Clonorchis sinensis - Classification, Habitat, Morphology, Epidemiology, Transmission

Introduction of Clonorchis sinensis

Clonorchis sinensis, commonly known as liver fluke or the Chinese liver fluke, infects the common bile duct and gall bladder of fish-eating mammals such as humans. These parasites, which are the causative agent of clonorchiasis, feed on bile and are one of the most important liver fluke infecting humans.

Classification of Clonorchis sinensis

Kingdom: Animalia

Phylum: Platyhelminthes

Class: Trematoda

Order: Plagiorchiida

Family: Opisthorchiidae

Genus: Clonorchis

Species: C. sinensis

History of Clonorchis sinensis

The Clonorchis sinensis was first discovered by British physician James McConnell in 1874 at the Medical College Hospital in Calcutta, India. The parasite was found in the bile duct of a Chinese carpenter.

In 1927, the life cycle of the liver fluke was discovered by Faust and Know.

Habitat of Clonorchis sinensis

The adult worm of Clonorchis sinensis habitats the distal biliary passages and pancreatic ducts of man, domestic animals as well as wild animals.

Morphology of Clonorchis sinensis

The important morphological stages of Clonorchis sinensis include the adult, eggs, and metacercaria.

Adult worm

• the adult worm of Clonorchis sinensis is oblong, flat, and transparent with a rounded posterior end and pointed anterior end

• small in size measuring 10mm to 25mm in length and 3mm to 5mm in width

• oral sucker slightly larger than the ventral sucker

• ventral sucker located in the posterior part of the anterior third

• the posterior third of the body contains two large testes which are deeply lobulated and branched

• the uterus which is located anteriorly is the identifying feature of Clonorchis sinensis

• the lifespan of the fluke is between 20 years to 30 years

Eggs

• Clonorchis sinensis eggs are small, flask-shaped with an operculum at the small anterior part

• bile-stained i.e. yellowish brown

• measures 28μm to 35μm x 12μm to 18μm

• the posterior end has a small knob that gives an appearance of an electric bulb

• the eggs are fully embryonated when laid and contain a ciliated embryo called miracidium

• are passed along with the host feces

• infectious only to snails but not humans or other mammals

Infective form

Metacercaria

• the infective form of Clonorchis sinensis

• found encysted in the flesh of fresh-water fish

Epidemiology of Clonorchis sinensis

Epidemiological studies of Clonorchis sinensis have confirmed the endemic regions to be in Japan, China, Vietnam, Taiwan, South Korea, and Hong Kong.

Reservoir, Source of Clonorchis sinensis

The source of Clonorchis sinensis infection is raw freshwater fish infected with metacercaria.

An important reservoir of Clonorchis sinensis is humans and dogs. Feces from infected individuals contaminate freshwater sources.

Transmission of Clonorchis sinensis

Transmission of Clonorchis sinensis takes place by the following sources:

• consumption of raw, partially cooked, dried, salted, pickled fish infected with the fluke