Body louse
The body louse (Pediculus humanus humanus, also known as Pediculus humanus corporis) or the cootie is a hematophagic ectoparasite louse that infests humans.[1] It is one of three lice which infest humans, the other two being the head louse, and the crab louse or pubic louse.[2]
This article is about the animal. For the infestation caused by body lice, see Pediculosis corporis.
Body lice may lay eggs on the host hairs and clothing,[3] but clothing is where the majority of eggs are usually secured.[4]
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.[5]
Body lice are disease vectors and can transmit pathogens that cause human diseases such as epidemic typhus, trench fever, and relapsing fever.[6] 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.[7] 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.[8]
Origins[edit]
The body louse diverged from the head louse around 170,000 years ago, establishing the latest date for the adoption of clothing by humans.[15][16][17][18] 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.[19] The body louse belongs to the phylum Arthropoda, class Insecta, order Phthiraptera 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.[20] Lice on mammals originate on a common ancestor that lived on Afrotheria that originally acquired it from via host-switching from an ancient avian host.[21]
Signs and symptoms[edit]
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.[5] If an individual is exposed to a long-term infestation, they may experience apathy, lethargy and fatigue.
Treatment[edit]
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 50 °C or 122 °F) and dried using a hot cycle.[22] The itching can be treated with topical and systemic corticosteroids and antihistamines.[23] 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 insecticides.[22]
Diseases caused[edit]
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%.[14] Relapsing fever can be treated with tetracycline and depending on the severity of the disease, if left untreated it has a fatality rate between 10 and 40%.[14] Trench fever can be treated with either doxycycline or gentamicin, if left untreated the fatality rate is less than 1%.[14]