Diseases, Conditions, Syndromes

Toxoplasmosis: Preventing mother-to-child transmission

Professor Maritza Jaramillo knows a thing or two about parasites—she has spent most of her life studying them. "During my bachelor's degree in Colombia, I did an internship at a lab specializing in parasitic infections. ...

Diseases, Conditions, Syndromes

How a South Indian script is changing the way science views parasite

Toxoplasma gondii is an insidious little parasite that infects one out of three people on the planet. A unique partnership between an engineer and a scientist produced data that challenged prevailing wisdom about this parasite's ...

Diseases, Conditions, Syndromes

Poverty as a disease trap

No drug can cure a paradox. That basic truth is at the heart of a new Stanford-led study highlighting how poverty traps make it impossible to eradicate a potentially deadly disease with current approaches.

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Parasitism

Parasitism is a type of symbiotic relationship between two different organisms where one organism, the parasite, takes favor from the host, sometimes for a prolonged time. In general, parasites are much smaller than their hosts, show a high degree of specialization for their mode of life, and reproduce more quickly and in greater numbers than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and diverse animals such as tapeworms, flukes, the Plasmodium species, and scabs. Parasitism is differentiated from parasitoidism, a relationship in which the host is always killed by the parasite such as moths, butterflies, ants, flies and others.

The harm and benefit in parasitic interactions concern the biological fitness of the organisms involved. Parasites reduce host fitness in many ways, ranging from general or specialized pathology (such as castration), impairment of secondary sex characteristics, to the modification of host behaviour. Parasites increase their fitness by exploiting hosts for food, habitat and dispersal.

Although the concept of parasitism applies unambiguously to many cases in nature, it is best considered part of a continuum of types of interactions between species, rather than an exclusive category. Particular interactions between species may satisfy some but not all parts of the definition. In many cases, it is difficult to demonstrate that the host is harmed. In others, there may be no apparent specialization on the part of the parasite, or the interaction between the organisms may be short-lived. In medicine, only eukaryotic organisms are considered parasites, with the exclusion of bacteria and viruses. Some branches of biology, however, regard members of these groups as parasitic.[citation needed]

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