Page 41 - LECTURE NOTES
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Historically
It has been recognized as a disease for over 2500 years. In 1687 Francesco Redi
identified Sarcoptes scabei Scabies is one of the first diseases with a known cause.
In Latin, scabere means to scratch. Romans used the term to describe any pruritic skin
disease; so, it has been known as the great imitator
Etiologic agent
Sarcoptes scabei var. hominis, the female measures 0.4mm long and 0.3mm broad
and the smaller male is 0.2mm long and 0.15 mm broad.
Epidemiology
9 Commoner in children and adolescents
9 It is a disease of disadvantaged community
9 Epidemic occurs during wars and social upheavals
9 Endemic in many developing countries
Transmission Pathogenesis
Female and male make mating on the surface of the skin. The male mite dies and the
gravid female mite burrows into the epidermis lays up to 3 eggs per day for the
duration of her 30-60 day lifetime.
In a typical infestation host harbors 8-11 adult female mites. The eggs hatch in 3-4
days and the larvae leave the burrow to mature on the skin.
Fewer than 10% of the eggs laid result in mature mites.
Type IV hypersensitivity reaction to the mites, their eggs, or scybala (packets of
feces) occurs approximately 30 days after infestation
Clinical features
Classic scabies:
The lesions are erythematous, excoriated, papulovesicular and found bilaterally. It
starts on the wrist, finger webs and on the medial sides of fingers, the flexor aspect of
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