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Upon completion of the chapter, the reader will be able to:

  1. Identify the primary reasons why some parasitic diseases may be more prevalent in the US population.

  2. Describe the treatment algorithm for giardiasis and amebiasis.

  3. List one effective therapy for nematodes and select the drugs of choice for strongyloidiasis and tapeworms.

  4. List three major reasons why travelers are infected with malaria.

  5. Describe the presenting signs and symptoms of malaria.

  6. List some specific toxicities of mefloquine.

  7. Identify the monitoring parameters for quinidine gluconate in severe malaria.

  8. Define the major complications of falciparum malaria.

  9. Discuss the cardiovascular complications of chronic South American trypanosomiasis.

  10. Describe the steps to take to eradicate lice infestation and scabies.


Globalization, including international tourism, has lead to increases in the spread of various infectious diseases from endemic areas to areas new to these pathogens. Population shifts with refugees and new immigrant populations from other parts of the world have brought new parasitic infections to our shores. Migrant farm workers, the large and growing Central and South American immigrant population, and an increasing presence of immunosuppressed patients represent significant sources of parasitic infections in the United States.1–4

Parasitism is a relationship between organisms where one organism (the parasite) thrives at the expense of the host. Parasites have made metabolic and other defensive adaptations over time to increase their ability to survive host defenses and allow them to utilize the host’s biochemical systems to synthesize necessary cellular components.

Although acquired immunity to some parasitic diseases may lower the level of infection, absolute immunity as seen in viral and some bacterial infections is seldom seen in parasitic diseases. Since parasitic infections produce a wide variety of antigens because of the many life cycle phases, it is more difficult for the immune system to identify a constant antigen against which specific antibodies are protective.5 However, malaria remains a likely candidate for a vaccine and there are ongoing studies to develop one.6 Additionally, a vaccine for hookworms may advance to clinical trials based off initial animal studies.7

For more detailed discussions of parasites and the human parasites not discussed here, readers are directed to resources on parasites and parasitic diseases.8,9 Discussion in this chapter includes parasitic diseases more likely seen in the United States and includes gastrointestinal (GI) parasites (primarily giardiasis and amebiasis), protozoan infections (malaria and South American trypanosomiasis), some common helminthic diseases (specifically those caused by nematodes and cestodes), and ectoparasites (lice and scabies).


Epidemiology and Etiology

Giardia lamblia (also called G. intestinalis and G. duodenalis) is the most common intestinal parasite responsible for diarrheal syndromes throughout the world and is the most frequently identified intestinal parasite in the United States, with over 16,000 reported cases from 2011 to 2012.10 G. lamblia...

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