Dicrocoelium dendriticum Presentation By Kristi Bjerke & Heather Lee

Dicrocoelium dendriticum

Presentation ByKristi Bjerke

& Heather Lee

Background

• Digenean trematode• Part of the Dicrocoeliidae family of

liver flukes• Commonly known as the “lancet

fluke” because of its bladelike shape.

• “small liver fluke”

Morphology

• 6-10 mm long• 1.5-2.5 mm wide• Pointed ends

Geographic Distribution

• Most of Europe and Asia• North America• South America• Australia• North Africa• alkaline soils that are favorable

environments for reproduction and survival of the intermediate hosts

Hosts

• Definitive Host: sheep, cattle, goats, pigs, other ruminants, occasionally dogs, horses, and rabbits, rarely humans– Lives in the bile duct and gall bladder

• Intermediate Host: snails, ants

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Life Cycle

• Indirect• Approximately 6 months• Begins when a snail eats the parasite

eggs• The eggs have miracidia which hatch

and then penetrate the snail’s intestinal wall.

• Within the digestive gland, the miracidia transforms into a mother sporocyst.

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Life Cycle Cont.• Mother sporocysts produce daughter

sporocysts.• Second generation daughter

sporocysts develop into cercariae• 3 months later, cercariae build up in

the “lung” of the snail.• The snail deposits the cercariae (5,000) in a slimeball.

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Life Cycle Cont.• An ant eats the slime ball.• Metacercariae form within the ant’s abdominal

cavity.• They then encyst and become infective to the

definitive host. • One or two cercariae travel to the brain which

causes a cataleptic cramp.• The cramp paralyzes the ant on a tip of grass

when temperatures get below 15ºC.• This makes the ant more likely to be eaten by

a ruminant.

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Life Cycle Cont.

• After the ant is eaten, the metacercariae excyst in the gut of the definitive host.

• They migrate to the bile duct and then the gall bladder.

• Here they develop into mature flukes.• The flukes reproduce via cross

fertilization or hermaphroditism• Eggs are released through the host’s

feces.

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Life Cycle Diagram

Pathogenesis

• Hard to reproduce the life cycle in experiments

• In the field there is often infection with other types of parasites with similar symptoms

Pathogenesis continued

• No penetration of the gut wall, liver capsule, or liver parenchyma as in fasciolosis

• Clinical symptoms are not usually manifested even in heavy infections

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• However they may show anemia, edema, emaciation,and in advanced cases, cirrhosis, and scarring of the liver surface

Diagnosis• adult dicrocoelia

recovered in the liver post mortem

• egg coprological (fecal) examination – Releasing of eggs

can take 49-79 days upon infection

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Newer Diagnostic Techniques

• Immuno-diagnostic techniques

• Immuno-flourescence precipitation

• Passive haemoagglutination test

• Complement fixation• ELISA• All try and detect anti-

Dicrocoelium antibodies

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Treatment

• Anti-helminthic drugs like benzimidazole and pro-benzimidazole derivatives

• As of 2002 no possible vaccines have been studied even though an anti-body dependent response has been found

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Control

• Husbandry practices (don’t allow to graze at night or early in the morning)

• Try and control snail and ant populations (difficult/expensive)

• Test the soil to see whether it could be suitable for the intermediate hosts

References• D. Otranto and D. Traversa. A review of dicrocoeliosis

of ruminantsincluding recent advances in thediagnosis and treatment. Veterinary Parasitology 107 (2002) pp 317-335

• http://workforce.cup.edu/Buckelew/dicrocoelium_dendriticum_is_a_bi.htmhttp://www.ilri.org/InfoServ/Webpub/Fulldocs/X5492e/x5492e04.htm

• http://www.spaltudaq.com/• http://commons.wikimedia.org/wiki/

Image:Benzimidazole_simple_structure.png• http://www.princetonol.com/groups/iad/bell/seddon.html• Janovy, John Jr. and Roberts, Larry S., Foundations of

Parasitiology, 7th Edition, 2005

THE END!