Crab lice
Crab lice, scientifically known as Pthirus pubis, are small parasitic insects that primarily inhabit the pubic region of humans, but can also be found in other areas with coarse hair, such as the armpits and eyelashes. These parasites are commonly referred to as "crabs" due to their resemblance in shape and size. Crab lice are typically transmitted through close personal contact, particularly during sexual activity, but can also spread through sharing personal items like towels or bedding, though this is less common.
Symptoms of infestation include intense itching, blue-gray spots on the skin, and potential skin infections resulting from scratching. Diagnosis is generally made through a physical examination by a healthcare professional. Treatment for crab lice usually involves topical medications such as permethrin or pyrethrins, and in some cases, oral ivermectin may be prescribed.
Preventive measures include limiting sexual partners, maintaining cleanliness of personal items, and informing sexual partners if one is infected. Since crab lice can pose social and health-related challenges, awareness and education are essential for effective management and prevention.
Crab lice
- ANATOMY OR SYSTEM AFFECTED: Genitalia, hair, skin
- ALSO KNOWN AS: Pubic lice
Definition
Crabs are tiny, barely visible parasites (Pthirus pubis) that live in the pubic area of humans and cause itching. (The word “lice” is plural, and the singular is “louse.”) Pubic lice are commonly called crabs because they are shorter and rounder than head and body lice, making them resemble crabs. They are usually found in pubic hair but can also be found in other body areas with short hair (such as eyelashes, eyebrows, armpits, and mustaches).
Causes
Crabs are spread by personal contact, usually during sexual activity. They also may be spread by sharing personal items, such as bedding, towels, and clothing; however, this form of transmission is less common.
Risk Factors
Risk factors for crab lice include sexual contact with people with crabs and contact with contaminated items (fomites), such as bedding, towels, clothing, toilet seats, and furniture.
Symptoms
Symptoms of crab lice include itchiness (from mild to severe), tiny blue-gray bumps called macula caerulea stuck to the skin, skin breaks, and possible bacterial infection (caused by scratching).
Screening and Diagnosis
A doctor will ask about symptoms and medical history and perform a physical exam. They will examine the patient’s pubic area for lice, lice eggs (called nits), and macula caerulea.
Treatment and Therapy
Treating crabs involves applying over-the-counter shampoo or cream rinse containing permethrin or pyrethrins. For resistant cases, the doctor may prescribe topical malathion (a highly effective medication approved only for persons older than six). In the twenty-first century, oral ivermectin is also prescribed. Doctors once prescribed lindane, but it is no longer used because of the risk of serious side effects, such as seizures and neurological damage.
Lindane, a second-line treatment, was once prescribed to people who were unable to take other medications or who had not responded to them. According to the US Food and Drug Administration, lindane can cause serious side effects, including seizures and death. Those especially susceptible are infants, older people, children and adults weighing under 110 pounds, and persons with other skin conditions. Lindane is a toxin. Infected persons were given small amounts (1 to 2 ounces) of the shampoo or lotion and were instructed to apply a thin layer and not to reapply. Due to the risk of these serious side effects and the advent of newer medications, lindane is rarely used in the twenty-first century.
If other medications have failed, a doctor can prescribe oral ivermectin, which works to paralyze and kill the lice.
Treatment steps include washing the infested area and then towel drying. Thoroughly saturate hair with lice medication. If using permethrin or pyrethrins, leave the medication on for ten minutes. Thoroughly rinse off the medication with water. Dry the hair with a clean towel.
Following treatment, most lice eggs will still be attached to hair shafts. The lice eggs can be removed with fingernails or tweezers. Following treatment, one should put on clean underwear and clothing. If lice are in the eyebrows, the eyebrows should be coated thoroughly with petroleum jelly.
To kill any lice and nits that may be left on clothing or bedding, all items used during the two to three days before treatment should be washed in hot water (130° Fahrenheit) and dried using the hot cycle for a minimum of twenty minutes. Clothing that is not washable should be dry-cleaned.
One should avoid sexual activity until partners have been treated. The condition can be treated again in seven to ten days if necessary.
Prevention and Outcomes
To reduce the chance of getting crabs or spreading crabs, one should limit sexual partners and watch for signs of crabs, such as itching in the genital area. At home, one should thoroughly wash and dry bedding, towels, and clothing, and vacuum carpets, rugs, and upholstered furniture. Any person who has had crabs should inform their sexual partner that they are at risk for crabs. Also, one should avoid sexual activity until all partners have been treated.
Bibliography
"About Pubic 'Crab' Lice." CDC, 4 June 2024, www.cdc.gov/lice/about/pubic-lice.html. Accessed 27 Sept. 2024.
Berger, Stephen A., and John S. Marr. Human Parasitic Diseases Sourcebook. Sudbury, Mass.: Jones and Bartlett, 2006.
Despommier, Dickson D., et al. Parasitic Diseases. 5th ed., New York: Apple Tree, 2006.
Diaz, J. H. "Crab Lice (Pediculosis pubis)." Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John E. Bennett, and Raphael Dolin. 7th ed., New York: Churchill Livingstone/Elsevier, 2010.
Pickering, Larry K., et al., editors. Red Book: 2009 Report of the Committee on Infectious Diseases. 28th ed., Elk Grove Village, Ill.: American Academy of Pediatrics, 2009.
"Treatment of Pubic Lice." CDC, 8 Apr. 2024, www.cdc.gov/lice/treatment/pubic-lice.html. Accessed 27 Sept. 2024.
Weedon, David. Skin Pathology. 3d ed., New York: Churchill Livingstone/Elsevier, 2010.