Human louse – General Information

capitis

Corporis

pubis

Coloration

gray and white

tan to greyish white

translucent

Size

3 to 4 mm in length

4 to 5 mm in length

2 to 3 mm in length

Body parts

Mouth adapted to suck blood and legs adapted to grip hairs

six-legged, mouth adapted for blood sucking and claws for grasping

six-legged, with four legs resembling crab claws. Legs are adapted to grasp pubic hairs.

Fun Historical Facts About Pediculosis

Ancient Remedies for Pediculosis

• Evidence for the body louse was also recently discovered in the excavation of a fortress in Masada Israel, which was originally the storeroom for King Herod the Great. The store-room is believed to have housed soliders during the Jewish Revolt of 66 – 74 CE, which would have provided an ideal environment for a lice infestation.

• Combing or shaving hair (Ancient Egyptians)

• Aztec King Montezuma paid for his subjects to have their nits removed, and then he had them preserved.

• Drinking garlic concoctions (Greece)

• Military personnel in World War One helped control the spread of the disease typhus (commonly transmitted by body lice) by bathing soldiers and washing their clothes.

• Greek naturalist Pliny the Elder (23-79 CE) recommended destroying nits using dog’s fat or eating cooked serpents.

P. capitis:

Typically asymptomatic. Symptoms that may appear are itchiness of the neck, scalp and ears, pruritis, as well as puss in affected areas (bites). In more severe cases secondary bacterial infections can develop which may lead to febrile episodes as well as enlargement of the cervical and nucal lymph nodes.

P. corporis:

Itchiness and visible bite marks on the body and pruritis, especially around the waist and armpits. There may also be crusting and redness due to secondary bacterial infections.

P. pubis:

Itchiness in public areas and armpits is the most common complaint although not always a complaint. Pale blue spots at the follicular orifices may appear in the case of a prolonged infestation.

P. capitis

P. corporis

P. pubis

Clinical presentation of head, body and pubic lice. P. capitis presentation includes brown fecal matter around the ear. The P. corporis image is the clinical presentation of pruritis due to a prolonged lice infection. P. pubis were found attached to pubic hairs in the third image.

Transmission

• Human to human transmission is the only way pediculosis is transmitted. Transmission and infection are usually the results of low levels of personal hygiene

• Tranmission of head and body lice is common where crowds of people are in close contact, such as in schools, prisons and trenches.

• Contact with infected hair (i.e. sharing combs and/or hair brushes) can transfer head lice between individuals

• Contact with clothing and bedding facilitates the transfer of head, body and pubic lice between human hosts

• Sexual contact facilitates the transmission of pubic lice between individuals

Reservoirs

Humans are the only reservoir for all human lice species. Lice do not typically survive more than 30 days without a human host.

Vectors

There is no vector for pediculosis, but body lice have been known to act as vectors in the spread of other diseases such as typhus, trench fever and relapsing fever.

Life cycle of P. capitis

The adult female will lay her eggs (7-10 per day) near the hair shaft. The egg (nit) will take approximately 8 days to develop and emerge as a nymph. The nymph will mature into an adult louse in approximately 8 days and will then begin to feed and reproduce on the scalp, neck and eyes of the infected person.

P. corporis life cycle

P. pubis life cycle

The body louse follows a similar developmental and maturation pattern as the head louse. The adult body louse will then feed on the skin of the body of the infected individual but dwells and lays its eggs in the seams of the individuals clothing and/or bedding.

Pubic lice have a life cycle similar to both the head and body lice, although parallel the head lice more because the eggs are deposited near the base of the pubic hairs. The development and aturation of the nymph into an adult louse is similar to the development described in the diagram above.

Incubation Periods

The incubation period is the length of time the laying of the egg and the hatching of the Pediculus nymph.

P. capitis: 8 days

P. corporis: 6-10days

P. pubis: 6 – 8 days

P. capitis:

Identification of louse and nits. This can be aided with the use of a fluorescent Underwood light. Careful and thorough combing can also be done to search for nits and lice. Official measure of diagnosis is the presence of nits within 6.5 mm of scalp.

P. corporis:

Identification of louse or nits on clothing. The adult louse may hard to identify because they move quickly across the body and clothes.

P. pubis:

Identification of louse or nits in the pubic and armpit areas. Identification of the adult may be difficult because of its translucence.

The best preventative measure against all types of lice is to practice consistent and adequate measures of personal hygiene. This includes washing head and body hair in warm water (temperatures of greater than 130 degrees Fahrenheit may kill adult lice), as well as laundering clothing on a regular basis.

Other means of preventing the spread of pediculosis include not sharing personal hygiene items such as hair brushes and combs, as well as towels and unwashed clothing. One recommendation as a preventative measures for elementary-school aged children is to provide them with individual hooks for caps and coats to prevent the spread of head lice.

Body Lice

Hygiene:

Have infected individual bathe thoroughly. Be sure to wash clothes and bedding in warm water and dry in heat. Body lice can survive off of the body for 30 days so it is important to prevent re-infection by washing items that may have come in contact with infected person and his/her clothing.

Medications:

Lindane lotion may be recommended (washed off after 8 hours) . Corticosteroid creams can be used for pruritic and irritated areas, applied twice daily

Lice are found in countries all over the world, not excluding the most developed societies of Western Europe and the North America. Individuals from all socio-economic backgrounds can be affected by lice, although this is more true for head lice than body lice, which typically affect homeless individuals to a greater extent than individuals who have access to washing machines and hot baths. Head lice have infected elementary-aged school children in North America at epidemic proportions, and head lice infect more children than all other communicable diseases combined (6-12 million children infected each year).

                CDC recommendations for head lice outbreaks in schools:

• Inform the school of the infestation
• Treat all infected children for head lice – make sure to screen and track down the contacts of infected children
• Treat households by treating both infected people and cleaning clothing, bedding, towels and hair brushes and combs (wash in hot water and soap).
• Infected children may return to school 24 hours following hair treatment.
• Make sure school nurse or other officials inform parents of outbreak.
• When possible, avoid perpetrating stigma. Keep infected student’s names confidential.