intracellular parasitism

biology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 29, 2026

Quick Summary

Intracellular parasitism occurs when one organism lives inside the body of another, unrelated organism. This relationship can be mutually beneficial or parasitic. In the context of disease, some microorganisms are obligate intracellular parasites, meaning they can only multiply within the cells of a host. Viruses, for example, lack conventional cell structures and are entirely dependent on host cells for replication, hijacking cellular processes to produce new virus particles. Protozoans like Trypanosoma cruzi and Leishmania also live inside host cells, such as macrophages, causing diseases like Chagas disease and leishmaniasis. This intimate relationship highlights the complex evolutionary dance between hosts and parasites.123

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

parasitism
…in the host’s body) or intracellular (inhabiting cells in the host’s body). Intracellular parasites—such as bacteria or viruses—often rely on a third organism, known as the carrier, or vector, to transmit them to the host. Malaria, which is caused by a protozoan of the genus Plasmodium transmitted to humans by…
Read More
…in the host’s body) or intracellular (inhabiting cells in the host’s body). Intracellular parasites—such as bacteria or viruses—often rely on a third organism, known as the carrier, or vector, to transmit them to the host. Malaria, which is caused by a protozoan of the genus Plasmodium transmitted to humans by…
Read More