Trematodes I Flashcards
What are the life stages of trematodes?
Adult Egg Miracidium Sporocyst/Redia Cercaria Metacercaria (becomes adult)
Describe adult trematodes
Found in the DH Size varies Pair of suckers (oral and ventral) Monoecious (there are exceptions) Egg laying stage Hermaphroditic
Where does the miracidium emerge from the egg?
Operculum
What stage of trematodes emerges from mollusks?
Cercaria
What is the encysted stage of the trematode life cycle?
Metacercaria
What are metacercaria encysted in?
Environment or in an intermediate host
What is Fasciola hepatica?
Liver fluke
Liver rot
Fascioliasis
What is the DH of Fasciola hepatica?
Ruminants
Pigs
Horses
Wide range of mammalian wildlife
What is the IH of Fasciola hepatica?
Lymnaeid snails
What do Fasciola hepatica metacercariae encyst on?
Vegetation
What is the site of Faciola hepatica in DH?
Bile ducts, liver
What is the life cycle of Faciola hepatica?
Definitive host ingests metacercariae
Excyst in SI; juvenile fluke penetrates gut; abdominal cavoty to liver
Liver migration
To bile duct and matures to adult
Unembryonated eggs in bile to intestine; shed in feces to water in environment
Miracidia hatch in water
Penetrates lymnaeid snail, undergoes asexual reproduction
Cercariae emerge, attach to vegetation and encyst as metacercariae
What is the pathology associated with Fasciola hepatica immature flukes?
Hepatitis
Fibrotic tracts
Hemorrhage
Anemia
What is the pathology associated with Fasciola hepatica adults?
Anemia Proliferation of bile duct epithelium Cholangitis Necrosis of duct walls Fibrosis
How does acute disease with Faciola hepatica occur?
Ingest large numbers of metacercariae
What is the subacute form of Fasciola hepatica?
Massive infections; accumulated infections over time
What is the chronic form of Fasciola hepatica?
Moderate infection
How do you diagnose Fasciola hepatica eggs?
Fecal sedimentation
Oval, operculated, yellow
Where are Fasciola hepatica juveniles found?
Liver parenchyma
Can Fasciola hepatica infect humans?
Yes, but it is rare
What is the DH of Fascioloides magna?
Primarily cervids (especially white tailed deer)
What is the site of Fascioloides magna in the DH?
Bile ducts, liver
What is the IH of Fascioloides magna?
Lymnaeid snails
What is the site of Fascioloides magna metacercariae?
Vegetation
What are the aberrant hosts of Fascioloides magna?
Sheep, goats
What are the accidental/incidental/dead-end hosts for Fascioloides magna?
Cattle Pigs Llamas Horses Moose
What is the life cycle of Fascioloides magna?
DH ingests metacercariae
Excyst in SI; juvenile fluke migrates in abdominal cavity
To liver: extended migration
Matures to adults encysts in bile ducts (pairs)
Unembryonated eggs in bile to intestine, shed in feces to water in environment
Miracidia hatch in water
Penetrates lymnaeid snail; undergoes asexual reproduction
Cercariae emerge, attach to vegetation; form metacercariae
What is the pathology of Fascioloides magna in cervids?
Flukes in thin-walled cysts
Eggs leave cysts by channels to bile duct
What is the pathology of Fascioloides magna in accidental hosts?
Unapparent
Closed cysts
No trematode ova in feces
Liver condemned
What is the pathology of Fascioloides magna in aberrant hosts?
Uninterrupted migration
No cysts, adults or eggs
Highly pathogenic, traumatic hepatitis
What are the methods of diagnosing Fascioloides magna?
Eggs detected by sedimentation
Adults encysted in liver
How is Fascioloides magna diagnosed in cattle?
Usually encapsulated
Dead or empty calcified capsules
How is Fascioloides magna diagnosed in sheep and goats?
Adults not present
Severe liver damage
What is the DH of rumen flukes- Paramphistomidae?
Cattle, goats, sheep
What is the site of rumen flukes- paramphistomidae?
Rumen and reticulum
What is the IH of Paraphistomum?
Aquatic snail
Is Paraphistomum pathogenic?
Not usually, but it is more pathogenic in young
Where is the metacercariae of Paraphistomum?
Vegetation
What is the life cycle of Paraphistomum?
DH ingests metacercariae
Excysts in upper SI
Juveniles migrate to abomasum to reticulum to rumen
Matures to adults in rumen
Unembryonated eggs passed in feces
Miracidia hatch; penetrate aquatic snail; asexual reproduction occurs
Cercariae released
Cercariae encyts; form metacercariae on vegetation
How are Paraphistomum adults diagnosed?
In rumen/reticulum
Usually incidental finding at necropsy
How are Paraphistomum eggs diagnosed?
Sedimentation
What is Dicrocoelium dendriticum?
Lancet fluke
Little liver fluke
What is the DH of Dicrocoelium dendriticum?
Sheep, cattle, goats
What are the primary sites of Dicrocoelium dendriticum in the DH?
Liver
Gall bladder
Bile ducts
What is the 1st IH of Dicrocoelium dendriticum?
Land snail
What is the 2nd IH of Dicrocoelium dendiriticum?
Metacercariae in ants
What is the life cycle of Dirocoelium dendiriticum?
DH ingests ant with metacercariae
Excyst in SI; juvenile fluke migrate through common bile duct to bile ducts and liver
Adults in bile ducts, liver, gallbladder
Embryonated eggs in feces
Eggs ingested by land snail
Miracidia hatches from egg in snail; asexual reproduction occurs
Cercariae released in slime ball
Ants ingest slime ball with cercariae
Metacercariae form in abdomen/brain affect behavior
How do you diagnose Dicrocoelium dendriticum eggs?
Fecal sedimentation
Can Dicrocoelium dendriticum infect humans?
Yes, but it is rare
Accidental ingestion of ant
What is the DH of Platynosomum spp?
Domestic/wild cats
What is the 1st IH of Platynosomum spp?
Land snail
What is the 2 IH of Platynosomum spp?
Isopods (pill bugs), woodlice, cockroaches
What are the 3rd IH/paratenic host of Platynosomum spp?
Lizards, toads, geckos (swallow pill bug)
What is the life cycle of Platynosomum spp?
Cats ingests infected lizard/amphibian with metacercariae
Excyst and move up SI to common bile duct to bile ducts to gallbladder
Adults in cat bile and pancreatic ducts, gallbaldder
Embryonated eggs in feces
Land snail ingests eggs with miracidia; asexual reproduction, cercaria develop
Cercariae are shed in sporocysts
Sporocysts with cercariae ingested by isopods; metacercariae form
Lizard/amphibian ingests isopod with metacercariae
What is the pathology associated with Platynosomum spp?
Cumulative infections
“Lizard poisoning”
Proliferative cholangitis
Cirrhosis
How are Platynosomum spp eggs diagnosed?
Fecal sedimentation
How are Platynosomum spp adults diagnosed?
Ultrasound
Liver biopsy
Necropsy
