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PARASITIC INFECTIONS

The parasites that cause human disease represent a diverse, highly evolved, and complex group of organisms. Parasitic diseases are a major cause of global pediatric morbidity and mortality, with the heaviest disease burden occurring in low- and middle-income countries. Though less common in industrialized nations, parasites represent an important class of pathogens to recognize in this setting, as both endemic and imported cases are frequently encountered in pediatric practice. Given the complexity of this category of pathogens, a framework to organize human parasites according to their major biologic classification and predominant site (intestinal vs blood/tissue) of human interaction can be useful (Table 43–1). Additionally, understanding which organisms are associated with specific clinical presentations of parasitic diseases can help focus the diagnostic process (Table 43–2).

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Table 43–1. Framework for conceptualization of human parasitic infections and examples of representative organisms.
  Prominent Site of Involvement
Parasite Class Intestinal Tissue/Blood
Protozoa

Entamoeba

Giardia

Cryptosporidium

Malaria

Leishmania

Naegleria

Toxoplasma

Platyhelminthes (flatworms)

Cestodes

Taenia (ingested larvae)

Diphyllobothrium

Taenia/cysticercosis (ingested eggs)

Echinococcus

Trematodes (flukes)  

Schistosoma

Fasciola

Clonorchis

Nematodes (roundworms)

Ascaris

Hookworms

Strongyloides

Trichuris

Trichinella

Dracunculus

Angiostrongylus

Filaria

Table 43–2.Signs and symptoms of parasitic infection.

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