Any organism living in or on another living creature and deriving advantage from it, while causing the host disadvantage. The parasite obtains food from the host’s blood, tissues, or diet. Parasites may spend only part of their life-cycles with the host or remain there permanently. Some parasites cause few symptoms, while others cause disease or even death.
Animal parasites of humans include protozoa, worms, flukes, leeches, lice, ticks, and mites. Viruses and diseasecausing fungi and bacteria are also essentially parasites.
A plant or animal which lives upon or within or upon another living organism at whose expense it obtains some advantage without compensation. By convention, human parasitology covers the study of the protozoa, helminths and arthropods infecting humans.
An organism which lives in or on another organism, known as the host. A parasite derives all its nourishment from the host but provides no bene?ts in return. It may damage the host’s bodily functions and in extreme cases cause the death of the host. Human parasites include WORMS, fungi (see FUNGUS), BACTERIA and viruses (see VIRUS).
n. any living thing that lives in (see endoparasite) or on (see ectoparasite) another living organism (see host). The parasite, which may spend all or only part of its existence with the host, obtains food and/or shelter from the host and contributes nothing to its welfare. Some parasites cause irritation and interfere with bodily functions; others destroy host tissues and release toxins into the body, thus injuring health and causing disease. Human parasites include fungi, bacteria, viruses, protozoa, and worms. See also commensal; symbiosis. —parasitic adj.
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