Where in the human body do parasites live?

Parasites can be found throughout the human body depending upon the parasite type. The three main classes of parasites that cause disease in humans include protozoa, ectoparasites and helminths.

A parasite gets its food at the expense of the host on which it is feeding. Protozoa are one-celled organisms that are able to multiply in human blood or tissue. Protozoa are classified into four groups: Sarcodina, Mastigophora, Ciliophora and Sporozoa.

Helminths are large organisms that are visible with the naked eye and include flatworms, thorny-headed worms and roundworms. The flatworms and thorny-headed worms are found in the gastrointestinal tract. Roundworms are found in the blood, gastrointestinal tract, lymphatic system or subcutaneous tissue. Ectoparasites are blood-sucking arthropods such as ticks, mites, mosquitoes and fleas.