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| SCABIES MITES |
MITES
Mites,
along with ticks, are small arthropods belonging to the subclass Acari (also
known as Acarina) and the class Arachnida. The scientific discipline devoted to
the study of ticks and mites is called acarology. In soil ecosystems, mites are
favored by high organic matter content and by moist conditions, wherein they
actively engage in the fragmentation and mixing of organic matter.
Types of Mites
The
majority of mite species are harmless to humans, but a few species of mites can
colonize humans directly, act as vectors for disease transmission, or cause or
contribute to allergenic diseases.
v Mites which colonize human skin are the cause of
several types of skin itchy rashes, such as grain itch, grocer's itch, and
scabies. Sarcoptes scabiei is a
parasitic mite responsible for scabies
which is one of the three most common skin disorders in children.
v Demodex mites, which are common cause of mange in dogs and other
domesticated animals, have also been implicated in the human skin disease
rosacea, although the mechanism by which demodex contributes to the disease is
unclear.
v Chiggers are known primarily for their itchy bite, but they
can also spread disease in some limited circumstances, such as scrub typhus.
The house-mouse mite is the only
known vector of the disease rickettsialpox.
v Dust mites cause several forms of allergic diseases, including
hay fever, asthma and eczema, and are known to aggravate atopic dermatitis.
v House dust mites are usually found in warm and humid locations,
including beds. It is thought that inhalation of mites during sleep exposes the
human body to some antigens that eventually induce hypersensitivity reaction.
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SCABIES
i)What is scabies?
Scabies
is an infestation of the skin caused by the scabies mite Sarcoptes scabiei (see
image). The mite is very tiny, 0.2 mm to 0.4 mm long, and cannot easily be seen
without magnification. It occurs worldwide and in all races and social classes.
Scabies is not an indication of poor hygiene.
ii)How scabies is spread?
Scabies
is usually transmitted by direct skin-to-skin contact, or rarely, by underwear
or bed clothes that have been freshly contaminated by an infested person. The
mites can survive for only a few days off the human or animal body.
iii)Signs and symptoms
Scabies
and other mites usually infest the skin especially where there are creases,
such as:
v between the fingers
v on the front of the wrists
v in the folds of the elbows, armpits and buttocks
v genitals.
When
mites have been transmitted from animals (such as dogs) to people, the mites
are commonly found on areas of skin having contact with the animal, including
forearms, chest and neck. However, mites from animals cannot breed on humans,
so do not cause ongoing infestation. Scabies mites cause intense itching,
especially at night. Thread-like ‘tunnels’, about 10 mm long, may be visible as
grey lines in the skin, but they are often difficult to detect. Scabies
infection may appear on the genitals as small itchy lumps.
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iv)Incubation period
(time
between becoming infected and developing symptoms)
Itching
begins 2 to 6 weeks after infestation in individuals not previously exposed to
scabies and within 1 to 5 days in individuals previously exposed.
v)Infectious period
(time
during which an infested person can transmit the infestation to others)
Until
the mites and eggs are destroyed by treatment. People can be infectious even
before the itching begins.
vi)Treatment
Skin
disease caused by mites can easily be confused with other skin diseases.
Treatment should not be undertaken until the diagnosis has been confirmed by a
doctor, following examination of skin scrapings for mites. This is particularly
important for babies, pregnant women or people who already have other forms of
skin disease. Babies under 12 months of age need special treatment. Treatment
involves application of insecticidal cream, lotion or solution as prescribed by
a doctor. For see the Direction for the application of a topical scabicide (PDF
59KB) (opens in a new window) for detailed information on what you should do
and how to apply topical scabicides.
vii)Prevention
v Exclude people with scabies from childcare,
preschool, school and work until one day after treatment commences.
v All close (skin-to-skin) contacts and other people
in the same household should be treated at the same time, even if no itching or
other symptoms are present. By the time scabies is diagnosed in one person,
many other people may have been infested. If everyone is not treated at the
same time, treatment is likely to be unsuccessful.
v Underwear, clothing, towels, bed linen and personal
effects such as slippers, bed jackets, dressing gowns and knee rugs used by the
affected person in the 72 hours prior to treatment should be laundered using a
hot wash cycle (hotter than 50°C) or hot tumble dried to kill the mites. If
items are unable to be laundered or hot tumble dried, place them in a sealed
plastic bag and leave them for 72 hours before airing and reusing.
v Mattresses and upholstered furniture can be vacuumed
or gently ironed
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References
:
ii) http://en.wikipedia.org/wiki/Mite
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