoms of early scabies
infestation mirror other skin diseases, including dermatitis, syphilis, various
urticaria-related syndromes, allergic reactions, and other ectoparasites such
as lice and fleas.
Mass treatment programs that use
topical permethrin or oral ivermectin have been effective in reducing the prevalence
of scabies in a number of populations. No vaccine is available for scabies. The
simultaneous treatment of all close contacts is recommended, even if they show
no symptoms of infection (asymptomatic), to reduce rates of recurrence. Asymptomatic
infection is relatively common. Since mites can only survive for two to three
days without a host, objects in the environment pose little risk of
transmission except in the case of crusted scabies, thus cleaning is of little
importance. Rooms used by those with crusted scabies require thorough cleaning.
A number of medications are
effective in treating scabies; however, treatment must often involve the entire
household or community to prevent reinfection. Options to improve itchiness
include antihistamines.
Permethrin
Permethrin is the most effective
treatment for scabies, and is the treatment of choice. It is applied from the
neck down, usually before bedtime, and left on for about eight to 14 hours,
then showered off in the morning. One application is normally sufficient for
mild infections. For moderate to severe cases, another dose is applied seven to
14 days later. Permethrin causes slight irritation of the skin, but the
sensation is tolerable. The medication, however, is the most costly of topical
treatments.
Ivermectin
Ivermectin is an oral medication
shown by many clinical studies to be effective in eradicating scabies, often in
a single dose. It is the treatment of choice for crusted scabies, and is often
used in combination with a topical agent. It has not been tested on infants and
is not recommended for children under six years of age.
Topical ivermectin preparations
have been found to be effective for scabies in adults, and are attractive due
to their low cost, ease of preparation, and low toxicity. It has also been
useful for sarcoptic mange (the veterinary analog of human scabies).
Scabies is one of the three most
common skin disorders in children, along with tinea and pyoderma. As of 2010 it
affects approximately 100 million people (1.5% of the population) and is
equally common in both genders. The mites are distributed around the world and
equally infect all ages, races, and socioeconomic classes in different
climates. Scabies is more often seen in crowded areas with unhygienic living
conditions. Globally as of 2009, an estimated 300 million cases of scabies
occur each year, although various parties claim the figure is either over- or
underestimated. About 1–10% of the global population is estimated to be
infected with scabies, but in certain populations, the infection rate may be as
high as 50–80%.
