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Parasite Life Cycles (Part II)

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darodri6's version from 2016-03-14 18:53

Giardia Life Cycle

BeforeCurrentAfter
Human ingests CYSTS from contaminated food or water OR via Fecal:OralCYSTS (non-motile form) enter SI, and release TROPHOZOITES (motile form) via excystation (each cysts produces two trophozoites)Within the SI, the TROPHOZOITES multiply via binary fission
Within the SI, the TROPHOZOITES multiply via binary fissionafter replication, TROPHOZOITES can remain free-floating or attach to mucosal surface via sucking disksTROPHOZOITES then ENCYSTS again as they move towards the colon (cysts are very infectious) --> contaminate anything that comes into contact with it --> repeat cycle
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Trypanosoma Life Cycle (T. b. gambiense, T. b. rhodesiense)

BeforeCurrentAfter
Infected Tsetse fly (genus Glossina) inject metacyclic TRYPOMASTIGOTES into human skin tissue during a blood mealTRYPOMASTIGOTE enters lymphatic system --> enters bloodstreamOnce inside blood stream, becomes BLOODSTREAM TRYPOMASTIGOTE
Once inside blood stream, becomes BLOODSTREAM TRYPOMASTIGOTEuses bloodstream to access other body fluids (i.e. lymph, spinal fluid) and replicates via binary fission. ALWAYS EXTRACELLULAR!Tsetse fly (genus Glossina) becomes infected with BLOODSTREAM TRYPOMASTIGOTES during subsequent blood meal of infected host
Tsetse fly (genus Glossina) becomes infected with BLOODSTREAM TRYPOMASTIGOTES during subsequent blood meal of infected hostbloodstream Trypomastigotes reach fly's midgut --> transform into PROCYCLIC TRYPOMASTIGOTES & multiply via binary fissionPROCYCLIC TRYPOMASTIGOTES leave fly midgut --> transform into EPIMASTIGOTES
PROCYCLIC TRYPOMASTIGOTES leave fly midgut --> transform into EPIMASTIGOTESEPIMASTIGOTES reach fly's salivary glands and continue multiplication via binary fissionin the fly's salivary gland, EPIMASTIGOTES transform into METACYCLIC TRYPOMASTIGOTES again --> repeat cycle
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Trypanosoma Life Cycle (T. cruzi)

BeforeCurrentAfter
An infected triatomine insect (Rhodnius prolixus = "kissing" bug) (or Triatoma = "Assasin" bug) takes a blood meal on human host --> releases METACYCLIC TRPTOMASTIGOTES in its feces at wound siteMETACYCLIC TRYPTOMASTIGOTES enter host through wound OR through exposed mucosal membranes (i.e. conjunctiva)once inside the human host, TRYPTOMASTIGOTES invade cells near the site of inoculation--> differentiate into INTRACELLULAR AMASTIGOTES
once inside the human host, TRYPTOMASTIGOTES invade cells near the site of inoculation--> differentiate into INTRACELLULAR AMASTIGOTESAMASTIGOTES multiply via binary fission --> differentiate back into TRYPTOMASTIGOTESTRYPTOMASTIGOTES are then released into the circulation as BLOODSTREAM TRYPTOMASTIGOTES
TRYPTOMASTIGOTES are then released into the circulation as BLOODSTREAM TRYPTOMASTIGOTESBLOODSTREAM TYPTOMASTIGOTES travel to different tissues via bloodstream and transform back into AMASTIGOTES as they become intracellular in the new infection site and replicate via binary fission (replication ONLY occurs as amastigotes once they are intracellular!) --> cycle between blood tryptomastigotes and intracellular amastigotes repeats over and over"kissing" bug becomes infected when it takes a blood meal on an infected human host and the BLOODSTREAM TRYPTOMASTIGOTE enters kissing bug
"kissing" bug becomes infected when it takes a blood meal on an infected human host and the BLOODSTREAM TRYPTOMASTIGOTE enters kissing bugThe ingested TRYPTOMATIGOTES transform into EPIMASTIGOTE once inside the kissing bug's midgut and multiplyafter EPIMASTIGOTES within kissing bug's gut multiply, they differentiate into infectious METACYCLIC TRYPTOMASTIGOTES in the hindgut until Triatomine (kissing bug) takes another blood meal on human host --> repeat cycle
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Toxoplasma Life Cycle (T. ghondi)

BeforeCurrentAfter
Unsporulated oocysts are shed in cat's feces (definitive host)Oocysts sporulate in next few days in the environment (soil/water/plants) --> become infectiveIntermediate host (i.e. birds, rodents) ingest oocyst-contaminated soil/water/plant and become infected
Intermediate host (i.e. birds, rodents) ingest oocyst-contaminated soil/water/plant and become infectedAfter ingestion by birds/rodents, oocysts transform into TACHYZOITESTACHYZOITES localize in neural and muscle tissue and develop into tissue cyst BRADYZOITES
TACHYZOITES localize in neural and muscle tissue and develop into tissue cyst BRADYZOITESCats become infected after consuming intermediate host harbouring tissue cysts (BRADYZOITES) OR via consumption of sporulated oocyst within the soil/water/plants
Humans can also be infected via ingestion of undercooked, intermediate hosts (i.e. pigs, goats, etc) containing tissue cysts (BRADYZOITES), ingestion of contaminated food/water or via fecal-contaminated soil/changing litter box.
Pregnant humans can pass along to fetus!!!!
In humans (accidental host), parasite forms tissue cysts within skeletal, brain and eye tissue

In cats, BRADYZOITES enter intestinal epithelial cells and transform into TROPHOZOITES
In cats, BRADYZOITES enter intestinal epithelial cells and transform into TROPHOZOITESTROPHOZOITES undergo schizogeny to make merozoites (merogony; asexual reproduction) --> MEROZOITES become GAMETOCYTES (gametogony; asexual reproduction) --> micro & macrogametocytes form zygotes (sexual repro) --> ZYGOTES become cystsunsporulated oocysts from zygotes (containing 2 sporocysts) are shed in cat's feces --> repeat cycle
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Plasmodium Life Cycle (P. vivax, ovale, falciparum, malariae)

BeforeCurrentAfter
Malaria-infected female mosquito (Anopheles) injects SPOROZOITES into the human host during a blood mealSPOROZOITES infect liver cells and mature into SCHIZONTSSCHIZONTS rupture and release MEROZOITES = END of Exo-Erythrocytic Phase (P. vivax & P. ovale can also form HYPNOZOITES and remaine dormant in liver/evade immune system)
SCHIZONTS rupture and release MEROZOITES = END of Exo-Erythrocytic Schizogony Phase (P. vivax & P. ovale can also form HYPNOZOITES and remaine dormant in liver/evade immune system)released MEROZOITES then undergo asexual multiplication in the erythrocytes = BEGIN Erythrocytic Cycle/Schizogony --> merozoites infect RBCs -->repeat cycle of reinfecting more RBCs and replicating. Lead to "paroxsyms" due to schizont release of merozoites (toxins) at various intervals, which induce fever/chillsRing stage TROPHOZOITES mature into SCHIZONTS, which rupture and release more MEOROZOITES
Ring stage TROPHOZOITES mature into SCHIZONTS, which rupture and release more MEOROZOITESsome parasites differentiate into sexual erythrocytic stage (GAMETOCYTES)GAMETOCYTES (male = micro & female = macro) are ingested during subsequent blood meal by Anopheles mosquito = End Erythrocytic Cycle
GAMETOCYTES (male = micro & female = macro) are ingested during subsequent blood meal by Anopheles mosquito = End Erythrocytic Cycle --> Begin Sporogonic CycleWhile in the mosquito's gut, the microgametes penetrate the macrogametes and make ZYGOTES (sexual repro)ZYGOTE then becomes motile and elongated (ookinetes), which allows them to invade mosquito's gut wall and develop into OOCYSTS (sporogony)
ZYGOTE then becomes motile and elongated (ookinetes), which allows them to invade mosquito's gut wall and develop into OOCYSTS (sporogony)OOCYTS within mosquito gut wall grow, rupture and release SPOROZOITESSPOROZOITES make their way to mosquito's salivary gland --> mosquito bites another host and injects sporozoites --> repeat cycle
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