Fasciola hepatica (1) Flashcards
What is the common name?
Liver Fluke
What are the final hosts?
Cattle
Sheep
Goats
Horses
Deer
Man
Other mammals
Humans
What are the intermediate hosts?
Snail
Describe adults
2.5-8.5 cm long
In bile ducts
Leaf shaped
Describe eggs
Up to 130 micro m long
Explain life cycle
Immature eggs in feces, embryonated in H2O
Eggs release miracidia, invade suitable snail
Parasites undergo several developmental stages
- Sporocysts -> Rediae -> Cercariae
Cercariae released, encyst as metacercariae on aquatic vegetation
Herbivores acquire infection ingesting vegetation
Humans infected ingesting plants or metacercariae
Metacercariae encyst in duodenum
Migrate through intestinal wall, peritoneal cavity, and liver parenchyma into biliary ducts to develop into adults
What is the site of infection?
Bile ducts of liver
Describe the Pathogenesis
Immature flukes migrate, feed on liver, rupture liver parenchyma and blood vessels
Fibrosis replaces necrotic tracts
Adults suck blood
Spiny teguments irritate, disrupt mucosa
- Mucosa becomes thickened, dilated, fibrosed - In cattle calcifies
Fluke liberates toxins (contributes to anemia and hyperplasia)
Protein leaks, hypoproteinemia
Acute fasciolosis uncommon in cattle
Chronic fasciolosis - associated with mature flukes
Light infections - growth rate may be impaired
Acquired by grazing on contaminated pastures
Describe heavy infections
Anemia
Pale mucous membranes
Weakness
Weight loss
Submandibular edema (bottle jaw)
Ascites
Anorexia
At necropsy - calcified fibrotic bile ducts (branching network of clay
pipes) “Pipestem” liver
Describe the epidemiology
Several states
Great Britain
France
Algeria
Caribbean
Central America
How do you diagnose?
Eggs in fecal sedimentation
Antibody and excretion/secretion product ELISAs
Necropsy - Adults in liver ducts and gall bladder, black iron-porphyrin
compound in migratory pathways
Quantitative sedimentation
ELISA bulk milk
Elevated:
- Globulin - Albumin - GT
How do you treat and prevent?
Clorsulon - effective against immature/adult flukes
- Cattle must not be treated within 8 days of slaughter
Albendazole (Benzimidazole) - removal of adult liver fluke
Neither drug approved for dairy cattle of breeding age
Flukocides available
Resistance reported
Snail control and management
Triclabendazole
Avoid contaminated pastures
What is important about Fasciola hepatica?
It is ZOONOTIC
