Dicrocoelium dendriticum (Lancet fluke)
Veterinary & Aquatic Services Department, Drs. Foster & Smith

Although widely distributed in Europe, D. dendriticum has only been a problem in New York and Pennsylvania in the United States. It is primarily a fluke of herbivores, but it can rarely infect dogs and humans. Commonly called the lance fluke, we suggest it could also be called the 'slime ball fluke' - read on.

What is the life cycle of D. dendriticum and how do 'slime balls' fit in?

D. dendriticum eggs are passed in the feces and eaten by land snails. The eggs hatch and develop into immature forms in the snail. The snail makes and passes slime balls that contain many of these immature forms. The slime balls stick to vegetation and are considered a delicacy by ants. When the immature forms are ingested by an ant, the infective forms develops in the ant's intestines. Infected ants act a bit peculiar. Instead of going to bed at night, they remain attached to the tips of grass to pass the evening hours. These ants are much more likely to be eaten by early morning grazers. When eaten, the infective forms penetrate the intestine of the animal and migrate to the bile ducts.

What are the signs of an infestation with lancet flukes and how is it diagnosed?

Unless there are large numbers of flukes, there are generally few signs of infestation. If large numbers are present, cirrhosis can develop along with anemia and emaciation. A diagnosis is made by finding the eggs of D. dendriticum in the feces of infected animals. However, in the case of dogs, it needs to be verified that the eggs came from the dog's liver and not from some infected liver the dog may have eaten.

How are infestations treated and prevented?

Albendazole at a one-time dose of 7-9 mg/lb. has been shown to be effective in treating infestations with the lancet fluke. Since D. dendriticum infestations are so rare in dogs, precautions generally do not have to be taken.

As many as 14,000 adult lancet flukes can be found in a single sheep.
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