Antiparasitic Therapy

Parasitic infections remain a major cause of morbidity and mortality worldwide, particularly in impoverished tropical regions. It is helpful to group parasitic diseases and treatment into those caused by protozoa, single-celled organisms that multiply by cell division, and helminths, multicellular worms and flukes with complex internal structures. The most important protozoal diseases are attributable to members of the Apicomplexa that cause malaria, babesiosis, toxoplasmosis, and cryptosporidiosis and to the Kinetoplastida that are responsible for Chagas disease, human African trypanosomiasis (sleeping sickness), and leishmaniasis. Ameba and other types of protozoa also are important human pathogens. Helminths are subdivided into nematodes, or roundworms, which can be grouped into those that live in the gastrointestinal tract or elsewhere in the body, and platyhelminths, or flat worms, which are subdivided into cestodes, or tapeworms, and trematodes, or flukes. Depending on the helminth, albendazole, diethylcarbamazine, ivermectin, praziquantel, or another drug is used. Shortages of some antiparasitic drugs and substantial increases in the cost of others complicate therapy. Many antiparasitic drugs are commercially available in the United States; others can only be obtained from the Centers for Disease Control and Prevention Drug Service.