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Most bacteria and viruses undergo passive uptake, where they rely on the host cell for uptake. However, apicomplexans engage in active entry. [ 8 ] One obligate wasp parasite, Polistes atrimandibularis , infiltrates its hosts' colony by modifying its chemical signature to match that of the hosts. [ 9 ]
Obligate intracellular parasites cannot reproduce outside their host cell, meaning that the parasite's reproduction is entirely reliant on intracellular resources. All viruses are obligate intracellular parasites. Bacterial examples (that affect humans) include: Chlamydia, and closely related species. [14] Rickettsia; Coxiella
This is an accepted version of this page This is the latest accepted revision, reviewed on 19 January 2025. Relationship between species where one organism lives on or in another organism, causing it harm "Parasite" redirects here. For other uses, see Parasite (disambiguation). A fish parasite, the isopod Cymothoa exigua, replacing the tongue of a Lithognathus Parasitism is a close ...
As bacterial and viral infections can both cause the same kinds of symptoms, it can be difficult to distinguish which is the cause of a specific infection. [11] Distinguishing the two is important, since viral infections cannot be cured by antibiotics whereas bacterial infections can.
An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available.These opportunities can stem from a variety of sources, such as a weakened immune system (as can occur in acquired immunodeficiency syndrome or when being treated with immunosuppressive drugs, as in cancer treatment), [1] an altered ...
Viruses, however, use a completely different mechanism to cause disease. Upon entry into the host, they can do one of two things. Many times, viral pathogens enter the lytic cycle; this is when the virus inserts its DNA or RNA into the host cell, replicates, and eventually causes the cell to lyse, releasing more viruses into the environment.
Although organisms such as bacteria function as parasites, the usage of the term "parasitic disease" is usually more restricted. The three main types of organisms causing these conditions are protozoa (causing protozoan infection), helminths (helminthiasis), and ectoparasites. [5]
Tissue tropism is the range of cells and tissues of a host that support growth of a particular pathogen, such as a virus, bacterium or parasite. [1] [2] Some bacteria and viruses have a broad tissue tropism and can infect many types of cells and tissues. [1] Other viruses may infect primarily a single tissue. [1]