SCABIES
Definition
Scabies is a contagious skin disease caused by Sarcoptes scabiei var hominis, an acarid ectoparasite transmitted by close personal contact. Lesions of scabies acquired sexually usually occur on the genitalia, lower trunk and thighs.
Clinical features
Symptoms begin about 4 weeks after primary infestation. People who have previously been infected and sensitised may develop irritation in a few hours.
In males, genital lumps may be the only complaint. The lumps occur
mainly on the penis, especially on the glans and prepuce, and scrotum. They may or may not itch and are inflamed, reddish-brown, indurated nodules up to 12 mm across. Careful search may reveal scabctic lesions on more typical sites such as finger webs, wrists, elbows, axillae, knees, buttocks and toe webs.
Symptoms may be masked In people who shower or wash frequently, the clinical signs of scabies may be minimal and atypical and burrows may be difficult to find. The use of topical applications containing steroids may also mask the clinical features and make diagnosis difficult
Diagnosis and investigation
The distribution of the rash, multiple lesions and the presence of burrows and intense irritation particularly when in bed or warm should suggest the diagnosis.
The diagnosis is made by the demonstration of the mite or its eggs. The mite occupies the end of the burrow and can be removed with a needle or scalpel, mounted on a clean slide and demonstrated by low power microscopy. If no burrows or mites can be found, microscopy of skin scrapings from inflamed areas prepared with 10% potassium hydroxide may reveal parts of an acarus, eggs or faecal pellets.
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