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Next Article What are the 12 colors? Occasionally found in feces, often found in tissue biopsies of infected individuals. Diagnostically found in feces of infected individuals.
The Parasite. Life Cycle. Animal Reservoirs. Clinical Presentation. Public Health Interventions. Glossary of terms. References and links. Excystation is the process by which the cyst is released upon receiving the ability to infect the host.
Excystation can release one or more cysts. For example, the trophozoite of Entamoeba histolytica , which causes Amoebiosis, first forms a single cyst. As the cyst matures, nuclear division produces four nuclei, and four uninucleate meta cystic amoeba appear during excystation. Cysts isolated from fecal samples have a protective wall, enabling the parasite to survive in the outside environment for a period ranging from days to a year, depending on the species and environmental conditions.
Some cysts show large secretory vesicles which secrete harmful chemicals upon excystation. Cysts are infectious particles and are involved in causing diseases to humans and other organisms where the causative agent is a protozoan. Some disease causing protozoans involved in cyst formation include:.
Trophozoite is the active, feeding, multiplying stage of most protozoa and is the dominant stage of the protozoan. In parasitic species, this stage is usually associated with pathogenesis. Trophozoites can be either flagellated on non-flagellated and termed using different terminology. Trophozoites of most protozoans are pear shapes with bilateral symmetry.
Trophozoite is nucleated with a central karyosome and median bodies. Fibrils run along the surface length of the parasite and are called axonemes. The function of the median bodies is not known, but most believe that they are somehow involved with the adhesive disk and its formation.
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