The body louse ( Pediculus humanus humanus, also known as Pediculus humanus corporis) or clothing louse,
Body lice may lay eggs on the host's hairs and clothing,
Since body lice cannot jump or fly, they spread by direct contact with another person or more rarely by contact with clothing or bed sheets that are infested.
Body lice are disease vectors and can transmit pathogens that cause human diseases such as epidemic typhus, trench fever, and relapsing fever.
Life cycle and morphology
Pediculus humanus humanus (the body louse) is indistinguishable in appearance from
Pediculus humanus capitis (the
head louse), and the two subspecies will interbreed under laboratory conditions.
In their natural state, however, they occupy different habitats and do not usually meet.
They can feed up to five times a day.
Adults can live for about thirty days, but if they are separated from their host they will die within two days.
If the conditions are favorable, the body louse can reproduce rapidly. After the final molt, female and male lice will mate immediately. A female louse can lay up to 200–300 eggs during her lifetime.
The life cycle of the body louse consists of three stages: egg, nymph, and adult.
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Eggs (also called nits, see head louse nits) are attached to the clothes or hairs by the female louse, using a secretion of the accessory glands that holds the egg in place until it hatches, while the nits (empty egg shells) may remain for months on the clothing. They are oval and usually yellow to white in color and at optimal temperature and humidity, the new lice will hatch from the egg within 6 to 9 days after being laid.
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A nymph is an immature louse that hatches from the egg. Immediately after hatching it starts feeding on the host's blood and then returns to the clothing until the next blood-meal. The nymph will molt three times before the Imago louse emerges. The nymph usually takes 9–12 days to develop into an adult louse.
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The adult body louse is about 2.5–3.5 mm long, and like a nymph it has six legs. It is wingless and is tan to grayish-white in color.
The two P. humanus subspecies are morphologically quite identical. Their heads are short with two antennae that are split into five segments each, compacted thorax, seven segmented abdomen with lateral paratergal plates.
Origins
The body louse, it was thought, diverged from the head louse around 107,000 years ago, and this established the latest date for the adoption of clothing by humans.
[ Archive] However, recent transcriptome analyses casts doubt on whether lice provide a means to date the origin of clothes since it has found that "body and head lice were almost genetically identical. Indeed, the phenotypic flexibility associated with the emergence of body lice, is probably a result of regulatory changes, perhaps epigenetic in origin, triggered by environmental signals."
Body lice were first described by Carl Linnaeus in the 10th edition of Systema Naturae. The human body louse had its genome sequenced in 2010, and at that time it had the smallest known insect genome.
The body louse belongs to the phylum , class , order Psocodea and family Pediculidae. There are roughly 5,000 species of lice described, with 4,000 parasitizing birds and an additional 800 special parasites of mammals worldwide.
Signs and symptoms
Since an infestation can include thousands of lice, with each of them biting five times a day, the bites can cause strong itching, especially at the beginning of the infestation, that can result in skin excoriations and secondary infections.
If an individual is exposed to a long-term infestation, they may experience apathy, lethargy and fatigue.
Treatment
In principle, body louse infestations can be controlled by periodically changing clothes and bedding. Thereafter, clothes, towels, and bedding should be washed in hot water (at least ) and dried using a hot cycle.
The itching can be treated with topical and systemic
and
.
In case of secondary infections, antibiotics can be used to control the bacterial infection. When regular changing of clothes and bedding is not possible, the infested items could be treated with
.
Diseases caused
Unlike other species of lice, body lice can act as vectors of disease. The most important pathogens which are transmitted by them are
Rickettsia prowazekii (causes
epidemic typhus),
Borrelia recurrentis (causes
relapsing fever), and
Bartonella quintana (causes
trench fever).
Epidemic typhus can be treated with one dose of doxycycline, but if left untreated, the fatality rate is 30%.
See also
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List of parasites of humans
External links
