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Parasite Life Cycles (part I - Worms)

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darodri6's version from 2016-03-15 18:38

Nematode Life Cycle (Ascaris lumbricoides)

BeforeCurrentAfter
Adult worm lives in the lumen of HUMAN small intestineFemale adult worm within human SI produces thousands of EGGS dailyEggs released by female in the SI are passed in human feces
Eggs released by female in the SI are passed in human fecesegg must be fertilized under proper conditions (good moisture & temp within SOIL).....if not fertilized = not infectiousFertilized (infectious) eggs are swallowed by humans via contaminaed VEGETABLES (mainly) --> LARVAE hatch from egg
Fertilized (infectious) eggs are swallowed by humans --> larvae hatch from eggLarvae inside intestinal mucosa of human --> enter PORTAL, then SYSTEMIC, circulationonce inside systemic circulation, LARVAE MATURE in LUNGS --> penetrate alveolar walls --> ascend bronchial tree to the throat --> re-swallowed
once inside systemic circulation, larvae mature in lungs --> penetrate alveolar walls --> ascend bronchial truee to the throat --> re-swallowedonce mature larvae re-enter the SI, develop into ADULT WORMS (remain in SI via continuous movement; NO attachment)Adult worms live within the SI, and females will release thousands of EGGS daily --> repeat cycle
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Nematode Life Cycle (Wuchereria Bancrofti)

BeforeCurrentAfter
Infected mosquito (Culex or Anopheles) place 3rd-stage FILARIAL LARVAE onto skin of human host3rd-stage FILARIAL LARVAE penetrate into the mosquito bite location --> enter blood stream3rd stage FILARIAL LARVAE develop into adults and reside in human lymphatics
3rd stage FILARIAL LARVAE develop into adults and reside in human lymphaticsonce in lymphatics of human, adults produce MICROFILARIAEMICROFILARIAE migrate throughout the lymphatic and bloodstream channels
MICROFILARIAE migrate throughout the lymphatic and bloodstream channelsA mosquito that subsequently bites the human host, ingests the MICROFILARIAE during its blood mealOnce inside the mosquito's gut, the MICROFILARIAE work their way into the proventriculus and cardiac portion of the mosquitos midgut --> reach THORACIC MUSCLES
Once inside the mosquito's gut, the MICROFILARIAE work their way into the proventriculus and cardiac portion of the mosquitos midgut --> reach THORACIC MUSCLESOnce in the thoracic muscles of the mosquito, MICROFILARIAE develop into 1st-stage larvae --> 3rd stage infective FILARIAL LARVAE3rd-stage infective FILARIAL LARVAE migrate to to mosquito's proboscis (long mouthpart) --> injected into human host during mosquito's next blood meal --> repeat cycle
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Nematode Life Cycle (Trichninella spiralis)

BeforeCurrentAfter
Human ingests raw/undercooked meat infected with ENCYSTED LARVAE (usually from pigs or wild game)once in the human gut, cysts release the LARVAE (due to burst from gastric acid)newly released LARVAE invade SI mucosa by invading several microvilli (i.e. intramulticellular) and develop into ADULT WORMS
newly released LARVAE invade SI mucosa by invading several microvilli (i.e. intramulticellular) and develop into ADULT WORMSFemale worms within the SI release new LARVAE that contain a STYLET to penerate SI wall and enter blood/lymphatic vessel = END of ENTERO (asymptomatic) PHASE -->BEGIN PARANTERAL PHASEnew LARVAE released from female adult worm migrate to striated muscle (via use of their esophageal stylet) and enter skeletal muscle. LARVAE become ENCYSTED and are nurtured by a muscle 'Nurse' cell (fed/waste removed) (Ingestion of more encysted larvae continues the process, but it is NOT CYCLICAL!
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Trematodes Life Cycle

BeforeCurrentNext
Eggs eliminated in human feces or urine (into the water)MIRACIDIA are released and swim to and penetrate SNAIL (intermediate host)2 generations of SPOROCYSTS are formed --> rediae
2 generations of sporocysts are formed --> rediaeCERCARIAE are produced and released and swim to and penetrate (infect) HUMAN hostsCERCARIAE forked tail is shed
cercariae forked tail is shedbecome SCHISTOSOMULAEmigrate through several tissues and stages to their residence in the veins --> carried to LUNGS and/or LIVER to mature into adults
migrate through several tissues and stages to their residence in the veins --> carried to LUNGS and/or LIVER to mature into adultseventually make their way to the superior MESENTERIC VEIN systemS. mansoni & S. japonicum reside in mesenteric venules of BOWEL/RECTUM
& S. haematobium reside in venous plexous of BLADDER
S. mansoni & S. japonicum reside in mesenteric venules of bowel/rectum
& S. haematobium reside in venous plexous of bladder
EGGS are depositied by the females into the small venules of the portal and perivesical systemsEGGS are moved progressively towards the lumen of the intestine (s. japonicum/mansoni) and of the bladder and ureters (s. haematobium) and are eliminated in feces/urine (into the water) -->repeat cycle
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Cestodes Life Cycle (Taenia saginata & T. solium)

BeforeCurrentNext
EGGS from GRAVID PROGLOTTIS passed in HUMAN feces --> contaminated water (eggs can live for a while in this water)Cattle (T. saginata) and/or pigs (T. solium) become infected after eating vegatation that was irrigated with contaminated water containing eggs (from gravid proglottids) in human fecesONCOSPHERES hatch within pig/cattle's intestines
ONCOSPHERES hatch within pig/cattle's intestinesONCOSPHERES invade intestinal wall, and migrate to the STRIATED MUSCLESonce in striated muscles of pigs/cattle, develop into CYSTICERCI (can survive for several years here)
once in striated muscles of pigs/cattle, develop into CYSTICERCI (can survive for several years here)humans ingest raw/undercooked infected cattle or pig (containing CYSTICERCI in their striated muscle)once inside human intestine, CYSTICERCI develops into ADULT TAPEWORM over next few months (can survive for years here)
once inside human intestine, CYSTICERCI develops into adult tapeworm over next few months (can survive for years here)tapeworms inside human intestine attach to small intestine via their SCOLEX and reside in the small intestineadult tapeworms within human small intestine produce PROGLOTTIDS (immature eggs), which become mature eggs (aka GRAVID PROGLOTTIDS), which detach from tapeworm and are passed in human feces
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Cestodes Life Cycle (Echinococcus granulosa)

BeforeCurrentNext
E. granulosis resides in small bowel of dogs (definitive host)EGGS released from GRAVID PROGLOTTIDS --> passed in dogs fecesEGGS in dog feces ingested by intermediate host (sheep, goat, cattle, horse, etc)....human can also become intermediate host via accidental ingestion of egg-contaminated feces
once inside intermediate host, egg hatches in the small bowel and releases ONCOSPHERESeggs hatch within intermediate host (i.e. sheep, human, etc.) --> release ONCOSPHERES --> penetrate the intestinal wall of intermediate host and migrates via circulatory system into various organs (esp. LIVER, lungs, brain, eyes --> "HYATID CYST")once ONCOSPHERE is inside various organs (esp. LIVER, lungs, brain, eyes), it develops into a CYST that enlarges gradually
once ONCOSPHERE is inside various organs (esp. Liver & lungs), it devlops into a CYST that enlarges graduallyenlarged CYSTS inside of lungs/liver produce PROTOSCOLICES (aka hyatid sand) & daughter cells that fill the cyst interiordefinitive host (DOG) becomes infected via eating CYST-infected organs of the intermediate hosts (i.e. sheep, goats, etc.)
definitive host (dog) becomes infected via eating CYST-infected organs of the intermediate hosts (i.e. sheep, goats, etc.)after ingestion of contmainated organs by definitive host (dog), PROTOSCOLICES (aka hyatid sand) within the ingested CYST are released --> attach to intestinal mucosaPROTOSCOLICES from the lysed cyst develop into adult stage within the dog's small bowel --> matures into adult tapeworm (E. granulosis) -->repeat cycle
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Cestodes Life Cycle (Diphyllobothrium Latum)

BeforeCurrentNext
Immature eggs (NOT PROGLOTTIDS) passed in human feces --> reach water resourceseggs in human feces-contaminated water yield ONCOSPHERESONCOSPHERES develop into CORACIDIA that live in the fresh water
ONCOSPHERES develop into CORACIDIA that live in the fresh waterCORACIDIA ingested by copepod crustacean (first intermediate host) and develops into PROCEROIDPROCEROID-containing crustacean is ingested by a small fish (usually minnows, etc.; second intermediate host) OR human drinks water containing the infected crustaceans --> proceroids invade intestinal wall of human, rest in muscle, and grow into PLEROCEROIDS => Sparagnosis infection
NOTE: (rest of life cycle focused on food-ingestion route, not water-consumption route)
PROCEROID-containing crustacean is ingested by a small fish (usually minnows, etc.; second intermediate host) OR human drinks water containing the infected crustaceans --> proceroids invade intestinal wall of human, rest in muscle, and grow into PLEROCEROIDS.
NOTE: (rest of life cycle focused on food-ingestion route, not water-consumption route)
Once inside the small fish, the PROCEROID larvae are released and migrate to the fish fleshonce within flesh of small fish, proceroid develop into PLEROCEROID (aka sparagnum) larvae within the small fish (infective stage for humans, but normally not an issue b/c we normally eat larger fish only)
once within flesh of small fish, proceroid develop into PLEROCEROID (aka sparagnum) larvae within the small fish (infective stage for humans, but normally not an issue b/c we normally eat larger fish only)Small fish (containing PLEROCEROID within their flesh) are eaten by larger fish (i.e. trout, perch, etc.)Once inside the larger fish, the PLEROCEROID (aka sparagnum) migrate to muscles of large fish
Once inside the larger fish, the PLEROCEROID (aka sparagnum) migrate to muscles of large fishHumans acquire disease via eating larger fish with PLEROCEROID within their musclesPLEROCEROID matures into an adult tapeworm within human small intestine (place of residence)
PLEROCEROID matures into an adult tapeworm within human small intestine (place of residence)adult tapeworms attach to intestinal mucosa by means of two bilateral grooves (brothria) of their SCOLEXIMMATURE EGGS are discharged from the PROGLOTTIDS in human feces -->reach fresh water resources --> cycle begins again
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Cestodes Life Cycle (Dipyllidium Caninum)

BeforeCurrentNext
GRAVID PROGLOTTIDS are passed (BUT, REMAIN INTACT) in human/DOG/cat feces or emerge from perianal region of the definitive host (dog or cat or human)Eggs from dog/cat/human feces is ingested by the dog/cat LARVAL FLEA (intermediate host; Ctenocephalides spp.)Once inside the dog/cat FLEA, egg releases an ONCOSPHERE into flea's intestine
Once inside the dog/cat flea, egg releases an ONCOSPHERE into flea's intestineONCOSPHERE within flea intestine penetrates intestinal wall --> enters body cavity --> develops into CYSTICERCOID larvaCYSTICERCOID larva develops into adult and lives within the flea
CYSTICERCOID larva develops into adult and lives within the fleadefinitive host (cat/dog) ingests contaminated flea containing the CYSTICERCOID --> cycle repeats....OR human is accidental host via ingestion of CYSTICERCOID-contaminated fleas (usually via child's close contact with infected dogs/cats; rest of this life-cycle describes this)CYSTICERCOID enters small intestine of human host
CYSTICERCOID enters small intestine of human hostbecomes permanent resident in small intestine via attachment using SCOLEX -->develops into ADULT TAPEWORMADULT TAPEWORM within small intestine produce PROGLOTTIDS which contain two genital pores (aka "double-pored" tapeworm) -->mature into GRAVID PROGLOTTIDS --> released from tapeworm and enter into the human feces (GRAVID PROGLOTTIDS REMAIN INTACT!)
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Cestodes Life Cycle (Hymenolepis diminuta)

General description (he did not cover in class): Eggs are passed in human feces and eaten by arthropods (flour beetles)=>
Humans accidentally ingest the bugs containing infectious CYSTICERCOIDs and the cystericoid larvae are released => Larvae mature and attach to the stomach/intestines releasing eggs=>repeat