modified from: Service, M.W. (1980). A guide to Medical Entomology. Macmillan. London.
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Pediculus humanus, or the body/clothing louse is a blood sucking species of louse that can live between the skin and clothing of humans. This host specific ectoparasite of humans is thought to have evolved from head lice (Pediculus capitis) but migrated to the body in association with the wearing of clothes. Body lice are small flattened insects with a slightly elongated lobed abdomen, a distinct head, small eyes, a pair of short antennae and six legs, each terminating in a strong claw. Each of these stout claws has a small thumb-like spine for grasping, enabling the louse to move quickly around the clothes utilising the fibres of the fabric or body hair for support. Adult lice are 2-4mm in length, grey in colour, but redden after blood feeding. The mouth parts are tube-like, armed with minute teeth and sharp stylets for piercing the skin, and when not in use, are telescoped within the head. Adult lice and the three nymphal (immature) stages live their entire life within the clothing of humans. Lice may only leave the clothes briefly or hold onto the fibres of clothes or body hair whilst blood feeding. The lice blood feed frequently, at any time, day or night, but usually when the person is at rest. These parasites prefer to feed where the skin is soft and folded and the clothing fabric is in close contact with the body.
Female body lice will lay their eggs (or nits) along the seams or hems of clothes (especially underwear) that are adjacent to the surface of the skin. Each egg is firmly glued to fibres of the clothes, but occasionally body hair maybe used. A mature female louse will lay 200-300 eggs within her life span of a month, laying between 6-9 eggs a day. The eggs are white and oval in shape and rounded at the top. Eggs hatch within 5-10 days, but if the clothing is removed each night from the warmth of the body, development time is increased and the eggs may take up to 2 weeks before hatching. Louse eggs can remain viable for up to 14 days. Body lice are extremely sensitive to change in temperature and humidity and have been known to abandon a dead person or people with elevated temperatures. Without a constant source of blood, the lice perish within 2-5 days. In hot weather, when several layers of infested clothing are worn, the lice may move to an outer layer where the temperature is cooler. Lice are very rarely seen crawling on the outside of infested clothes, if they are visible it is an indication the individual is heavily infested. Normally body lice are sensitive to light and if disturbed will quickly move to a seam or crease for cover.
Transmission of body lice occurs when living conditions are crowded, personal hygiene is neglected, clothes are not changed and facilities for laundering clothes are not available. Lice can spread rapidly through homeless people or victims of war and natural disasters, when people sleep in their clothes and huddle together for warmth. Bedding and furniture have also been implicated as a source of infestation in overcrowded environments.
Initially, bites from body lice are seen as small minute red dots that develop into papular lesions with wheal-like inflammation. The toxic effects from repeated injections of saliva may produce symptoms including headache, lassitude, loss of appetite, joint pain, elevated temperature, irritability, and a rash which is similar to German measles. Severe itching is another symptom that infected individuals suffer, which may indicate the development of an allergy; inhalation of faeces or parts of cast skins from body lice may also trigger symptoms which resemble hay fever. Secondary infections are common and result from the continuous scratching of repeated inoculations of louse saliva. A prolonged infestation of body lice can result in thickening and pigmentation of the skin and is often referred to as "vagabondss disease". Body lice are not responsible for the spread of any infectious disease-causing organisms within Australia, and are considered uncommon in this country.
Identification of louse specimens is by light microscopy. Detail from the patient on exactly what part of the body the specimens were collected is important in establishing the identity of the louse. Head lice, Pediculus capitis (see Head Lice), are taxonomically very difficult to differentiate from body lice. Body lice are rarely found on the head of an infected person and, when not on the body, tend to stay hidden within layers of clothes.
Pubic lice, Pthirus pubis, (see Pubic Lice), are usually found attached to the hair in the pubic and perianal areas of the body, but are taxonomically very different to the body and head louse, and are readily identified.
Treatment & Control
Body lice are relatively easy to control by implementing a few simple steps. Regular changing and laundering of clothes (especially underwear), or disposal of affected clothing, will control lice. Using a hot water wash on clothes, followed by ironing will ensure all lice and nits have been killed. An increased level of personal hygiene with regular bathing or showering is essential for control. Dry cleaning or tumble drying affected items at >60oC for 15 minutes is another method of effectively killing lice and eggs.
If laundering facilities are not available dusting clothes with an insecticidal powder or fumigant are options that could be considered to aid in the control of lice; as a last resort, storage of clothes in a plastic bag should see all lice and eggs dead after a month.
Confirmation and Enquiries
Identification of body and other human lice, and all other medically important insects, is performed through the Medical Entomology Department at ICPMR, Westmead Hospital.
See 'Contacts' for further information.
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