[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 13 The Arthropods
Clinical Symptoms
Symptoms of an infestation with lice, known as
pediculosis, include itchy papules at the infestation
site and a local hypersensitivity reaction,
followed by inflammation caused by the presence
of lice saliva and fecal excretions. Secondary bacterial
infections may also occur, resulting in a
mangelike lesion.
Treatment
Successful treatment of lice must destroy the
eggs and adults. The lice treatment of choice is
the direct application of benzene hexachloride
lotion.
Prevention and Control
Lice prevention and control measures include
proper personal and general hygiene practices
and prompt treatment of known lice infestations.
In addition, the complete and thorough cleaning
of all articles with which an infected person
might have come into contact is essential for
preventing further lice infestations.
Quick Quiz! 13-22
This type of louse is characterized by hair extremities.
(Objective 13-5)
A. Head louse
B. Body louse
C. Crab louse
D. Foot louse
Quick Quiz! 13-23
The typical life span for adult lice is which of the following?
(Objective 13-6)
A. 18 days
B. 24 days
C. 27 days
D. 30 days
Quick Quiz! 13-24
To treat lice infections successfully, which morphologic
forms are necessary to destroy? (Objective
13-10)
A. Eggs and larvae
B. Eggs and adults
C. Larvae and adults
D. Eggs, larvae, and adults
Mosquitoes
Morphology
More than 3000 documented species of mosquitoes
are known to exist (Fig. 13-12; Tables 13-10
and 13-11; also see Table 13-7). The typical adult
mosquito has a three-segmented body consisting
of a head, thorax, and abdomen. The roundish
head is connected to the elongate thorax by a
slender neck. The abdomen is also elongated in
shape and is comprised of 10 segments of its
own. Only eight of the abdominal segments are
usually visible. Each of the single pair of antennae
is long and has three segments. The three
pairs of legs extend from the thorax region. Mosquitoes
have two pairs of wings; one pair is
smaller than the other. Mosquitoes vary in size,
depending on the species. The Anopheles mosquito,
for example, generally measures 6 to
8 mm long. The key characteristics used to differentiate
the mosquito species, which are the
same as those for identifying flies, are listed in
Table 13-7. A detailed discussion of all mosquito
species is beyond the scope of this chapter. A
brief introduction to the mosquito, in general
terms, is the focus of this section.
Life Cycle Notes
Adult mosquitoes lay their eggs in water or on a
moist substance that eventually accumulates
water. Young larvae hatch out of the eggs after an
incubation period that varies with the individual
species. Maturation transitions through four
larval forms, resulting in the pupal form. The