Crabs

What are crabs?

Pubic lice, commonly referred to as "crabs", are parasites (small insects) that have a particular preference for pubic hairs (where they establish themselves). Also known as pediculosis pubis or phthirus pubis, they may be found attached to the short hairs in other body regions (the anus, armpits, beard, eyebrow and eyelashes). They are cousins of head lice.

How are crabs transmitted?

This infection is primarily transmitted through sexual relations with an infected partner – penetration is not required for transmission. Oral sex with a contaminated partner can lead to infestation of the eyebrows, eyelashes and/or scalp hair. Transmission may also occur via simple (non-sexual) contact with an infected individual or via indirect contact with contaminated objects (including clothing, bedding, towels and/or toiletries, etc.) This particular parasite can survive away from the human body (the host) for periods of up to 24 hours.

What is the lifecycle of crabs?

The incubation period (the time between contact and the appearance of symptoms) typically varies from several days up to several weeks, and this according to the quantity of lice transmitted. Early on, one can identify small brown-colored organisms that are immobile and firmly attached to the hairs via their extremely strong claws (like a crab). One may also notice the presence of pale or white-colored eggs on the surface of the skin – these are often mistaken for flaking or dry skin. Under ideal conditions, the eggs will hatch within 7 to 10 days. A larva or baby louse emerges and attaches itself to a hair (called a nit). The young louse matures into its adult form within 8 to 10 days. Once an adult the parasite can mate and reproduce within 10 hours and this until its death 6 weeks later. The female crab can lay approximately 4 eggs per day. Both the baby and adult louse feed on human blood and will die if deprived of blood for more than 24 hours.

What are the symptoms of crabs?

Symptoms commence approximately 2-3 weeks after contamination. The symptoms of crabs are primarily dermatological: localized itchiness (pruritus) of the affected regions, whether in the genital or other hirsute (hairy) skin zones. At times a patient may observe tiny blood stains in their underwear – this may signal the presence of the parasite before the itchiness begins. Itchiness is caused by the penetration of the local skin by the bug – in order that its eggs may be laid (small red spots). Minute pale brown insects or their pale whitish eggs may be visible if you look close enough.

How does an HIV/AIDS infection interact with crabs?

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 crabs diagnosed?

Crabs are easy to recognize given their characteristic appearance (a crab – see the lifecycle section). They are best observed under the microscope. Your physician may remove a crab from its home at the base of a hair and place it on a microscope slide – the beast is then drowned with a drop of immersion oil (used for microscope procedures). The pregnant female is quite impressive!

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

Is there a treatment for crabs?

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 crabs?

• All sexual partners;
• All close contacts and family members;
• All those individuals who share clothing, bedding or toiletry articles.

How can people with crabs 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 infections.