Dicrocoelium dendriticum

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Dicrocoelium dendriticum

• Kingdom: Animalia• Phylum: Platyhelminthes• Class: Trematoda• Order: Plagiorchiida• Family: Dicrocoeliidae• Genus: Dicrocoelium• Species: D. dendriticum

• Small flukes which inhabit the bile ducts of a wide variety of mammals

Dicrocoelium dendriticum

• Small flukes which inhabit the bile ducts of a wide variety of mammals

Dicrocoelium dendriticum

• Geographical Distribution:– North/Central/South America– Europe– Asia– North/Central Africa

*Favors Dry Conditions*

• Definitive Host:– Domestic and wild

cattle, sheep, goats– Humans

• Intermediate Host:– 1st: Land snail

(Cionella lubrica) – 2nd: Ant (Formica

fusca)

Pop Quiz #1

1. Name one country this particular parasite is found.(North/Central/South America, Europe, Asia, or North/Central Africa)

2. Name two definitive hosts for this parasite.(Cattle, sheep, goats, or humans)

Morphology

• Adult: 6-10mm by 1.5-2.5mm• Egg: 36-45µm by 22-30µm

Life Cycle

Life Cycle

a.) Adult

b.) Egg

c.) Miracidium

d.) Daughter sporocyst

e.) Mature Cercariae

f.) slime-balls

g-h.) transformation to metacercariae

Life within the Snail

• Eggs released in definitive host’s feces• Snail eats• Miracidium hatches from egg in intestine and

penetrates gut wall• Transformation to mother sporocyst• Produce 1st and 2nd generation daughter

sporocysts with cercariae through asexual reproduction

• Cercariae accumulate• Cercariae escape through snail’s slimeballs

Life within the Ant

• Ant eats the cercariae-containing slime ball• Transform to metacercariae which encyst

– Most remain in the hemocoel– 1 or 2 migrate to subesophageal ganglion,

“brainworms” (these are not infective)

• Alter ant’s behavior– When temperatures drop in the evening ants climb to

the tops of grasses/plants.– Mandible muscles spasm and lock onto the plant– Remain there till they are either eaten or the

temperature warms and they resume normal behavior

Life within the Definitive Host

• Infected ant is eaten by the host

• D. Dendriticum excysts in the duodenum

• Migrates upstream to the common bile duct and then the liver

• Flukes mature in about 6 or 7 weeks

• Reproduce by hermaphroditism or cross insemination

• Eggs are produced and released in feces

Pop Quiz #2

1. What is the order the intermediate hosts come into play in this parasite’s life cycle?(First the snail, then the ant)

2. What makes this parasite unique?(It alters the behavior of the ant)

Pathogenesis/Clinical Signs

• If present in small numbers, parasite does not have much affect on host

• In severe cases when parasite is present in large numbers, following symptoms may occur:– Cirrhosis of liver (leading to decreased function)– Anemia– Edema– Emaciation

• Appears to be no immunity

Diagnosis

• Fecal floatation is one way to diagnose whether or not the parasite is present; however, the eggs are very small and not readily identified because they do not float well

• Usually found at slaughter (find adults in liver)

Treatment• Products:

– Valbazen– Thiabendazole– Triclabendazole– Albendazole – humans– Praziquantel – not in food animals

• No treatment has been proven effective

Prevention/Control

• Treat all animals exposed to infection (two or three times a year)

• Control Intermediate Hosts– Calcium cyanamide molluscicide and chemical

fertilizers• High costs• Ecological effects

– Introduce turkeys, chickens or ducks to eat snails/ants

– Cover ant nests with tree branches• Infected ants are generally found within 30 to 50 cm from

their nest.

Prevention/Control

• As humans we should avoid the urge to nibble or suck on grass which may have ants on it.

Public Health Concerns

• Unless severe liver changes occur; infected animal is still edible

• Humans have been infected but it is very rare

• Economic losses seem less in D. dendriticum than in other flukes

• Reports of Dicrocoeliosis have increased worldwide in the past 20 years

Pop Quiz #3

1. Why is a fecal floatation not the best way to diagnose this parasite?(The eggs are small and do not float very well)

2. There is only one drug that is effective in getting rid of this parasite. True or False?(False – no drug has been proven effective)

References• Associate Database. Dicrocoeliosis. Article obtained February, 12, 2007.

http://www.vin.com/Members/Associate/Associate.plx?DiseaseId=1499

• Dicrocoelium dendriticum – The Lancet Fluke. Dr. Chrissy O’Neill’s notes

• Peacock, Dr. Andrew. Dicrocoelium dendriticum – The Lancet Fluke of Sheep. Published by Newfoundland and Labrodor Agriculture on April 14, 2004. Article obtained February 12, 2007. http://www.nr.gov.nl.ca/agric/animal_diseases/domestic/pdf/dicro.pdf

• Wikipedia. Dicrocoelium dendriticum. Obtained February 12, 2007.

http://en.wikipedia.org/wiki/Dicrocoelium_dendriticum

• Otranto, D., & Traversa, D. (2002/8/22). A review of dicrocoeliosis of ruminants including recent advances in the diagnosis and treatment. Veterinary Parasitology, 107(4), 317-335.

• Otranto, D., & Traversa, D. (2003/1). Dicrocoeliosis of ruminants: A little known fluke disease. Trends in Parasitology, 19(1), 12-15.

• Schmidt, G., & Roberts, L. (2005). Foundations of Parasitology (7th ed.). New York, NY: McGraw-Hill.