Fasciola hepatica
Disease: Fascioliasis (liver fluke disease)
Habitat
- Bile ducts of liver
Morphology
- Large, leaf-shaped fluke (≈ 30 mm × 13 mm)
- Cone-shaped anterior end with oral sucker
- Ventral sucker present
- Highly branched intestinal caeca
- Hermaphrodite
Hosts
- Definitive: sheep, cattle, humans
- Intermediate: freshwater snail (Lymnaea)
Life Cycle
- Eggs passed in feces → hatch in water to miracidia
- Miracidia penetrate snail → sporocyst → redia → cercaria
- Cercariae released and encyst on aquatic plants as metacercariae (infective stage)
- Humans infected by eating raw water plants (e.g. watercress)
- Juveniles migrate through liver parenchyma to bile ducts
Symptoms
- Acute: fever, right upper quadrant pain, hepatomegaly, eosinophilia
- Chronic: biliary obstruction, cholangitis, jaundice
Diagnosis
- Eggs in stool (chronic phase)
- Serology in early infection
Prevention
- Avoid raw aquatic plants
- Control snail population
- Proper washing/cooking of vegetables
Dicrocoelium dendriticum
Disease: Dicrocoeliasis
Habitat
- Bile ducts (does not migrate through liver parenchyma)
Morphology
- Small, lance-shaped fluke
- Less branched intestines than Fasciola
- Hermaphrodite
Hosts
- Definitive: sheep, cattle, humans
- 1st Intermediate: land snail
- 2nd Intermediate: ant
Life Cycle
- Eggs ingested by snail → cercariae expelled in slime balls
- Ant ingests slime balls → metacercariae develop
- Infected ants cling to grass tips
- Humans infected accidentally by eating infected ants with vegetation
- Adults reach bile ducts directly
Symptoms
- Usually mild or asymptomatic
- Chronic biliary irritation
Diagnosis
- Eggs detected in stool
Prevention
- Avoid contaminated raw vegetables
- Control intermediate hosts