[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 13 The Arthropods
313
Head and body louse
Crab louse
FIGURE 13-10 Comparison of adult head and body louse with crab louse.
TABLE 13-9
Adult Lice: Typical Features
at a Glance
FIGURE 13-11 Adult body louse (fresh preparation,
saline suspension, ×200).
Because they are sensitive to environmental
changes, lice spend most of their lives feeding, via
blood meals, on their respective hosts.
Epidemiology and Geography
Found worldwide, particularly in areas of poor
personal and general hygiene, lice are most commonly
transferred directly from person to person.
Outbreaks among schoolchildren are known to
occur when they share combs, scarves and hats.
Further children, particularly those in day care,
may bring the infestation home creating the
opportunity for the lice to spread to family
Parameter
Size
Mouth parts
Body
Legs
Antennae
Hair
Description
Head and body lice, 2-3 mm long
Crab lice, up to 2 mm long
Adapted for piercing human skin and
sucking blood
Head and body lice, three
segments—narrow head, thorax,
abdomen
Crab lice—plump; thorax and
abdomen appear as one section
Three pairs extending from thorax
with clawlike feet
One pair
Head and body lice—absent
Crab lice—present on extremities
members. Lice have the ability to migrate from
one host to another, with only slight person-toperson
body contact. Crab lice are primarily
transmitted through close personal contract,
expecially during sexual intercourse. Infected
clothing or other personal articles also serve as
sources of possible head, body, and crab lice
infections. In addition to being considered a nuisance
in their own right, lice are capable of transmitting
bacterial and rickettsial infections to
humans (see Table 13-13).