Scabies is the most common mite infestation in human beings.

Scabies Causative Organism

The itch mite is Sarcoptes scabiei var hominis. It has an oval shaped body with four pairs of short legs. The female mite is larger than the male. In a usual patient of scabies, average number of mites is 10 to 12. However, in crusted scabies, it can be up to two million.

Mode of Transmission

Transmission is facilitated by overcrowding and poor hygiene. It also spreads by close physical contact including sex. As the mite does not survive for more than two days away from a moist environment, transmission through clothing is unlikely.

Clinical Features of Scabies

Extreme itching, which is more at night is usually considered as heralds of scabies.

The most common sites of involvement are webs of the fingers, wrists, elbows, anterior axillary folds, nipples, umbilical area and groins.

The primary lesion of scabies is a burrow. It appears as a wavy dark line with a papule or vesicle at the open end. The mite may be seen as a whitish dot at the closed end of the burrow.

The other lesions that may be seen are larval papules, nodules, pustules and vesicles.

Other members of the family are commonly affected.

Diagnosis

Scabies should be suspected in case of,

Itchy papules or nodules involving the classical sites.
History of itching at night.
History of similar complaints in other family members.

Diagnosis is confirmed by the demonstration of the mite, its eggs or fecal pellets.

Treatment Modalities

Permethrin 5% is the drug of choice, which can be used for all ages and on all body areas. It is used as a single application, washed off after 8 to 12 hours and may be repeated after one week.

GBHC 1% (Gamma benzene hexachloride) can be used once in 12 hours. But, it is not recommended for children, pregnant women, lactating women and those with neurological and extensive cutaneous diseases.

Benzyl benzoate lotion 25% (12.5% in case of children) can be used. It should be applied and left on the body for at least 48 hours or its application is repeated for three consecutive nights and is then washed off.

Sulfur (6% precipitated sulfur in petrolatum) is another option of treatment. It should be applied to the entire body below the neck daily for three days and the patient should take bath after 24 hours of each application. It is the drug of choice in pregnant women.