Page 475 - Review of Medical Microbiology and Immunology ( PDFDrive )

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464
PART VI Parasitology

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arrows). (Source: Dr. Alexander J. da Silva and Melanie Moser, Centers for Disease Control and Prevention.) mebooksfree.com

FIGURE 55–1
Schistosoma species. Life cycle. Right side of figure describes the stages within the human (blue arrows). Humans are
infected at step 2 when free-swimming cercariae penetrate human skin. Cercariae differentiate into adult worms (two sexes) that migrate to the
mesenteric veins (Schistosoma mansoni and Schistosoma japonicum) or the venous plexus of the urinary bladder (Schistosoma haematobium).
The adult worms lay eggs, which appear in the stool (S. mansoni and S. japonicum) or the urine (S. haematobium). The eggs pass into fresh water,
where the miracidia stage infects snails, which produce cercariae. Left side of figure describes the stages in fresh water and in the snail (red

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Clinical Findings
Eosinophilia is seen in response to the migrating larvae.
Most patients are asymptomatic, but chronic infections
This stage usually resolves spontaneously.
may become symptomatic. The acute stage, which begins
The chronic stage can cause significant morbidity and
shortly after cercarial penetration, consists of itching and
mortality. In patients with S. mansoni or S. japonicum
dermatitis followed 2 to 3 weeks later by fever, chills,
infection, gastrointestinal hemorrhage, hepatomegaly, and

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