Natural History
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.
Clinical Presentation
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 "vagabonds’s
disease". Body lice are not responsible for the spread of
any infectious disease-causing organisms within Australia, and
are considered uncommon in this country.
Laboratory Diagnosis
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.
