Fasciolopsis buski

Fasciolopsis buski egg/CDC

General Information

• Human intestinal trematodiases are associated with eating habits
• They are localized to areas where there is water, snail vectors and reservoir hosts

Geography

• Widely found in rural southeast Asia, in particular central and south China, parts of India and Thailand

Morphology (adults)

• Fasciolopsis buski is the largest fluke to infect humans, aka Giant Intestinal Fluke
• 7.0 x 1.5 cm
• Large, leaf-shaped, lacks a cephalic cone

Morphology (eggs)

• Large, thin-shelled, unembryonated, operculated
• 130-150 x 78-98 um
• Found in large numbers in feces, too similar to F. hepatica to differentiate

Life Cycle

• Adults in the small intestine
• Eggs pass in feces to water where they embryonic
• After few weeks, miracidium emerges
• Miracidium swims to find suitable snail (Segmentina sp.) as first intermediate host
• In the snail-sporocysts>rediae>cercariae
• Cercariae released from snail to water
• Encyst on aquatic plant as metacercariae
• Plant eaten raw by mammalian host (humans and pigs)
• Metacercariae excysts and attach to the gut mucosa
• Develop into adults in about 3 months
• Lives for one year

Pathology

• More worms, more disease- usually asymptomatic
• Large number of worms attaching to mucosa - bleeding, inflammation and ulceration
• Diarrhea (foul smelling greenish-yellow stools), abdominal pain, intestinal obstruction, edema
• Toxic products from worms may be absorbed and cause toxemia
• Death is rare

Diagnosis

• Travel history
• Demonstration of eggs in feces or vomit (eggs indistinguishable from F. hepatica)
• Rarely by identifying adult fluke

Treatment

• Praziquantel is the drug of choice

Epidemiology

• Pigs are reservoir hosts
• Metacercariae encysts on hard surface, particularly water plants like water caltrop and water chestnuts
• The outer cover of plant is peeled off with teeth and metacercariae are released into the mouth
• Children more frequently infected--eat water plants going to and from school

Prevention

• Treatment
• Education
• Changing eating habits- do not eat without boiling first
• Keep pigs from contaminating areas where water plants grow
• Do not feed water plants to pigs

F. buski Life Cycle