Dicrocoelium dendriticum
A parasitic fluke with a life cycle involving snails and ants.
Dicrocoelium dendriticum, the lancet liver fluke, is a parasitic flatworm that primarily infects the bile ducts of grazing mammals such as cattle, sheep, and goats. Its complex life cycle involves two intermediate hosts—a land snail and an ant—and it can occasionally infect humans. The species was first discovered by Rudolphi in 1819, but its full life cycle was not understood until the work of naturalist Wendell Krull and C.R. Mapes in the early 1950s.
- first_intermediate_host
- Many species of land snails (e.g., Cochlicopa lubrica)
- second_intermediate_host
- Multiple ant species in the genus Formica (e.g., Formica fusca)
- prepatent_period
- 6 to 7 weeks (42 to 49 days)
Quick Facts
- Genus
- Dicrocoelium
- Species
- dendriticum
Facts from the source article.
Lore & Background
Much of what is presently known about Dicrocoelium dendriticum is the result of the work of the naturalist Wendell Krull. While the species was discovered by Rudolphi in 1819, the full life cycle was not known until Krull and C.R. Mapes published a series of papers from 1951 to 1953 detailing their observations and experiments. It was known that D. dendriticum infected sheep, but everything else was a mystery. The first link in the chain was the discovery that many species of land snails can serve as the first intermediate host (e.g., Cochlicopa lubrica). Next came the discovery that the slime balls coughed up by the snails could be a potential method of transfer of the parasite. Shortly thereafter, multiple ant species in the genus Formica (e.g., Formica fusca) were found to be the second intermediate host by which sheep were infected.
Reader's Guide
Dicrocoelium dendriticum is significant as a model of complex parasite life cycles and host manipulation. Its life cycle, elucidated by Krull and Mapes, involves a land snail as first intermediate host and an ant as second intermediate host. The parasite alters the ant's behavior, causing it to climb grass blades at dusk and clamp its mandibles, increasing the chance of ingestion by grazing mammals. This fluke can infect humans, though rarely, typically through ingestion of infected ants. In ruminants, infections are often sub-clinical but can cause liver lesions and cirrhosis. Diagnosis traditionally relies on egg detection in feces, but bile or duodenal fluid examination is more accurate in humans. Treatment includes anthelmintics such as Praziquantel. The parasite is endemic in over 30 countries, favoring dry, chalky, alkaline soils. Its inclusion in WHO's Foodborne Disease Burden Epidemiology Reference Group highlights its public health relevance.
Did You Know?
- The lancet liver fluke's life cycle was fully described by Wendell Krull and C.R. Mapes in papers published from 1951 to 1953.
- The parasite manipulates the ant host's behavior, causing it to climb grass blades and clamp its mandibles in a trance-like state; the timing and duration of this behavior can vary and is not strictly until dawn in all d
- Human infections are rare and often result from ingesting infected ants, such as in a case involving bottled water contaminated by ants.
- Dicrocoelium dendriticum is found in Europe, Asia, Africa, the Americas, and Australia, favoring dry, chalky, alkaline soils.
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