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Trematodes
Fichas del conjunto (17)
- 1TrematodesPhylum PLATYHELMINTHES
Dorsally flattened
1.1 billiom people worldwide at risk from food borne trematode infections
Particularly in SE asia amd westerm pacific region - 2Opisthorchis (clonorchis) sinensis ABOUT20-30m people infected ww
2cm adult length
Main foci: SE Asia, japan, korea, thailand, china
Causes OPISTHORCHIASIS
Causes diarrhoea and abdominal pain - 3Fasciola hepatica ABOUTLargely a parasite of livestock
2.4-17m people infected
Ww distribution:
Bolivia, portugal, iran, france, egypt
Occurs in bile duct
Plant based - 4Paragonimus westermani ABOUT21m people infected
Occurs in Asia (china, korea, india, japan, phillipines, sri lanka, taiwan, thailand, vietnam) central west africa, s america
Adult 8-16mm in length - 5Schistosomes ABOUT200m infected
Blood fluke
Live in blood vessels in specific sites in body
America, asia, s.america - 6Types of schistosomesSchistosoma mansoni (intestinal)
Schistosoma japonicum (intenstinal)
Schistosoma haemotobium (urinary) - 7Opisthorchis sinensis lifecycleHuman eats raw or undercooked fish infected with METACERCARIAE
Excysts in the duodenum within 3-4 weeks
Migrates to biliary duct and becomes adult
Human defecates fully developed and embryonated eggs (requires freshwater)
Snails ingest eggs (bithynia spp)
Inside snail, eggs release miracidia which penetrate intestinal wall amd sporocysts develop within haemocoel cell
Rediae then develop within 17 days and wthin 30 days, the ciliated cercariae are released.
CERCARIAE penetrate 2nd intermediate host - cyprinid fish (carp)
Encyst on skin or flesh and turn into METACERCARIAE - 8Paragonimus westermani LIFE CYCLEHumans ingest inadequately cooked or pickled crustaceans containing METACERCARIA
Excyst in duodenum
Penetrate through intestinal wall
Then enters diaphragm via thoratic cavity
Excreted unembryonated in sputum by being spat out
Or swallowed and passed out in stool
Eggs become embryonated and hatch in 7-21 days to release MIRACIDIUM
Miracidia hatch and seek first intermediate host, a semisulcospira snail species
Approx 1 month in snail
Sporocysts -> redia -> daughter redia -> cercariae
Penetrates heart and muscle of second intermediate host crustacean (crab or crayfish)
Cercariae invade crustaceam amd encyst into metacercariae.
Infective after 23 days - 9Fasciola hepatica LIFECYCLEHuman or ruminant ingests infective metacercariae
Metacercariae resistant to stomach ph
Excysts in small intestine wall and migrates to liver
Takes about 7 days
Excysts in duodenum, migrates through intestinal wall
Burrows through bowels to reach bile duct
Matures into adult in biliary duct, where it can live for 25 years
Unembryonated eggs passed in feces
Become embyonated in water
Eggs release MIRACIDIA penetrate and invade a snail IM host
Undergoes several developmental stages in snail
Sporocyst-> reduae-> occasional daughter rediae if if emviro conditions are adverse -> optimal contion 10 degrees reached, CERCARIAE
Reased 5-6 weeks after infectiom and encysts in water plants (mint or watercress)
Developes into METACERCARIAE and infects host - 10Natural/manmade water bodiesIRRIGATION SYSTEMS
DAMS - 11Irrigation schemesBrings water into fields flooding and aiding transmission
F.hepatica require vegetation for metacercariae to develop on
If IS werent utilised, it would prevent cercariae from moving from mollusc host - 12DamsBuilding w/o proper planning allows snails to populate the water = host
Concerns in china over 3 gorges dams causing an increase in f-b-t infections
Fish and crustaceans occur in close proximity to snails = hosts
Prope planning would prevent miracidia from infecting - 13Water conditionsVelocity
Temperature
Soil conditions
Water current
Water quality
Important roles in formation of suitable habitats
Some trematodes prefer polluted water (min ho, 2004)
F.hepatica require clean weater - 14Night soilProblematic
May contain trematode eggs
Prevent usage of night soil, prevent transmission - 15What requires aquatic transmission?Mollusc
Fish
Crustacean
Metacercariae
Unembryonated egg - 16A study foundA 2.15 rold increase in f.b.t. Inf tiom when freshwater bodies are in close proximity to house
- 17Schistosoma LIFECYCLESWIMMERS ITCH
CERCARIAE penetrates human skin and loses its forked tail, becoming a SCHISTOSOMULAE
Migrates to blood in liver and matures into adult
Paired adults migrate to bowel and female deposits eggs
Shed i human feces, or urine
Eggs hatch and release MIRACIDIA
Pentrate snail
2 generations of sporocysts
Free oiving in water
Turn into infective CERCARIAE
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- Fichas sobre Trematodes, creado por l.blake el 11/05/2015.
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