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Human parasites are divided into endoparasites, which cause infection inside the body, and ectoparasites, which cause infection superficially within the skin. The cysts and eggs of endoparasites may be found in feces , which aids in the detection of the parasite in the human host while also providing the means for the parasitic species to exit ...
When an intracellular parasite goes to enter a host cell, it is particular about the type of host cell. This is because most intracellular parasites are able to infect only a few different cell types. [21] Viruses use a number of host receptors to gain entry to the cell, usually by causing endocytosis. [7]
Parasite life cycles involving only one host are called "direct"; those with a definitive host (where the parasite reproduces sexually) and at least one intermediate host are called "indirect". [12] [13] An endoparasite lives inside the host's body; an ectoparasite lives outside, on the host's surface. [14]
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 ...
This parasite is multi-cellular, and capable of movement. They have numerous rear mucosal projections, which assumedly assist propulsion through the thin layer of skin on the inside of the human host's mouth. They also have an excretory system possessing lateral canals. This parasite eats epithelial cells.
Parasitoids have inspired science fiction authors and screenwriters to create terrifying parasitic alien species that kill their human hosts. [71] One of the best-known is the Xenomorph in Ridley Scott's 1979 film Alien, which runs rapidly through its lifecycle from violently entering a human host's mouth to bursting fatally from the host's chest.
Schistosoma mansoni is a water-borne parasite of humans, and belongs to the group of blood flukes (Schistosoma). The adult lives in the blood vessels (mesenteric veins) near the human intestine. It causes intestinal schistosomiasis (similar to S. japonicum, S. mekongi, S. guineensis, and S. intercalatum). Clinical symptoms are caused by the eggs.
Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including cryptosporidium, microsporidia, and isospora, are most common in HIV-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.