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If a parasite has to infect a given host in order to complete its life cycle, then it is said to be an '''''obligate''''' parasite of that host; sometimes, infection is '''''facultative'''''—the parasite can survive and complete its life cycle without infecting that particular host species. Parasites sometimes infect hosts in which they cannot complete their life cycles; these are '''''accidental''''' hosts. |
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If a parasite has to infect a given host in order to complete its life cycle, then it is said to be an '''''obligate''''' parasite of that host; sometimes, infection is '''''facultative'''''—the parasite can survive and complete its life cycle without infecting that particular host species. Parasites sometimes infect hosts in which they cannot complete their life cycles; these are '''''accidental''''' hosts. |
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A host in which parasites have sexual reproduction is known as the '''''definitive''''', '''''final''''' or '''''primary''''' host. In '''''intermediate''''' hosts, parasites either do not reproduce or do so asexually, but the parasite always develops to a new stage in this type of host. In some cases a parasite will infect a host, but not undergo any development, these hosts are known as '''paratenic'''<ref>Schmidt and Roberts. 1985. Foundations of Parasitology 3rd Ed. Times Mirror/Mosby College Publishing</ref> or '''transport''' hosts. The paratenic host can be useful in raising the chance that the parasite will be transmitted to the definitive host. For example the cat lungworm (''Aelurostrongylus abstrusus'') uses a slug or snail as an intermediate host; the first stage larva enters the mollusk and develops to the third stage larva, which is infectious to the definitive host—the cat. If a mouse eats the slug, the third stage larva will enter the mouse's tissues, but will not undergo any development. |
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A host in which parasites have sexual reproduction is known as the '''''definitive''''', '''''final''''' or '''''primary''''' host. In '''''intermediate''''' hosts, parasites either do not reproduce or do so asexually, but the parasite always develops to a new stage in this type of host and then they will have many babies and kill the host and move on to another host and do the same thing. In some cases a parasite will infect a host, but not undergo any development, these hosts are known as '''paratenic'''<ref>Schmidt and Roberts. 1985. Foundations of Parasitology 3rd Ed. Times Mirror/Mosby College Publishing</ref> or '''transport''' hosts. The paratenic host can be useful in raising the chance that the parasite will be transmitted to the definitive host. For example the cat lungworm (''Aelurostrongylus abstrusus'') uses a slug or snail as an intermediate host; the first stage larva enters the mollusk and develops to the third stage larva, which is infectious to the definitive host—the cat. If a mouse eats the slug, the third stage larva will enter the mouse's tissues, but will not undergo any development. |