Introduction
Louse infestation is a problem that is faced worldwide, making diagnosis and treatment planning a common task for medical practitioners. Louse infestation can be seen in people of all ethnic groups, races, and socioeconomic levels. Different types of lice feed on different parts of the body. Phthirus pubis is known as the pubic lice or crabs and is found majorly in the pubic hair.
What Is Phthiriasis?
Phthiriasis is an infestation caused by Phthirus pubis; and usually infests the pubic region and may also be seen in the buttocks, groin, perianal and intergluteal region. Less commonly, it may also be seen in the chest hair, armpit, eyelashes, and thighs in hairy individuals. It may even be seen on the scalp, but very rarely. The condition is manifested as intense itching in the groin, especially at night.
What Causes Phthiriasis?
Phthiriasis is caused by Phthirus pubis, also known as crabs or pubic lice, an ectoparasite that feeds on blood and is exclusively seen in humans. Adult pubic lice are 1.5 to 2 mm long and are comparatively broader than head and body lice. The insect is gray to white in color and lives for approximately two weeks on the host body. Outside the host body, they only survive for 24 to 48 hours without a blood feed. These move from person to person through sexual contact or bedding, clothes, and towels.
How Does Phthiriasis Spread?
Phthiriasis is spread from person to person through sexual contact - vaginal, oral, or anal sex - protected and unprotected sex. It may also spread through bedding, clothes, and towels. It is common in crowded places, where the distance between people is very less, allowing the lice to crawl from one person to another. And also in families with poor hygiene practices. Unlike other body lice, the crab louse does not jump from one host to another. The maximum distance the lice can travel is 25 cm on the body. The lice do not spread through toilet seats, as may be commonly misunderstood since they can not walk over smooth surfaces and can not survive for more than 24 to 48 hours without a blood feed. An infestation in children or teenagers indicates sexual exposure or abuse.
What Are the Signs and Symptoms of Phthiriasis?
The characteristic symptom of phthiriasis is a feeling of something moving in the hair and intense itching, redness, and inflammation, especially in the pubic area. This is due to the allergic reaction to the saliva of the feeding lice. In some cases, a bluish-gray discoloration is seen in the feeding site, which may persist for a few days. Louse droppings may be seen as black powder on clothes and underwear. Visible nits (lice eggs) may also be seen on the hair base ends and crawling lice. Phthiriasis infestation on the eyelids may present as intense itching of the eyelids, red, watery eyes, and loss of lashes. Phthirus pubis is mostly never a vector of secondary infection, but a secondary bacterial infection may occur from scratching the skin.
How Is Phthiriasis Diagnosed?
Phthiriasis is diagnosed by carefully examining the skin and base of the hair for adult and young lice and nits, majorly in the pubic region and less commonly in the beard, chest, mustache, eyelids, and eyebrows. The pubic lice may be seen grabbing onto more than one hair follicle and usually do not crawl as much as other body lice. However, if not found crawling, small nits or lice eggs may be observed attached to the base of the hair. The health care provider might use a dermatoscope, a stereo-microscope, or a magnifying glass to identify the lice.
How Is Phthiriasis Treated?
To treat pubic lice, a lotion containing 1% Permethrin or Pyrethrins and Piperonyl butoxide may be used to kill the lice in the infected area. These are available over-the-counter, do not require a prescription, and are safe to use if used according to the instructions in the package.
Another treatment option would be Lindane shampoo. However, it is not recommended as a first-line therapy since it harms the brain and nervous systems. Hence, Lindane shampoo is not recommended for premature infants, pregnant or breastfeeding women, people with seizure issues, and people allergic to lindane shampoo. It is only used if no other treatment options are successful or for patients who can not tolerate other medications that may have lesser risk. Topical Ivermectin can also be used to kill the lice and is approved by the U.S food and drug administration (FDA).
For Phthirus pubis on the eyelashes and eyebrows: Gently pick the lice out using hands, forceps, or a nit comb. If additional treatment is required, careful application of ophthalmic-grade Petrolatum ointment to the eyelid margins is recommended.
What Are the Complications of Phthiriasis?
Complications of phthiriasis may be majorly due to intense itching; it can cause thickening of the skin, darkening of the area, and secondary bacterial infection of the area - like impetigo, conjunctivitis, and blepharitis.
How to Prevent Phthiriasis?
Phthiriasis can be prevented by following a few steps:
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Avoid sexual contact with an infected partner until examined and treated adequately and the infestation is ruled out completely.
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All the sexual partners of the infected person must be examined and treated to prevent the spread of the infestation.
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Wash and dry clothes used by an infected person at high heat. For clothes that can not be washed, dry clean or store them in a sealed bag for two weeks.
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Avoid sharing clothing, bedding, and towels with an infected person.
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Please refrain from using fumigant sprays or fogs, as they may not be effective against pubic lice. It may also be toxic if one inhales it or is absorbed through the skin.
Conclusion
Phthiriasis is a louse infestation seen worldwide and usually infects the pubic regions. It may also be seen in the buttocks, perianal region, and less commonly in the armpit, eyelashes, eyebrows, chest hair, etc. It is caused by Phthirus pubis, which hosts only humans and feeds on blood. It is contracted through sexual contact and is characterized by intense itching in the pubic region. The condition can be prevented by avoiding sexual contact with an infected person and adopting appropriate treatment modalities.
