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Parasites are organisms that derive their sustenance from other organisms, live in or on other organisms, and obtain their sustenance at the host’s expense. Human disease may be caused by three types of parasites: ectoparasites, helminths, and protozoa. The burden of disease is greatest in developing countries, particularly in tropical and subtropical regions, but people in industrialized countries may also be infected with parasites. Often parasites are transmitted through the consumption of unclean food or water, but they can also be spread through blood or other means, including transmission from animals to humans. Antiparasitic drugs combat parasites and the diseases they cause, and a wide variety of antiparasitic drugs are available today to combat specific diseases. However, some drugs are no longer effective due to ...

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