Malaria risk is highest in early evening, study finds

Wide-scale use of insecticide-treated bed nets has led to substantial declines in global incidences of malaria in recent years. As a result, mosquitos have been shifting their biting times to earlier in the evening and later ...

Map of malaria behavior set to revolutionize research

The first detailed map of individual malaria parasite behaviour across each stage of its complicated life cycle has been created by scientists. Researchers at the Wellcome Sanger Institute and their collaborators used advanced ...

Parasitic plants use stolen genes to make them better parasites

Some parasitic plants steal genetic material from their host plants and use the stolen genes to more effectively siphon off the host's nutrients. A new study led by researchers at Penn State and Virginia Tech reveals that ...

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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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