Page 484 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 56 Nematodes
473

A

B

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J
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K

H
FIGURE 56–2 A: Enterobius vermicularis female adult (6×). B: Trichuris trichiura female adult. Note the thin anterior (whiplike) end (6×). C: Ascaris
lumbricoides female adult (0.6×). D: Ancylostoma duodenale female adult (6×). E: Ancylostoma duodenale filariform larva (60×). F: Ancylostoma
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duodenale head with teeth (25×). G: Necator americanus head with cutting plates (25×). H: Strongyloides stercoralis female adult (60×). I: Strongyloides
stercoralis filariform larva (60×). J: Strongyloides stercoralis rhabditiform larva (60×). K: Trichinella spiralis cyst containing two larvae in muscle (60×).

Trichuris may also cause rectal prolapse in children
with heavy infection. Prolapse results from increased peri-
Albendazole is the drug of choice.
stalsis that occurs in an effort to expel the worms. The
whitish worms may be seen on the prolapsed mucosa.
Prevention
Epidemiology

Whipworm infection occurs worldwide, especially in the
ASCARIS
tropics; more than 500 million people are affected. In the Proper disposal of feces prevents transmission.
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Disease
United States, it occurs mainly in the southern states.
Ascaris lumbricoides causes ascariasis.
Laboratory Diagnosis
Diagnosis is based on finding the typical eggs (i.e., barrel-
The life cycle of A. lumbricoides is shown in Figure 56–6.
shaped [lemon-shaped] with a plug at each end) in the
stool (see Figures 56–3B and 56–5).
Humans are infected by ingesting worm eggs in food or

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A

D
C
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FIGURE 56–3
A: Enterobius vermicularis egg. B: Trichuris trichiura egg. C: Ascaris lumbricoides egg. D: Ancylostoma duodenale or Necator
americanus egg (300×). (Circles represent red blood cells.)

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