parasite, plant or animal that at some stage of its existence obtains its nourishment from another living organism called the host. Parasites may or may not harm the host, but they never benefit it. They include members of many plant and animal groups, and nearly all living things are at some time hosts to parasitic forms. Many bacteria are parasitic on external and internal body surfaces; some of these invade the inner tissues and cause disease (e.g., typhoid fever typhoid fever acute, generalized infection caused by Salmonella typhi. The main sources of infection are contaminated water or milk and, especially in urban communities, food handlers who are carriers.
..... Click the link for more information. , tuberculosis tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary,
..... Click the link for more information. , and some types of pneumonia). Parasitic plants cause great losses among food crops and trees (see diseases of plants diseases of plants. Most plant diseases are caused by fungi, bacteria, and viruses. Although the term disease is usually used only for the destruction of live plants, the action of dry rot and the rotting of harvested crops in storage or transport is similar
..... Click the link for more information. ). Parasites are more prevalent in the animal and protist kingdoms; most are invertebrates, chiefly worms, e.g., the fluke fluke, parasitic flatworm of the trematoda class, related to the tapeworm . Instead of the cilia, external sense organs, and epidermis of the free-living flatworms, adult flukes have sucking disks with which they cling to their hosts and an external cuticle that
..... Click the link for more information. , tapeworm tapeworm, name for the parasitic flatworms forming the class Cestoda. All tapeworms spend the adult phase of their lives as parasites in the gut of a vertebrate animal (called the primary host).
..... Click the link for more information. , and trichina (see trichinosis trichinosis (trĭk'ĭnō`sĭs) or trichiniasis
..... Click the link for more information. ); arthropods, e.g., the flea flea, common name for any of the small, wingless insects of the order Siphonaptera. The adults of both sexes eat only blood and are all external parasites of mammals and birds. Fleas have hard bodies flattened from side to side and piercing and sucking mouthparts.
..... Click the link for more information. and louse louse, common name for members of either of two distinct orders of wingless, parasitic, disease-carrying insects . Lice of both groups are small and flattened with short legs adapted for clinging to the host.
..... Click the link for more information. ; and protozoans. Among the protozoan protozoan (prō'təzō`ən), informal term for the unicellular heterotrophs of the kingdom Protista .
..... Click the link for more information. parasites that cause human disease are Amoeba (or Entamoeba) histolytica, the cause of amebic dysentery dysentery (dĭs`əntĕr'ē)
..... Click the link for more information. and liver abscess, and the several species of Plasmodium responsible for the three main types of malaria malaria, infectious parasitic disease that can be either acute or chronic and is frequently recurrent. Malaria is common in Africa, Central and South America, the Mediterranean countries, Asia, and many of the Pacific islands.
..... Click the link for more information. . Most parasites are obligate; i.e., they are unable to survive apart from their hosts. Often this is because in the course of evolution they have lost various of the organs necessary to live as independent units. Many parasites also have extremely specialized reproductive systems and complex life cycles, involving more than one host. Some higher plants and animals are parasitic, e.g., the dodders (vines of the morning glory family) and the cuckoo, which lays its eggs in the nests of other birds. Organisms that obtain their nourishment from dead organic matter are called saprophytes or saprobes, e.g., mushrooms. An epiphyte epiphyte (ĕp`əfīt') or air plant,
..... Click the link for more information. , or air plant, although it lives in association with another plant, is not a parasite. See also symbiosis symbiosis (sĭmbēō`sĭs), the habitual living together of organisms of different species.
..... Click the link for more information. .

parasite

Refers to software that is installed in your computer that you generally do not want and are not even aware of. There are many different types. Parasites can report your Web browsing habits to a marketing company over the Internet (spyware) or change your browser settings to point to a specific site. They can redirect searches to popular search engines to a site that sells a related product. They can cause you to dial up premium services.

Read the Small Print
Parasites are often installed with demos and freeware on the Web. Read the small print. Sometimes you can opt out of that extra utility that will be installed along with what you did want. Be sure your security settings are set to medium at least, and never click "Yes" to any dialog that asks "do you want to run" or "execute" something, unless you know what that something is! ActiveX controls on the Web can not only install parasites, but viruses as well.

Parasites often leave out an uninstall function and are not easily removed, although anti-parasite programs (spyware blockers) can detect and remove them. In addition, various Web sites have parasite detection scripts that analyze your computer and provide you with removal instructions (for example, visit www.doxdesk.com/parasite). See spyware.

parasite

an animal or plant that lives in or on another (the host) from which it obtains nourishment. The host does not benefit from the association and is often harmed by it

parasite [′par·ə‚sīt]

(biology)

An organism that lives in or on another organism of different species from which it derives nutrients and shelter.

(electricity)

Current in a circuit, due to some unintentional cause, such as inequalities of temperature or of composition; particularly troublesome in electrical measurements.

parasite (redirected from periodic parasite)

parasite

parasite
(redirected from periodic parasite)