Page 490 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 56 Nematodes

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mebooksfree.com mebooksfree.com Strongyloides stercoralis. Life cycle. Center and right side of figure describe the stages within the human (blue arrows). mebooksfree.com
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FIGURE 56–13
Filariform larvae penetrate the skin (step 1). Larvae migrate through lung and may cause pneumonia. Adult Strongyloides worms form in small
intestine. Eggs hatch in intestinal mucosa, and rhabditiform larvae are excreted in human feces, not worm eggs. Curved blue arrow ascending
from step 5 describes the autoinfection cycle in which filariform larvae form in the gastrointestinal tract and infect by penetrating the gut
mucosa or perianal skin. Left side of figure describes the maturation in the soil (red arrows). Note that steps 6, 7, and 8 constitute the free-living
life cycle in the soil. (Source: Dr. Alexander J. da Silva and Melanie Moser, Centers for Disease Control and Prevention.)

determine whether antibodies to Strongyloides are present
Important Properties
should be performed. If antibodies are found, the patient
The life cycle of T. spiralis is shown in Figure 56–14. Any
should be treated with ivermectin before immunosuppres-
mammal can be infected, but pigs are the most important
sion is undertaken, if possible.
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mebooksfree.com mebooksfree.com mebooksfree.com reservoirs of human disease in the United States (except in mebooksfree.com
Alaska, where bears constitute the main reservoir). Humans
TRICHINELLA
are infected by eating raw or undercooked meat contain-
ing larvae encysted in the muscle (see Figure 56–2K). The
Disease
larvae excyst and mature into adults within the mucosa of
Trichinella spiralis causes trichinosis. Trichinella spiralis is
the small intestine. Eggs hatch within the adult females,
also called the trichina worm.
and larvae are released and distributed via the bloodstream

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