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KEY CONCEPTS

KEY CONCEPTS

  • image Nitazoxanide and tinidazole are Food and Drug Administration (FDA)-approved for giardiasis treatment. While the FDA has not approved metronidazole for this indication, it has been widely accepted as the mainstay of giardiasis therapy for the past 50 years.

  • image Human immunodeficiency virus (HIV)-infected patients with cryptosporidiosis must receive antiretroviral therapy as the mainstay of therapy in addition to antiparasitic therapy.

  • image Serologic detection assays are required to diagnose Entamoeba histolytica infection because stool sample analysis is insensitive and does not distinguish between E. histolytica and the nonpathogenic E. dispar or E. moshkovskii.

  • image Metronidazole and tinidazole are tissue-acting agents against amoeba; whereas, paromomycin, iodoquinol, and diloxanide furoate are luminal amebicides.

  • image The drugs that have been used to treat Trypanosoma cruzi infections include benznidazole and nifurtimox, but are not currently approved by the FDA. Both are available from the Centers for Disease Control and Prevention (CDC) under an Investigational New Drug program.

  • image Chloroquine has been the recommended drug for malaria chemoprophylaxis, but clinicians have increasingly prescribed alternative antimalarial drugs such as atovaquone-proguanil, doxycycline, primaquine, and mefloquine because these regimens retain effectiveness in areas where chloroquine-resistant Plasmodium falciparum exposure is likely.

  • image Administration of corticosteroids or other immunosuppressive drugs to an infected individual can result in hyperinfections and disseminated strongyloidiasis.

  • image Antihelminthic therapy destroys parasites and may cause increased inflammation and worsening of neurocysticercosis symptoms.

  • image For head lice, the American Academy of Pediatrics recommends either nonprescription 1% permethrin or pyrethrins plus piperonyl butoxide topical preparations as agents of choice unless local resistance to these agents is documented.

  • image A single application of 5% permethrin results in cure rates in more than 90% of subjects with scabies at 14 and 28 days, but a second dose should be applied 1 week later because its ovicidal efficacy remains unclear.

Parasitic diseases remain a significant global health problem causing approximately one million deaths per year and affecting more than 1.7 billion people worldwide.1,2,3,4,5 In the United States, immunocompromised patients, ethnic/racial minorities, immigrants, those with recent travel to developing regions, individuals living in poor sanitary conditions, and people who lack access to basic health care services appear to be at highest risk for developing parasitic disease.6 However, people in every income and social strata can become infected. In fact, the Centers for Disease Control and Prevention (CDC) has referred to five diseases as neglected parasitic infections and has prioritized these for increased public health action.7 They include Chagas disease, cysticercosis, toxocariasis, toxoplasmosis, and trichomoniasis.8

This chapter discusses the major parasitic diseases including protozoan disease (giardiasis, cryptosporidiosis, Chagas disease, amebiasis, and malaria), helminthic infections (strongyloidiasis, cysticercosis, and toxocariasis), and ectoparasitic infestations (lice and scabies).

HOST–PARASITE RELATIONSHIP

Symbiosis is the association of two species for the purpose of obtaining food for either one or the other. Parasitism is a symbiotic relationship in which one species, ...

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