Parasites live in other host organisms and depend on them for survival. Without a host, a parasite cannot live, grow, and multiply. For this reason, a parasite rarely kills its host, but it can spread diseases, some of which may be fatal.
Can parasites live outside a host?
Parasites that live outside the host are called ectoparasites (Figure 2A). For example, a flea is a parasite that lives on cats. In contrast, parasites that live inside their hosts are known as endoparasites (Figure 2B).
Can a parasite live independently?
Some are "facultative parasites," which are organisms that can become parasitic when the environmental conditions are right, but can also live independently. Many parasites have only one parasitic stage in their life cycle, or spend at least some portion of their life as free-living organisms.
Why can't parasites survive without host?
Most parasites cannot survive without their host, mainly because they have adapted to life on their host and they have lost some of the organs necessary for to live on their own.
How long can parasites live outside the body?
Giardiasis is a diarrheal disease caused by the microscopic parasite Giardia duodenalis (or “Giardia” for short). Once a person or animal has been infected with Giardia, the parasite lives in the intestines and is passed in stool (poop). Once outside the body, Giardia can sometimes survive for weeks or even months.
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