Airless worms: A new hope against drug-resistant parasites

Over one billion people, including 880 million children, are infected with intestinal nematode worms, such as roundworms, hookworms and tapeworms, according to the World Health Organization. The infections are especially ...

Malaria hijacks your genes to invade your liver

In the search for new weapons against malaria, most drug development has focused on the parasites that cause the disease. But Duke University researchers are trying a different tack. Instead of targeting the malaria parasite ...

Climate warming could increase malaria risk in cooler regions

Malaria parasites develop faster in mosquitoes at lower temperatures than previously thought, according to researchers at Penn State and the University of Exeter. The findings suggest that even slight climate warming could ...

How an emerging tick-borne pathogen evades detection

Human babesiosis is an emerging infectious disease transmitted to humans by ticks. A team of Yale researchers has discovered how Babesia microti, one of the two Babesia parasite species that transmit the disease in the United ...

Parasites affect host responses to environmental change

Ignoring the role of parasites may lead to a misinterpretation of organism responses to environmental change, according to an Innovative Viewpoints article by ecologists from the University of Georgia. Their paper, "To improve ...

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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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