Infectious Disease and Microbiology – Fasciolopsis buski

Overview

Fasciolopsis buski is a large intestinal trematode (fluke) that causes fasciolopsiasis. Unlike Fasciola species, which primarily involve the liver and biliary tract, F. buski primarily inhabits the small intestine.

Infection is concentrated in parts of South and Southeast Asia and usually produces gastrointestinal manifestations. Heavy worm burdens can rarely result in acute intestinal obstruction.

Microbiologic Characteristics

Fasciolopsis buski is:

• A trematode helminth

• An intestinal fluke

• Approximately 7 cm long as an adult

• One of the largest intestinal flukes infecting humans

Adult worms primarily inhabit the small intestine.

Epidemiology

Fasciolopsiasis occurs predominantly in:

• Rural Southeast Asia

• India and other parts of South Asia

Transmission is associated with areas where the parasite’s freshwater life cycle can be maintained.

Transmission

Humans acquire infection by ingesting metacercariae attached to raw or inadequately prepared aquatic vegetation.

Freshwater snails serve as intermediate hosts.

The general transmission cycle is:

Eggs reach freshwater

→

Freshwater snail intermediate host

→

Metacercariae develop on aquatic plants

→

Humans ingest contaminated aquatic vegetation

→

Adult flukes develop in the small intestine

Fasciolopsiasis

The disease caused by F. buski is known as:

Fasciolopsiasis

The severity of disease is related partly to the number of worms present.

Light infections may produce few or no symptoms, whereas heavier infections can cause significant gastrointestinal disease.

Gastrointestinal Manifestations

Clinical manifestations may include:

• Diarrhea

• Constipation

• Vomiting

• Anorexia

• Abdominal discomfort

The parasites can produce local irritation and inflammation of the intestinal mucosa.

Heavy Infection

Heavy parasite burdens can produce more severe gastrointestinal manifestations.

Large numbers of these relatively large flukes may interfere with normal intestinal function.

Acute Intestinal Obstruction

A rare but important complication is:

Acute intestinal obstruction

This is particularly associated with a heavy worm burden.

Thus:

Endemic-area exposure + gastrointestinal symptoms + intestinal obstruction

should raise consideration of heavy F. buski infection.

Diagnosis

Diagnosis is primarily established by:

Parasitologic examination of stool

Characteristic trematode eggs can be detected microscopically.

Stool Examination

Stool microscopy is the principal diagnostic method because adult worms residing in the intestine release eggs that are passed in feces.

The eggs may resemble those of Fasciola species, so clinical and epidemiologic context can assist with interpretation.

Treatment

The source recommends:

Praziquantel 25 mg/kg orally every 8 hours for 1 day

Praziquantel is the major antiparasitic agent associated with treatment of fasciolopsiasis.

Additional Treatment

The source lists:

Niclosamide 2 g orally as a single dose

as an additional treatment option.

Prevention

Prevention centers on interrupting transmission from contaminated freshwater environments.

Important measures include:

• Avoiding raw aquatic vegetation in endemic areas

• Thoroughly cooking aquatic plants

• Safe sanitation and disposal of feces

• Avoiding contamination of freshwater sources

Fasciolopsis vs. Fasciola

Fasciolopsis buski

→ Intestinal fluke

→ Adult worms live in the small intestine

→ Causes fasciolopsiasis

→ Diarrhea, vomiting, anorexia, and possible intestinal obstruction

→ Praziquantel is the classic treatment

Fasciola hepatica / F. gigantica

→ Liver flukes

→ Primarily involve the liver and biliary tree

→ Cause fascioliasis

→ Hepatic migration may produce RUQ pain and eosinophilia

→ Triclabendazole is the key treatment

High-Yield Clinical Pattern

Patient from rural Southeast or South Asia

• ●

Consumption of contaminated aquatic vegetation

• ●

Diarrhea, vomiting, anorexia, or abdominal symptoms

• ●

Large intestinal trematode eggs in stool

→ Think Fasciolopsis buski

Severe Infection Pattern

Heavy intestinal fluke burden

• ●

Acute abdominal symptoms

• ●

Mechanical intestinal obstruction

→ Consider severe Fasciolopsis buski infection

Exam Essentials

Organism: Fasciolopsis buski

Type: Trematode helminth

Common name: Large intestinal fluke

Adult size: Approximately 7 cm

Distribution: Rural Southeast Asia and South Asia

Primary site: Small intestine

Transmission: Ingestion of metacercariae on aquatic vegetation

Intermediate host: Freshwater snail

Disease: Fasciolopsiasis

Major symptoms: Diarrhea, constipation, vomiting, anorexia

Major rare complication: Acute intestinal obstruction

Diagnosis: Parasitologic stool examination

Treatment: Praziquantel 25 mg/kg every 8 hours for 1 day

Alternative in source: Niclosamide

Key clinical pearl: Fasciolopsis buski is a large intestinal fluke acquired from contaminated aquatic vegetation; remember small-intestinal disease + gastrointestinal symptoms + possible obstruction, in contrast to Fasciola species, which primarily cause hepatic and biliary disease.