Crab louse Totally Explained

Everything about Pubic Lice totally explained

The pubic or crab louse (Phthirus pubis) is a parasitic insect which spends its entire life on human hair and feeds exclusively on blood. Humans are the only known host of this parasite. Humans can also be infested with body lice (Pediculus humanus humanus) and with head lice (Pediculus humanus capitis)

Morphology

The dorso-ventrally flattened body of the louse is divided into head, thorax and abdomen. A pair of eyes and a pair of antennae are clearly visible on the head. The mouthparts are adapted to piercing the skin and sucking blood. The second and third pair of legs, with their terminal claws are adapted to holding the hair-shaft, while the first pair of leg holds the skin during feeding. Abdominal protuberances on the side of the body are characteristic of this species. Males are slightly smaller than females. The eggs are oval-shaped and ca. 0.8 mm in length. Immediately after oviposition they're shiny, round, and transparent. Pubic lice are 1-2- mm in size, varying according to the stage of their development. They are usually whitish-grayish in color though they become reddish-brown for some time after a blood-meal.

Biology

Pubic lice are insect parasites, spending their entire life on the host's hair and skin and feeding exclusively on blood, 4-5 times daily. The life-cycle from egg to adult is 22-27 days. The egg hatches producing the first nymphal stage, which after three moltings develops to nymph 2, nymph 3 and subsequently to either a male or female louse. The incubation period of the egg is 7-8 days, while the rest of the cycle is taken up with the development of nymphal stages. The average adult female lives for 17 and the male for 22 days.
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Epidemiology

Pubic lice usually infect a new host only by close contact between individuals, making sexual contacts among adults and parent child interactions the more likely routes of infestation than shared towels, clothing, beds or closets. Adults are more frequently infested than children .

Diagnosis

A pubic louse infestation is usually diagnosed by carefully examining pubic hair for nits, nymphs and adults. Lice and nits could be removed either with forceps or by cutting the infested hair with scissors (with the exception of the eye area). A magnifying glass or a stereo-microscope can be used for the exact identification. If lice are detected in one family member, the entire family needs to be checked and only those who are infested with living lice should be treated.

Clinical Information

Although any part of the body may be colonized, crab lice favor the hairs of the genital (Fig. 1) and peri-anal region. Especially in male patients, pubic lice and eggs can also be found in hair on the abdomen (Fig. 2) and under the armpits as well as on the beard and mustache, while in children they're usually found in eye-lashes (Fig. 3). Infestation with pubic lice is called Phthiriasis or Pediculosis pubis, while infestation of eye-lashes with pubic lice is called Phthriasis palpebrarum . The main symptom is itching, usually in the pubic hair area. It results from hypersensitivity to louse saliva, and it becomes strong enough two or more weeks following initial infestation. In the majority of infestations a characteristic grey-blue or slate coloration appears (maculae caeruleae) at the feeding site, which may last for days and is also characteristic for the infestation. Pubic lice are primarily spread through sweat and body contact or sexual contact. Therefore, all partners with whom the patient has had sexual contact within the previous 30 days should be evaluated and treated, and sexual contact should be avoided until all partners have successfully completed treatment and are thought to be cured. Because of the strong association between the presence of pubic lice and classic sexually transmitted diseases (STD), patients diagnosed with pubic lice should undergo evaluation for other STDs. Infection in a young child or teenager may indicate sexual abuse. Image:Fig._1._Pubic_lice_in_genital_area.jpg|Fig.1 Pubic lice in genital area Image:Fig._2._Pubic_lice_in_abdomen.jpg|Fig.2 Pubic lice in abdomen Image:Fig._3._Pubic_lice_on_eye-lashes.jpg|Fig.3 Pubic lice on eye-lashes

Treatment

Crabs or Crotch Crickets can be treated with Permethrin 1% cream rinse and pyrethrins can be used for this purpose and are the drugs of choice for pregnant or lactating women. These agents should be applied to the affected areas and washed off after 10 minutes. Shaving off or grooming any hair in the affected areas with a fine-toothed comb is necessary to ensure full removal of the dead lice and / or nits, though it doesn't suffice as treatment on its own. Resistance of pubic lice to pyrethroids must be if at all very rare. A second treatment after 10 days is recommended. Pubic lice on the eyelashes can be treated with a permethrin formulation by applying the solution to the infested hair with an applicator. It is dangerous to remove lice or eggs in the eyelashes by plucking or cutting the hairs.
Lindane shampoo (1%), a pediculocide, is FDA approved as safe and effective when used as directed for the second-line treatment of pubic lice (crabs). While serious side effects have been reported, they're considered to be rare and have almost always resulted from misuse of medication, such as excessive application and oral ingestion. To minimize this risk, Lindane medications are now dispensed in small single-use bottles. The Centers for Disease Control and Prevention (CDC) notes that lindane shouldn't be used immediately after a bath or shower, and it shouldn't be used by persons who have extensive dermatitis, women who are pregnant or lactating or children aged under 2 years. The FDA similarly warns against use in patients with a history of uncontrolled seizures disorders and premature infants, and recommends cautious use in infants, children, the elderly, and individuals with other skin conditions (for example, atopic dermatitis, psoriasis) and in those who weigh less than 110 lbs (50 kg). Further Information

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