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Scabies

What is scabies?

Commonly called the “itch”, scabies is caused by a tiny mite (a minute arachnid) named Sarcoptes scabiei, of which there is a male and female gender. Copulation takes place on the skin surface, after which the fertilized female quickly burrows under the skin to begin deposition of her eggs; a process that can result in laying from 10-25 eggs over a period of 1-2 months. The female eventually dies in the extended burrow she created. Her larvae will hatch 3-4 days after being deposited, molt and then leave the burrow for the surface. There they will copulate and the newly fertilized females will burrow into the skin to repeat the cycle. Experts believe the intense itching is caused by the development of an allergic reaction to the mite, mite feces and mite eggs...pretty gross sounding, but fear not…read on.

What are the signs and symptoms of scabies infestation?
Small (1-2 mm diameter) red scabbed bumps, sometimes w/associated burrow markings that are located in one or more of the following areas: sides and web spaces of the fingers, the flexor aspects of the wrists, the extensor aspects of the elbows, anterior and posterior axillary folds, periumbilical region, anterior and lateral waistline, the extensor surface of the knees, the lower portion of the buttocks and nearby area of thighs, and the lateral sides of the feet. In females the area adjacent to the nipples, and in men the genitalia may be affected. The back is typically non-involved; the head is generally spared in adolescents and adults. 
scabies

Intense itching is the most frequent complaint; typically worsened at night and often over much of the body.Excoriation sores on the body may be caused by scratching. These sometimes become secondarily infected with bacteria due to incessant scratching.  

How is scabies transmitted?
Scabies is not an indication of bad hygiene or nutritional deficiency. It is transmitted by direct, prolonged, skin-to-skin contact with a person already infested with scabies.  (A quick handshake or hug will usually not spread infestation.)  Sexual partners, family members, schoolmates, teammates, and roommates are likely candidates for infection.  Infestation may also occur by sharing contaminated clothing, towels and bedding. While pets can harbor scabies and appear symptomatic for itch, animal infestation is of a different subspecies and rarely causes significant problems to humans, as the animal subspecies does not burrow and reproduce on human hosts.


How long after exposure will symptoms begin?
For a person who has never been infested with scabies, symptoms may take 4-6 weeks to begin.  For a person who has previously had scabies, symptoms appear within several days, likely due to sensitization of the immune symptom at time of earlier infestation. You do not become immune to subsequent infestations.

How is scabies diagnosed?
Diagnosis is most commonly made by visual examination for burrows or rash typical to scabies infestation.  A skin scraping may be taken followed by microscopic identification if diagnosis remains unclear. They will look for mites, eggs or mite fecal matter to confirm the diagnosis.

Treatment of Scabies
Currently the most effective treatments are Permethrin 5% Cream (Elimite or Acticin) or Lindane 1%. Permethrin is least neurotoxic and is safe for adults, adolescents, infants, children and even pregnant women, and therefore generally tried first. Always follow the directions provided by your physician or the directions on the package insert.  Massage the cream thoroughly from the neck down to the toes and soles of feet. Leave on for at least 8 hours (but no longer than 14 hours), then take a bath or shower to wash off them medication. Put on clean clothes. One treatment with Permethrin typically eradicates all mites and eggs from the body. A variety of other medications besides Permethrin are available for treatment of scabies, however due to potential side effects and cautions, these warrant further conversation with you healthcare provider to assure they are safe for you. Itching may take several days or even weeks to resolve completely even after effective treatment and eradication of the mites and eggs. Antihistamines (such as Benadryl/diphenhydramine or Zyrtec/cetirizine) and over the counter 1% hydrocortisone cream may help reduce itching. Antihistamines can cause drowsiness which needs to be taken into consideration with concurrent use of other sedating medications, driving and use of Alcohol or recreational drugs. Topical steroid should be used strictly per label medication instructions to avoid potential for permanent weakening of skin integrity. In order to lessen likelihood of re-infestation, any clothing or bed linens use in the past 4-5 days should be washed and dried using hot cycles, dry-cleaned, or placed in a sealed, plastic bag for 3 days.

Who should be treated?
Anyone who is diagnosed, as well as his or her sexual partners and persons who have close skin to skin contact, or frequent sharing of clothing/bedding should be simultaneously treated.  It is rarely necessary to repeat the treatment, but if new evidence of scabies is noted 2 weeks after initial treatment, one should consider re-treatment.

For more information, see the CDC web site at: www.cdc.gov/parasites/scabies