Pubic lice (crabs) - including symptoms, treatment and prevention

This is infestation of the pubic hair by the pubic or crab louse, Phthirus pubis. In heavy infestations they may be found in other hairy parts of the body, especially the armpits and eyebrows. They are different from head lice.

How pubic lice are spread

Transmission is mostly during sexual contact, but they can be spread on bedding, clothing or by close non-sexual body contact.

Symptoms

The main symptom is itching in the genital area.

Diagnosis

The lice can be seen with the unaided eye or more clearly with a magnifying glass. The greyish-white adults are about 2 mm long and almost as broad, with thick legs, and resemble a crab in appearance. They lay their eggs on pubic hairs and spend their entire life on the human host, feeding by sucking blood. They cannot survive without a human host.

Incubation period

(time between becoming infested and developing symptoms)

The eggs usually hatch in 7 days and adult lice live for about 30 days. It may take up to 1 month for symptoms to develop, as the person develops an allergic reaction to the saliva injected by the louse when biting.

Infectious period

(time during which an infested person can spread the lice to others)

While there are living adult lice on an infested person the lice can be passed on.

Treatment

Insecticidal creams and lotions may be obtained from pharmacies. They should be used strictly according to directions and treatment repeated after a week to kill any lice which may have hatched since the first treatment. They should not be used around the eyes. This area may be treated with petroleum jelly twice a day for 8 days. Consult your doctor for treatment of severe itching or if the bites become infected.

Prevention

  • Sexual partners should be treated at the same time as the case.
  • wash bedding, all clothing including night clothes and bath towels used while infestation was present in hot, soapy water, or dry clean
  • testing to exclude other sexually transmitted infections (STIs) is advisable as people infested with pubic lice will have another sexually transmitted infection.

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