[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 13 The Arthropods
Epidemiology and Geography
Scorpions can be found throughout the world,
except for New Zealand and Antarctica, but are
more prevalent in tropical and subtropical climates.
Many species are found in the United
States, primarily in the southern and western
states. They are most common in the desert
Southwest. Two species are of medical concern
because their venom can have potentially lethal
effects—Hadrurus spp. (desert hairy scorpion)
and Centruroides spp. (bark scorpion).
Clinical Symptoms
The venom of scorpions is classified as a neurotoxin,
which is used to paralyzes its prey. In
addition to symptoms associated directly with
the action of the toxin, some individuals may
display an allergic reaction to the venom, which
could lead to anaphylaxis and death. Most scorpions
are not able to inject enough venom to kill
a healthy adult human, but older adults, very
young children and infants, and those who are
immunocompromised are at risk. The sting site
will become painful and swollen; there may be
a tingling or numbing sensation. In the most
severe cases, hypertension, pulmonary edema,
and cardiac arrhythmia may result.
Treatment
Most hospital emergency rooms in desert cities
in the Southwest (e.g., Phoenix, Tucson, Las
Vegas) carry scorpion antivenin, which can treat
at-risk patients or those displaying an intense
systemic reaction. Supportive therapy, pain management,
and medication to control anaphylaxis
may also be needed.
Prevention and Control
Similar to prevention and control measures for
spiders, prevention of a human scorpion sting is
a matter of minimizing places where they can
hide and breed. Pesticides can be used around
dwellings but are not always effective. Sealing
holes in exterior walls where plumbing pipes and
electrical wires enter a home is essential for preventing
their access to inside living spaces.
Quick Quiz! 13-13
Unlike the other arachnids discussed in this chapter,
scorpions are equipped with a designated pair of
clawlike legs used to hold their prey. (Objective 13-5)
A. True
B. False
C. Unable to determine
Quick Quiz! 13-14
With each molting, developing scorpions change
morphologically and increase in size. (Objective 13-6)
A. True
B. False
C. Unable to determine
Quick Quiz! 13-15
Healthy individuals are at the greatest risk of developing
serious complications following the bite of a
scorpion. (Objective 13-9)
A. True
B. False
C. Unable to determine
Fleas
Morphology
Fleas range in size from 1.3 to 4 mm (Fig. 13-8;
Table 13-5). Fleas are equipped with three pairs
of powerful hairy legs and clawlike feet. These
features, plus the fact that the rear pair of legs is
extra long, allow fleas to move about quickly by
jumping. Their compact segmented bodies enable
them to migrate through the feathers or hairs of
their hosts. The mouth parts of fleas are designed
for piercing and blood sucking. The presence or
absence of eyes, comblike structures located above
the mouth parts (called genal ctenidia), and