Dicrocoelium dendriticum (D. lanceatum)

Dicrocoelium dendriticum, the lancet fluke of sheep and cattle, a fluke of dry land whose cycle runs through a land snail and an ant it drives to the tips of the grass, and the rare human infection, told apart from eggs that only pass through.

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Checked 28 Oct 2026

Dicrocoelium dendriticum

Point at a name or a part to light it.

Dicrocoelium dendriticum, the lancet fluke, is a slender fluke 6 to 10 mm long that lives in the bile ducts of sheep and cattle. Its organs lie in a different order from those of Fasciola: the testes in front, just behind the ventral sucker, the ovary behind them and the uterus filling the hind part. Its egg, 35 to 45 µm long and dark brown, already holds its miracidium when it is passed; a land snail eats it, cercariae leave the snail in slime balls, and an ant that eats one carries the metacercariae.

Simplified: not to scale: the adult, 6 to 10 mm long, drawn beside forms well under a millimetre; the adult drawn from its ventral side as if cleared, so the organs show through; the nervous and excretory systems are left out, and the place and shape of the testes, the ovary and the yolk glands vary from fluke to fluke; the uterus drawn with fewer loops than it has, and the seminal vesicle and the oviduct left out; the mother sporocyst left out, and the cercariae in the sporocyst and the slime ball drawn few and simple; a slime ball holds thousands.

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Contents3 sections

At a glance

Dicrocoelium dendriticum, the lancet fluke, is a small, slender fluke, 6 to 10 mm long, in the bile ducts of sheep, cattle and other grazing animals; people are infected rarely.
Its organs lie in a different order from those of Fasciola: two testes in front, just behind the ventral sucker, then the ovary, with the uterus filling the hind part. Its caeca are unbranched.
Its life cycle is all on dry land. The egg is passed holding a miracidium and is eaten by a land snail, which sheds the cercariae in slime balls; an ant eats a slime ball and carries the metacercariae.
A metacercaria in the ant's brain makes it cling to the tips of the grass as the air cools, where a grazing animal eats it. People are infected by swallowing an infected ant by accident.
Eggs in the stool after eating infected liver are only passing through, a spurious infection; a stool test after a liver-free diet tells it from a true one.

The lancet fluke

Dicrocoelium dendriticum, also called D. lanceatum, the lancet or lesser liver fluke, lives in the bile ducts and gall bladder of sheep, cattle, goats and other grazing animals, its definitive hosts. It is found throughout Europe, Asia and North Africa, and sporadically in North America; most human cases have been reported from North Africa and the Middle East. Related species are D. hospes, which infects animals and, rarely, people in West Africa, and D. chinensis in East Asia.

Unlike most flukes it needs no water. Its first intermediate host is a land snail and its second an ant, and its definitive hosts are infected by eating the ant.

The adult

The adult is a slender lance, 6 to 10 mm long and 1.5 to 2.5 mm wide, flat and tapering to a point at both ends. It is thin enough that its organs can be seen through it.

Suckers: the oral sucker at the front tip and the larger ventral sucker close behind it, in the front fifth of the body.
Gut: a pharynx and a short oesophagus, which divides in front of the ventral sucker into two simple caeca, without side branches, that run back along the sides and end blindly.
Male organs: two rounded or lobed testes just behind the ventral sucker, one a little behind and beside the other; the cirrus sac in front of the ventral sucker, opening at the genital pore near where the gut forks.
Female organs: a small ovary behind the testes, with Mehlis' gland and the seminal receptacle behind it; the yolk glands in the sides of the middle of the body; and the uterus, which fills the hind part of the body in many loops full of eggs, then runs forward between the testes to the genital pore. Its eggs turn from pale to dark brown as they ripen.

	Fasciola hepatica	Dicrocoelium dendriticum
Size	up to 30 by 15 mm, a broad leaf with a cone in front	6 to 10 by 1.5 to 2.5 mm, a slender lance
Caeca	with many side branches	simple, unbranched
Gonads	ovary in front, branched testes behind it	lobed testes in front, small ovary behind them
Egg	130 to 150 µm, unembryonated	35 to 45 µm, dark brown, embryonated
First intermediate host	pond snail, in water	land snail
Second intermediate host	none: metacercariae on water plants	ant
Way to the bile ducts	through the gut wall and the liver	up the bile duct from the gut

The egg and the larvae

Form	Where	What it is like	What it does
Egg	passed in the faeces	35 to 45 µm by 20 to 30 µm, thick-shelled, dark brown, a little lopsided, with a lid; holds a miracidium	waits on the ground to be eaten by a land snail, in which it hatches
Mother sporocyst	snail, beside its gut	a sac with no mouth or gut	moves to the digestive gland and makes daughter sporocysts
Daughter sporocyst	snail's digestive gland	a slender sac	makes cercariae; there are no rediae
Cercaria	snail, then the slime ball	a young fluke with a tail	gathers in the snail's breathing chamber and leaves it in slime balls of thousands, held in mucus
Metacercaria	ant	a young fluke in a cyst, in the ant's body cavity	the infective form; one or two in the ant's brain change its behaviour

The life cycle

Dicrocoelium dendriticum: the life cycle

Point at a name to light its pathway.

Dicrocoelium needs two intermediate hosts, both on dry land: a land snail, which eats the eggs and sheds cercariae in slime balls, and an ant, which eats the slime balls. Infected ants climb to the tips of the grass and are eaten by grazing sheep and cattle. People are infected only by swallowing an infected ant by accident, which is why human infection is rare.

Simplified: a map, not anatomy: the hosts drawn as icons and the parasites drawn small, nothing to scale; one snail drawn for the many land snails, and one ant for the many ants, that can carry it; the slime ball drawn as a stage of its own, though it is a mass of cercariae; the young flukes' climb up the bile duct drawn as one step.

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The adults in the bile ducts lay eggs that pass with the bile into the gut and out in the faeces, already holding a miracidium. The egg does not hatch on the ground: a land snail eats it, and it hatches in the snail's gut. Many kinds of air-breathing land snail can serve, such as Cochlicopa, Zebrina, Helix and Helicella. The miracidium crosses the gut wall and becomes a mother sporocyst, which moves to the digestive gland and makes daughter sporocysts, in which the cercariae grow. The cercariae gather in the snail's breathing chamber and leave it in slime balls, clusters of thousands held together in sticky mucus.

An ant, usually of the genus Formica, eats a slime ball. Most of its cercariae leave its gut for the body cavity and become metacercariae, the infective form. One or two settle instead in the nerve centre below the ant's oesophagus, the suboesophageal ganglion, and stay unencysted there.

In the sheep or cow that eats the ant, the metacercariae excyst in the small intestine and the young flukes migrate up the bile duct to the smaller bile ducts, where they mature. Unlike Fasciola, they do not cross the gut wall or the liver, which is why the infection does little harm to the liver early on. In lambs, eggs appear in the faeces about 7 to 11 weeks after infection. People are infected the same way, by swallowing an infected ant by accident, with food, which is why human infection is rare.

Dicrocoeliasis

The illness

Dicrocoeliasis in people is usually light and causes no symptoms. Heavier or longer infections cause:

Pain in the right upper abdomen or the epigastrium, nausea, vomiting, and diarrhoea or constipation that can last for weeks.
Inflammation of the bile ducts and the gall bladder: cholangitis and cholecystitis, and sometimes liver abscesses.
Eosinophilia and abnormal liver tests in some.

In sheep and cattle, flukes build up in great numbers, up to 50,000 in a sheep, often with few signs, while long infections thicken the bile ducts and can scar the liver.

Diagnosis

Eggs in the stool: small, dark brown, thick-shelled and embryonated, 35 to 45 µm long, a little lopsided. They are larger and darker than the light, shouldered eggs of Opisthorchis and Clonorchis, and look the same as those of D. hospes and of Eurytrema, a pancreatic fluke of cattle.
True or spurious infection: eggs in the stool may come from the eaten liver of an infected sheep or cow, which pass through unchanged. They are not an infection. A liver-free diet for a few days, then a repeat stool test, tells them apart: in a true infection the eggs are still there.
Serology is available in some laboratories.

Treatment and prevention

Praziquantel, triclabendazole and albendazole have each been reported to clear human infections, but the evidence is only case reports and there is no agreed regimen. In one case a single dose of triclabendazole, 10 mg/kg, was followed by no eggs four weeks later; yet in sheep triclabendazole, the drug for Fasciola, does not work against Dicrocoelium, while albendazole at high doses does.
A spurious infection needs no treatment.

In animals, treating the herd and keeping it off pasture in the early morning and late evening, when infected ants cling to the grass, reduce infection. Controlling the snails and the ants is almost impossible, and chemicals would harm the land.

Check yourselfAnswer, then say how sure you were: a lucky guess still counts as a weak point.

1Which animals are the intermediate hosts of Dicrocoelium dendriticum?

2How do the testes and the ovary of Dicrocoelium lie, compared with Fasciola?

3What happens to a Dicrocoelium egg after it is passed in the faeces?

4How do the young flukes reach the bile ducts after an infected ant is swallowed?

5Dicrocoelium eggs are found in the stool of a person who ate lamb's liver two days ago. What next?

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