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Definitive or primary host – an organism in which the parasite reaches the adult stage and reproduces sexually, if possible. This is the final host. Secondary or intermediate host – an organism that harbors the sexually immature parasite and is required by the parasite to undergo development and complete its life cycle. It often acts as a ...
Parasitism is a major aspect of evolutionary ecology; for example, almost all free-living animals are host to at least one species of parasite. Vertebrates, the best-studied group, are hosts to between 75,000 and 300,000 species of helminths and an uncounted number of parasitic microorganisms.
These can be categorized into three groups; cestodes, nematodes and trematodes.Examples include: Acanthocephala; Ascariasis (roundworms); Cestoda (tapeworms) including: Taenia saginata (human beef tapeworm), Taenia solium (human pork tapeworm), Diphyllobothrium latum (fish tapeworm) and Echinococcosis (hydatid tapeworm)
Main article: Human parasite Endoparasites Protozoan organisms Common name of organism or disease Latin name (sorted) Body parts affected Diagnostic specimen Prevalence Source/Transmission (Reservoir/Vector) Granulomatous amoebic encephalitis and Acanthamoeba keratitis (eye infection) Acanthamoeba spp. eye, brain, skin culture worldwide contact lenses cleaned with contaminated tap water ...
Parasites can provide information about host population ecology. In fisheries biology, for example, parasite communities can be used to distinguish distinct populations of the same fish species co-inhabiting a region. Additionally, parasites possess a variety of specialized traits and life-history strategies that enable them to colonize hosts.
Bird parasites mitigate the risk of egg loss by distributing eggs amongst a number of different hosts. [9] As such behaviours damage the host, they often result in an evolutionary arms race between parasite and host as they coevolve. [10] [11] Some host species have strong rejection defenses, forcing the parasitic species to evolve excellent ...
Therefore, the parasites are transmitted directly into the host's blood stream. Pool feeders such as the sand fly and black fly, vectors for pathogens causing leishmaniasis and onchocerciasis respectively, will chew a well in the host's skin, forming a small pool of blood from which they feed.
The parasite may live outside of the host ectoparasite; for example, a tick. Alternatively, the parasite may live within the host endoparasite ; for example, the fluke . An obligate parasite that does not live directly in or on the host, but rather acts at a distance – for example, a cuckoo which hatches and is raised by non-relatives – is ...