Dicrocoelium dentriticum

Phylum Platyhelminthes
    Class Cercomindea
        Order Plagiorchiformes
            Suborder Plagiorchiata
                Family Dicrocoeliidae
                    Dicrocoelium dentriticum

Background

-This parasite is known as a liver fluke.

-Commonly found in the bile ducts of sheep, cattle, goats, and pigs.

Geographic Distribution

-Found in Europe, Asia, North America, and Australia

Definitive Hosts

-Sheep, cattle, goats, and pigs

Intermediate Hosts

-First intermediate host is Cionella lubrica a land snail
-Second intermediate host is Formica fusca an ant

Morphology

-Dicrocoelium dentriticum is 6 to 10 mm long by 1.5 to 2.5 mm in width.
-The body is pointed at both ends.
-It contains an oral and ventral sucker.
-The testes lie directly behind the acetabulum.
-Ovaries lie behind the testes.
-Vitellaria are lateral and are contained in the middle third of the body.
-The eggs contain an operculum.
-Eggs range from 36 to 45 microns by 22 to 30 microns.

Life cycle

-Adult flukes live in the bile ducts within the liver.
-Eggs leave the liver and are passed with the feces.
-The eggs contain a miracidia.
-A land snail must eat the egg before it will hatch.
-In the small intestine of the snail, the egg hatches releasing the miracidia which penetrates the gut wall and develops into a mother sporocyst in the digestive gland.
-Mother sporocysts produce daughter sporocysts which produce cercariae .
-Three months after infection the cercariae accumulate in the lung causing the snail to produce thick mucus.
-The snail eventually expels the cercariae in a slime ball.
-Development of the fluke continues when the cercariae are eaten by the second definitive host an ant.
-An ant will eat the slime ball.
-The cercariae will encyst and be known as a metacercariae.
-Metacercariae are infective to the definitive host.
-Metacercariae that enter the subesophageal ganglion of the ant will change it's behavior .
-In the evening the ants will crawl onto a blade of grass and hang from it's mandibles.
-When the temperature warms up the ant returns to normal behavior.
-On the grass the ant is susceptible to the definitive host during grazing.
-Once eaten by a definitive host the metacercariae excysts in the duodenum.
-It will migrate to the bile ducts and into the liver, mature and produce eggs.

Pathogenesis

-No damage occurs to the gut wall or liver parenchyma
-There is biliary dysfunction
-Anemia results from heavy infections
-The bile ducts become inflamed and edema results
-Fibrous tissue production occurs following inflammation of the bile ducts 
-Bile can back up, decreasing the function of the liver leading to cirrhosis and jaundice
-Migrating juveniles produce ulcers in the eye, brain, skin, and lungs
-Humans can be infected upon eating infected raw liver from sheep and cattle

Diagnosis

-Detection of eggs in the feces

Treatment

-Benzimidazoles
-Praziquantel is effective for domestic animals and humans

Control

-Control is difficult due to the large populations of land snails and ants
-Avoid eating raw or undercooked sheep or cattle liver

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This page was last modified on January 26, 2004
Send questions and comments to Kim Bates