Fasciola hepatica - Introduction, Classification, History, Habitat, Morphology

Introduction of Fasciola hepatica

Fasciola hepatica is the causative agent of human fascioliasis. This parasitic trematode is also known as the common liver fluke or sheep liver fluke. The large liver fluke primarily infects the liver of the sheep while humans are the accidental hosts.

History of Fasciola hepatica

In 1379 de Brie first described Fasciola hepatica which is the first trematode - to be described and its life cycle was also demonstrated - in human history.

Adolph Lultz in 1892 described the mode of infection.

Morphology of Fasciola hepatica

The important morphological features of Fasciola hepatica include adult worms, eggs, and the infective form metacercaria.

Adult form

• Fasciola hepatica adult form is large, flat, and leaf-shaped brown

• measures 2.5 cm to 3 cm in length and 1.5 cm in breadth

• the anterior end contains a distinct conical projection and a rounded posterior end

• small oral sucker measuring 1mm in diameter is present in a line

• posterior cephalic cone broadens to form two shoulders

• the alimentary canal is absent – the absence of the anus

• hermaphrodite – contains both sexes with well-developed male and female reproductive organs

• in sheep, the adult parasite can live for 5 years

• in humans, the adult Fasciola hepatica has a lifespan of around 9 years to 13 years

Egg

• large, ovoid, bile-stained

• bile-stained Fasciola hepatica eggs are excreted in the bile into the duodenum

• small and distinct operculum

• measures 130 μm to 150 μm in length and 63 μm to 90 μm in breadth

• unembryonated when freshly passed and further development takes place in the water

• contains a large refractile unsegmented ovum surrounded by a mass of yolk cells

Infective Form

Metacercaria

• Fasciola hepatica metacercaria is the infective form for definitive hosts including humans

• found on the surface of watercress and aquatic vegetation

Epidemiology of Fasciola hepatica

Fasciola hepatica is cosmopolitan in distribution – and infection is much more common in countries with massive sheep and cattle populations.

The liver fluke is specific to tropical areas of Southern Asia, Aouth-East Asia, Africa, Europe, and America. Countrywide, it is more common in Bolivia, Ecuador, Egypt, Peru, UK, France, Spain, and Portugal.