Acanthamoeba castellanii

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Acanthamoeba castellanii is an opportunistic protozoan parasite. This free-living ubiquitous parasite mainly founds in freshwater sources like lakes, swimming pools, tap water, and contact lens solutions, heating and air conditioning units, soil, sea water, sewage. Its lifecycle constists of two uninucleate stages, one is motile trophozoite and other is dormant cyst. Flagellated stage is absent in A. Castellanii. These trophozoites feed upon Gram-negative bacteria in nature and reproduce by binary fusion.


Cryptosporidium parvum

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Cryptosporidium is a rare, opportunistic animal pathogen and C. parvum causes infection in humans. Asexual reproduction is common in these species and they form main infectious agent 'oocysts' by the sexual reproduction.These oocyst releases four sporozoites that are motile in nature, complete their entire biological cycle in single host and come out with the stool. These pathogens are ubiquitous and transmitted to man in various ways: man-to-man, animal-to-man, or from contaminated water, food or air. It can survive most environments for long periods of time due to its "hardy cyst".


Cyclospora cayetanensis

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C. cayetanensis is a unicellular coccidian parasite of humans. It causes disease into people who travels different areas, indigenous people of developing countries, children and immunocomprised persons. It is found in both food and water sources. It infects upper intestine and causes protracted diarrhea in people. The non-sporulated oocysts, excreted by infected person in their feces are not infectious but after one week they start sporulation and become infectious. C. cayetanensis can complete its full life cycle in one host.


Entamoeba histolytica

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E. histolytica is a non-flagillated only protozoan that infects into the human intestines. It transmits one person to another person by ingesting the feacally contaminated water, food, surface contact. It enters in human body in form of non-infectious cysts. If these cysts survive into acidic stomach they tranform theirselves to trophozoites. Trophozoites are the infectious stage and mainly attacks on human large intestine where it starts distroying tissue and causes internal inflamation and other diseases. Then it encyst and exit from the body with the feces.


Giardia lamblia

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G. lamblia, also known as G. Intestinalis is a intestinal flagellated water pathogen. It is a ubiquitous parasite that found in fresh water sources like lakes, ponds, tap water, pools, wells and soil and food contaminated with infectious feces. It completes its life cycle into two stages: one is infectious motile trophozoite stage (into intestine) and other one is non-infective cyst stage that is responsible for transmission. These trophozoites get their nutrition from intestinal walls in form of carbohydrates. These cysts can also be transmitted by anal-oral sexual intercourse.


Naegleria fowleri

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Naegleria fowleri is a free-living, flagellated, thermophilic protzoan parasite in humans. It is also known as 'brain-eating amoeba parasite' because it travels up the nose to brain via olfactory nerves where it causes several damages in CNS and most of the infected people die within a week. It is mostly found in water sources which have iron or iron-containing compounds which favor growth of this parasite. Besides it, N. fowleri can also be isolated from indoor swimming pools, domestic water supplies sources and soil. It completes its life cycle in three stages, trophozoite stage (infectious stage), flagellate stage (temporary, non-feeding transformtion in unfavorable conditions) and cyst stage (non-infectious).


Toxoplasma gondii

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T. gondii is an obligate intracellular parasite. It has three stages in its life cycle: the tachyzoite, tissue cyst (bradyzoites) and oocysts. All forms are necessary to maintain the organism in the host. It shows both sexual and asexual reproduction, depends on the host. Life cycle of T. gondii in mammals starts with ingestion of tissue cysts or ocysts via infected fecal contaminated water or uncooked meat. The enzymes of digestive system of mammals disrupt the cyst wall and release many viable organisms (tachyzoites) into the digestive tract and penetrate the gastrointestinal mucosa and disseminate widely throughout the body.