[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 8 The Nematodes
207
these organisms are unable to complete their life
cycle, infecting the subcutaneous or skeletal
tissues. Human infection with either of these
organisms may produce a condition known as
cutaneous larva migrans. Characteristic symptoms
include skin lesions and intense itching,
which may lead to a secondary bacterial infection.
The lesions resemble creeping worms
through the skin. The treatment of choice is
thiabendazole; prevention of infection and
control of this accidental parasite may be accomplished
by avoidance of skin contact with dog
and cat feces.
Quick Quiz! 8-13
This adult hookworm is characterized by a buccal
cavity that contains teeth. (Objective 8-10A)
A. Ancylostoma
B. Necator
C. Both Ancylostoma and Necator
D. Neither Ancylostoma nor Necator
Strongyloides stercoralis
(stron”ji-loy’deez/stur”kor-ray’lis)
Common Name: Threadworm.
Common associated disease and condition
names: Strongyloidiasis, threadworm infection.
Morphology
Eggs. The eggs of Strongyloides stercoralis
have historically been considered indistinguishable
from those of hookworm (Fig. 8-18; Table
8-12). However, there are two features that when
present may help identify the eggs specifically.
First, the typical S. stercoralis egg measures only
slightly smaller than hookworm eggs, averaging
48 by 35 µm. Second, unlike hookworm, welldeveloped
larvae are almost always contained in
the S. stercoralis eggs. The eggs of both organisms
are similar in that when present, the two-,
Eight stage
embryonic cleavage
Quick Quiz! 8-14
Individuals contract hookworm via which of the following?
(Objective 8-6)
A. Contaminated water
B. Skin penetration
C. Insect bite
D. Contaminated food
Thin hyaline shell
Average size: 48 m by 35 m
FIGURE 8-18 Strongyloides stercoralis egg.
Quick Quiz! 8-15
Which of the following are appropriate Ascaris lumbricoides
prevention and control strategies? (Objective
8-8C)
A. Proper water treatment
B. Appropriate food handling
C. Use of insect repellent
D. Proper sanitation practices
TABLE 8-12
Parameter
Strongyloides stercoralis
Egg: Typical Characteristics
at a Glance
Description
Size Average, 48 by 35 µm
Typical growth phase Contains well-developed
larvae
Embryonic cleavage
Two-, four-, or eight-cell
stage, when present
Shell
Thin, hyaline