Phylum Platyhelminthes, Order Trematoda Flashcards
What are the general features of Platyhelminthes?
Dorso-ventrally flattened Bilaterally symmetrical No cavity Contain parenchyma --> organs embedded in it Digestive tract incomplete / absent - use nutrients from host Contain hooks / suckers Hermaphrodites No cuticle
What are the general features of Trematoda (Flukes)?
Have oral and ventral suckers
Operculated eggs (lids)
Contain at least 1 IH
Majority is endoparasites
What are the general features of Trematoda, Subclass Digenea?
Endoparasites
Always contain a ventral sucker
Digestive system incomplete - no anus
Contains oral sucker, mouth, pharynx, oesophagus and caeca (holds digested blood)
Hermaphroditic
Male parts - contain testes
Female parts - contain ovary, uterus, vitelline glands
What are vitelline glands?
produce vitelline cells, and carry the cells tothe oviduct which produces eggs and nutrients for the eggs
What is the typical lifecycle for Trematoda, subclass Digenea?
IH = Molluscs (gastropods)
Asexual multiplication occurs within IH to produce large numbers of free living larvae
Adult –> egg –> miracidium –> sporocyst –> (redia) –> cercaria –> metacercaria –> adults
Stages:
- Adult within DH
- Operculated eggs shed in environment
- Miracidium develop and invade the IH (ciliated)
- Sporocyst within IH
- Redia within IH - are enlongated
- Cercaria within IH and then shed into the environment - contain tail - will infect DH or go into metacercaria
- Metacercariae is the encyst form of cercaria sit on pasture. After being ingested, mature into adult flukes.
What are the general features of Fasciola hepatica?
Known as liver fluke
Leaf like
Spines over its body
Anterior end is cone shaped then follows with broad shoulders
Oral and ventral suckers
Caeca is branched and extend posteriorly - hard to see
Uterus is yellow (eggs) testes in middle of body
Ovaries are behind uterus
Eggs are yellow, operculated, thin shelled.
Eggs need humidity and favourable temp, O2 to develop
Adults located in bile ducts of hosts
Juveniles travel through the liver
IH = snails
What is the lifecycle of Fasciola hepatica?
Complete development requires eggs to leave faeces, develop to miracidium, miracidium penetrate the snail and form into a sporocyst (within liver of snail) (need IH or will die).
Sporocyst redia develop and cause damage to the snail, form into cercaria (1 miracidium = 4000 cercaria). They then leave the IH and encyst into metacercaria on blades of grass. Can survive long times in metacercaria.
Infection of DH via the ingestion of the metacercaria on the pasture / water. Metacercaria excyst in the SI, and travel to the liver via migrating through body / travelling through blood / ** burrowing through intestine, then burrow through the liver for 2 months causing extensive damage. Feed on hepatocytes and blood
Reach the bile ducts and mature into adults. Feed on blood
Humans can become infected via eating infected liver - not in Aus
What species of trematoda - larval stage infects the liver?
Fasciola hepatica in pigs
What species of trematoda causes high amounts of damage from larval stages burrowing through?
Fasciola hepatica in pigs
What are the general features of Paramiphistomes?
Known as the stomach fluke
In cattle and sheep
Adults located in the rumen and reticulum
Contain anterior and posterior sucker - attaches with posterior sucker (compared to fasciola which attaches with ventral sucker). Thick bodied, pear shaped, vitelline glands, branched testes, caeca, etc.
Juvenile stages located in the duodenum and abomasum –> attached to mucosa and feed on blood and tissues. More pathogenic than adults
Eggs - operculated, pale / greenish. Slightly bigger than Fasciola hepatica
What are two important Paramphistomes (stomach fluke) species for Australia?
Paramphistomum ichikawa
Calicophoron calicophorum
What is the lifecycle of the Paramphistomes?
IH = snails
Similar to Fasciola hepatica
Eggs shed into environment, develop into miracidium within water, invade into IH, develop into sporocyst. Sporocyst develop redia and then form into cercaria. Cercaria exit from the IH and move into environment. Move onto a blade of grass and encyst into metacercaria.
Metacercaria is ingested by DH and they excyst during passage through the stomaches of ruminants –> they attach to the mucosa of the small intestine with the posterior sucker and grow. The juveniles then migrate to the rumen / reticulum where they mature.
What are the main features of Dicrocoelium dendriticum?
Known as the small liver fluke Not in Aus Host - ruminants IH = terrestrial snail and ants Located in the bile ducts and gallbladder Not super pathogenic Smaller thin, spear shaped (lancet) Semitransparent body Anterior and ventral sucker
Eggs are operculated, dark brown, asymmetrical, contain a miracidium with 2 germ balls
What is the lifecycle of Dicrocoelium dendriticum?
Eggs passed in faeces, ingested by snails –> miracidium, sporocyst, redia, cercaria.
Cercaria exit the snail in clusters of more than 5000 enveloped in slime balls
Slime balls are ingested by ants where the cercaria molts to metacercaria
Cercaria within the ant paralyse it once it reaches the tip of the grass.
Ants and metacercaria are ingested with the pasture (ruminants DH). Metacercaria are released from the ants and the juvenile stages are attracted to bile –> move up the bile ducts and mature. Not as pathogenic as they are smaller and do not travel through the liver.
What are the Hosts, location and lifecycle of Opistorchis tenuicollis, Opistorchis viverrini and Clonorchis sinesis.
All located within the bile ducts
O. tenuicollis = humans, dogs, cats, pigs
O. viverrini = humans, dogs cats
C. sensis = humans, dogsm cats, pigs
Eggs passed in faeces, ingested by IH (snails), form miracidia, sporocyst, redia, cercaria. Cercaria leave the host and swim and get ingested by 2nd IH (fish). Cercaria encyst within the fish SC tissues. DH get infected after the ingestion of infected fish. Juvenile travel to liver via bile ducts.
