The body louse (''Pediculus humanus humanus'', also known as ''Pediculus humanus corporis'') is a
hematophagic
Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice by certain animals of feeding on blood (from the Greek words αἷμα ' "blood" and φαγεῖν ' "to eat"). Since blood is a fluid tissue rich in nutritious pro ...
ectoparasite louse
Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result o ...
that infests humans. It is one of three lice which infest humans, the other two being the
head louse
The head louse (''Pediculus humanus capitis'') is an obligate ectoparasite of humans. Head lice are wingless insects that spend their entire lives on the human scalp and feeding exclusively on human blood. Humans are the only known hosts of th ...
, and the
crab louse or pubic louse.
Despite the name, body lice do not directly live on the host. They lay their eggs on fibres of clothing and only come into contact with the host whenever they need to feed. 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
Trench fever (also known as "five-day fever", "quintan fever" ( la, febris quintana), and "urban trench fever") is a moderately serious disease transmitted by body lice. It infected armies in Flanders, France, Poland, Galicia, Italy, Salonika, Ma ...
, and
relapsing fever
Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus '' Borrelia'', which is transmitted through the bites of lice or soft-bodied ticks (genus ''Ornithodoros'').
Signs and symptoms
Most people who ar ...
. In developed countries, infestations are only a problem in areas of poverty where there is poor body hygiene, crowded living conditions, and a lack of access to clean clothing.
Outbreaks can also occur in situations where large groups of people are forced to live in unsanitary conditions. These types of outbreaks are seen globally in prisons, homeless populations, refugees of war, or when natural disasters occur and proper sanitation is not available.
Life cycle and morphology
''Pediculus humanus humanus'' (the body louse) is indistinguishable in appearance from ''Pediculus humanus capitis'' (the
head louse
The head louse (''Pediculus humanus capitis'') is an obligate ectoparasite of humans. Head lice are wingless insects that spend their entire lives on the human scalp and feeding exclusively on human blood. Humans are the only known hosts of th ...
), 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 and as adults can live for about thirty days, but if they are separated from their host they will die within a week. 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.
# Eggs (also called nits, see
head louse nits) are attached to the clothes 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.
# 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
adult louse emerges. The nymph usually takes 9–12 days to develop into an adult louse.
# 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
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
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 diverged from the head louse around 170,000 years ago, implying an earliest date for the adoption of clothing by humans.
[Archive](_blank)
/ref> Body lice were first described by Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
in the 10th edition of ''Systema Naturae
' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...
''. The human body louse had its genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
sequenced in 2010, and at that time it had the smallest known insect genome.
The body louse belongs to the phylum Arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
a, class Insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
a, order Phthiraptera
Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result of ...
and family Pediculidae
''Pediculus'' is a genus of sucking lice, the sole genus in the family Pediculidae. ''Pediculus'' species are ectoparasites of primates.
Species include:
*''Pediculus clavicornis'' Nitzsch, 1864
*''Pediculus humanus'' Linnaeus, 1758
**''Pediculu ...
. There are roughly 5,000 species of lice described, 4,000 are parasitizing birds, while additional 800 are 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, he or she 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 corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...
s and antihistamine
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provid ...
s. In case of secondary infections, antibiotics can be used to control the bacterial infection. When changing regularly of cloths and bedding is not possible, the infested items could be treated with insecticides.
Diseases caused
Unlike other species of lice, body lice can also act as vectors of disease. The most important pathogens which are transmitted by them are ''Rickettsia prowazekii
''Rickettsia prowazekii'' is a species of gram-negative, alphaproteobacteria, obligate intracellular parasitic, aerobic bacillus bacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the ...
'' (causes epidemic typhus), ''Borrelia recurrentis
''Borrelia recurrentis'' is a species of ''Borrelia'', a spirochaete bacterium associated with relapsing fever. ''B. recurrentis'' is usually transmitted from person to person by the human body louse
The body louse (''Pediculus humanus humanu ...
'' (causes relapsing fever
Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus '' Borrelia'', which is transmitted through the bites of lice or soft-bodied ticks (genus ''Ornithodoros'').
Signs and symptoms
Most people who ar ...
), and ''Bartonella quintana
''Bartonella quintana'', originally known as ''Rochalimaea quintana'', and "''Rickettsia quintana''", is a bacterium transmitted by the human body louse that causes trench fever. This bacterial species caused outbreaks of trench fever affecting 1 ...
'' (causes trench fever
Trench fever (also known as "five-day fever", "quintan fever" ( la, febris quintana), and "urban trench fever") is a moderately serious disease transmitted by body lice. It infected armies in Flanders, France, Poland, Galicia, Italy, Salonika, Ma ...
).
Epidemic typhus can be treated with one dose of doxycycline
Doxycycline is a broad-spectrum tetracycline class antibiotic used in the treatment of infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, Lyme disease, cholera, typhus, an ...
, but if left untreated, the fatality rate is 30%. Relapsing fever can be treated with tetracycline
Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis.
Common side effects in ...
and depending on the severity of the disease, if left untreated it has a fatality rate between 10 and 40%. Trench fever can be treated with either doxycycline or gentamicin
Gentamicin is an antibiotic used to treat several types of bacterial infections. This may include bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not e ...
, if left untreated the fatality rate is less than 1%.
See also
* List of parasites of humans
Endoparasites Protozoan organisms
Helminths (worms)
Helminth organisms (also called helminths or intestinal worms) include:
Tapeworms
Flukes
Roundworms
Other organisms
Ectoparasites
References
{{Portal bar, Bio ...
References
External links
Body and head lice
on the UF/ IFAS Featured Creatures Web Site
{{Authority control
Ectoparasites
Insects described in 1758
Lice
Parasitic arthropods of humans
Taxa named by Carl Linnaeus