Sunday, April 15, 2012

Fasciola hepatica

Fasciola hepatica egg  Photo/CDC

General Information

·         Fasciola hepatica is a trematode or fluke also known as the “sheep liver fluke”
·         All trematodes are parasitic
·         All trematodes have a phase of their life cycle in snail or other molluscan host
·         All trematodes are associated with water
·         Facioliasis is a zoonotic disease

Geography

·         Human infection has been reported from over 60 countries, mainly in sheep-raising areas
·         Important public health problem in Latin America (Peru, Bolivia, Cuba), Russia, parts of Europe and Iran
·         Reported sporadically in the US

Morphology (adults)

·         Leaf-shaped with cephalic cone
·         3.0 x 1.3 cm

Morphology (eggs)

·         Large, ovoid, thin-shelled, operculated, yellowish-brown in color
·         130-150 x 90 um in size

Life Cycle

·         Adult fluke in biliary passages
·         Immature eggs are discharged in feces
·         Eggs embryonate in the water
·         Eggs hatch and release miracidia
·         Miracidia invade suitable snail host (intermediate host)
·         Development in snail (sporocyst>rediae>cercariae)
·         Cercariae leaves snail and encyst on aquatic vegetation as metacercariae
·         Metacercariae on uncooked water plant is ingested by human, sheep or cattle (F. gigantica)
·         Metacercariae excyst in the duodenum
·         Migrates through intestinal tract, peritoneal cavity and liver parenchyma into bile ducts
·         Matures into adults
·         Maturation from metacercariae to adult fluke takes up to 4 months
·         In humans, adult flukes can produce eggs for 9 years

Pathology

·         Migrating flukes can cause abdominal pain, liver enlargement and fever
·         Blockage of bile ducts, portal cirrhosis, eosinophilia, jaundice, diarrhea and anemia
·         Halzoun: In humans that eat raw sheep liver. Adult flukes leave liver and attach to throat causing blockage

Diagnosis

·         In endemic areas, symptoms suggest infection
·         History of eating uncooked watercress and water lettuce
·         Finding eggs in feces or biiary drainage. Eggs of F. hepatica and Fasciolopsis buski too similar to differentiate. Check travel history.
·         Antibody detection: enzyme immunoassays (EIA) with excretory-secretory (ES) antigens combined with confirmation of positives by immunoblot

Treatment

·         The drug of choice is triclabendazole with bithionol as an alternative

Epidemiology

·         Sheep-raising countries (and cattle) where there is a suitable snail host (Lymnea sp).
·         Where humans eat uncooked watercress and other aquatic plants in salads or on sandwiches

Prevention and Control

·         Educate public in endemic areas not to eat wild (uncooked) watercress and other water plants
·         Avoid using livestock feces to fertilize water plants
·         Treat animal infections
·         Using molluskicides

Other Information

·         False fascioliasis (pseudofascioliasis): this is the presence of eggs in the stool resulting not from an actual infection but from recent ingestion of infected livers containing eggs. 
·         Have the patient follow a liver-free diet several days and repeat stool examination. 

Adult Fasciola hepatica  Photo/Adam Cuerden via Wikimedia Commons



1 comment:

  1. that,s so good explanation and comprehensive information

    ReplyDelete