It is not uncommon for humans to be hosts of parasites.
A parasitic relationship is a relationship between organisms in which one organism, the parasite, derives some benefit from the other organism, while the other organism, the parasite’s host, is harmed by the relationship. The parasite’s host is usually much larger than the parasite. Tapeworms, for example, are parasites that reside in the intestines of some vertebrates. Although they can get very long, their bodies usually remain small enough to fit in the host’s intestinal tract.
A parasitic infection can cause skin changes, such as a rash.
Parasites use their hosts for many different purposes. Most commonly, the parasite’s hosts are used as a food source for the parasite. They are also often used as a habitat for parasites. Hookworms, for example, reside in the intestinal tract of mammals such as dogs, cats, and humans. Finally, parasites use their hosts as a means of reproduction; Tapeworms and other parasites tend to reproduce in large numbers within their hosts.
Parasites can take up residence in the intestinal tract of dogs and cats.
In some parasitic relationships, larval development of the parasitic organism takes place in the body of the parasitic host. The parasites that do this are called parasitoids. In such situations, the parasite host is almost invariably killed. In many cases, the parasitoid also consumes the host.
There are many different parasitic relationships that a parasitic host can be in. In kleptoparasitism, the parasite steals food collected by the host. Brood parasites lay eggs in the nests of other organisms, which serve as surrogate parents and keep the eggs safe. Often, the parasite will remove one of the original eggs to make room for its own.
Tapeworms are parasites that reside in the intestines.
Generally speaking, only relationships between complex organisms can be considered parasitic relationships. For some purposes in biology, however, viruses are also considered parasites. Viruses attack and invade host cells, use them to reproduce, and spread to more cells, destroying the parasite’s host cell. Viruses, however, are generally not considered living organisms as they are not composed of cells.
Parasites can infect humans through an insect bite, as is the case with mosquito-borne diseases.
Parasitology is a branch of microbiology that deals with the relationships between parasites and their hosts. The field focuses on how parasites spread, what they gain from their hosts, and how they harm their hosts. Parasitologists often assist medical professionals in curing parasitic infections in humans.
It is not uncommon for a human to be a parasitic host. Parasites infect humans through insect bites, raw meat, contaminated vegetables, and dust containing parasitic larvae. Many different types of worms, such as flatworms and liver flukes, commonly infect humans. Many types of tiny protozoa can also reside in the human body.