Fascioloides magna (1) Flashcards
What are the definitive hosts?
White-tailed deer
Wapiti
Caribou, etc.
What are the dead-end hosts?
Cattle
Moose
Sika deer
Bison
What are the aberrant hosts?
Sheep
Goats
Horses
Pigs
Roe deer
What is the intermediate host?
Snail
Describe adults
10 cm long
Large
Oval
Describe eggs
Up to 150 micro m long
Explain the life cycle
Juvenile flukes wander aimlessly and destructively in liver tissue
FH - a fibrous cyst forms around fluke, usually in pairs
Mature to adults and lay eggs
Cyst has hole - allows eggs to enter bile
Eggs found in feces with fecal sedimentation
In cattle, bison, and other dead end hosts, cyst forms limiting damage
- No hole in cyst so eggs never enter bile
In AH, cyst never forms
- Damage from meandering immature stages, Host dies
Unembryonated eggs pass in feces
Embryonated eggs in water
Miracidia hatch, penetrate snail
Snail development
- Sporocysts -> Rediae -> Cercariae
Leave snail
Free-swimming Cercariae encyst on water plants
Metacercariae on water plant ingested by human, sheep, or cattle
Encyst in duodenum
Adults in hepatic biliary ducts
Definitive hosts: cyst forms around fluke, develop to adults which lay
eggs
What is the site of infection?
Adults in liver
Describe the Pathogenesis
Infected livers condemned - Economic loss
Deer and cattle - parasite encapsulated by host minimizes clinical
effects
Sheep and goats - continuous migration of immature flukes results in
death before patent infection
How do you diagnose?
Infected livers condemned
Definitive hosts - eggs detected
Dead end and aberrant hosts - eggs not detected
How do you treat and prevent?
Clorsulon
Anthelmintics effective, but not approved in USA
Snail control
In areas where deer are natural reservoir, the land may be unusable for grazing of deer and livestock together
What are the common names?
Deer fluke
Large American Liver Fluke
