Scabies

What are scabies?

Scabies is one of the most frequent skin infections in North America. The last several years have evidenced a resurgence of this infestation. Scabies is also caused by an acarian parasite or mite that is invisible to the naked eye – sarcoptes scabei. This bug lives and feeds in the superficial layer of the skin, where it burrows around and lays its eggs.

How are scabies transmitted?

Scabies are transmitted in a fashion similar to crabs – frequently as a sexually transmitted infection (penetration is not required). In addition, this infection can spread readily and rapidly in closed environments (where there is close and/or prolonged contact) such as daycare centers, schools and nursing homes.

What is the lifecycle of scabies?

The female mite is drawn to the warmth of a potential host. She penetrates the skin and burrows in and begins to lay eggs (approximately 1-3 eggs per day). The presence of these eggs produces an inflammation similar to an allergic reaction – this is responsible for the intense itchiness. The eggs then hatch, mature into larvae and begin a new life cycle. Without treatment she can procreate for 5 weeks.

What are the symptoms of scabies?

Once the several week incubation period is complete, intense itchiness may manifest itself diffusely (usually begins in the body’s folds; armpits, buttocks, groin, etc.). This itchiness is typically worse at night. Minute burrows several millimeters long (corresponding to the migration of the parasite under the skin’s surface) appear between the fingers, on the wrists and ankles. Papules (pimples and bumps) may appear in the region of the armpits, the breasts, buttocks and genital organs. This latter manifestation is caused by an allergic reaction to eggs laid by the parasite.

How does an HIV/AIDS infection interact with scabies?

These parasitic infections are frequent in those patients infected with the HIV virus or symptomatic with AIDS. Symptoms are commonly atypical and may escape appropriate diagnosis. Treatment is at times resistant and difficult.

HOW ARE SCABIES DIAGNOSED?

The diagnosis of scabies is typically based on a classical symptom history accompanied by characteristic skin lesions identified by your physician (once again, intense itchiness, worse at night, bumps and burrows in common skin regions). The diagnosis of scabies may be difficult at times given that the visual signs may be subtle or may be confused with eczema. At times the diagnosis is based presumptively on your symptom history and is confirmed by your response to treatment. Your physician may apply a drop of mineral oil to a suspicious lesion and scrape the surface with a slide. Microscopic analysis may reveal the parasite, its eggs or feces. Your physician may use the "ink test", whereby a black-tip felt pen is applied to a suspicious lesion; if this is a burrow the ink will seep into the tract and help confirm the diagnosis.

When crabs or scabies are diagnosed as a sexually transmitted disease, a complete STI screening examination should be considered.

Is there a treatment for scabies?

There are effective lotions, creams and shampoos (i.e. Kwellada, Nix) that your physician may prescribe (follow the instructions carefully). It is important to change into clean clothes immediately after your treatment in order to avoid recontamination. Contaminated clothing, bedding and towels/toiletries must be washed for at least 20 minutes at 55 degree Celsius (see alternative eradication approaches below). This is crucial in preventing recontamination! It is often recommended to repeat the treatment 7 days after the initial product application. This is to ensure that treatment resistant eggs laid on the day of application be destroyed upon hatching – and thereby avoid a second cycle of infection. No product is 100 % effective at eliminating non-hatched eggs. It is not necessary to shave all body hair! Several aerosol products are available and may be used to treat contaminated objects that are not amenable to washing in hot water (sofas, carpets, mattresses and toiletry articles, etc.). If you are pregnant and infested, consult your physician to select a safe and appropriate treatment.

It is quite normal for the itchiness to persist for several days after an effective treatment. Nonetheless, if your symptoms persist for more than one month following treatment, it would be prudent to consult your physician.

What are the causes of treatment failure?

• An incomplete treatment application – not all hairy body parts are addressed;
• Non-treatment of close contacts – sexual partners, roommates, family members, etc.;
• A second application at 7 days is ignored;
• An inappropriate use of the product (please follow the directions!);
• Environmental eradication measures have been ignored (washing all clothing and bedding, etc.).

Who are at risk of contracting scabies?

Everyone is at risk of contracting scabies, from very young children to adults.

How can people with scabies prevent transmission?

• All sexual partners should be treated, regardless of whether or not they are symptomatic.
• Avoid sharing underwear, clothing and towels.
• Given that these parasites can be transmitted by casual close contact, all close friends and family members should be advised and treated at the same time (this includes all attendees of daycare centers, schools or nursing homes – when a case is identified).
• All clothing that has been worn, including bedding must be washed in hot water (55 degrees Celsius) for at least 20 minutes. Dry-cleaning, the application of an appropriate insecticide or the placement of articles into an airtight plastic bag for 24 hours is also deemed effective.
• While the condom does not prevent transmission of crabs or scabies (pubic hairs are not covered), they are effective at preventing other sexually transmitted diseases.